thodg/libgit2

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 23c5af1..918e5b8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -305,6 +305,11 @@ ELSE ()
 	ENDIF ()
 	IF (APPLE) # Apple deprecated OpenSSL
 		SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-deprecated-declarations")
+
+		# With clang, disable some annoying extra warnings
+		IF (NOT CMAKE_COMPILER_IS_GNUCC)
+			SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-unused-const-variable -Wno-unused-function")
+		ENDIF()
 	ENDIF ()
 	IF (PROFILE)
 		SET(CMAKE_C_FLAGS "-pg ${CMAKE_C_FLAGS}")
diff --git a/include/git2/index.h b/include/git2/index.h
index dd6a28e..05e58a6 100644
--- a/include/git2/index.h
+++ b/include/git2/index.h
@@ -77,7 +77,12 @@ typedef struct git_index_entry {
 #define GIT_IDXENTRY_VALID     (0x8000)
 #define GIT_IDXENTRY_STAGESHIFT 12
 
-#define GIT_IDXENTRY_STAGE(E) (((E)->flags & GIT_IDXENTRY_STAGEMASK) >> GIT_IDXENTRY_STAGESHIFT)
+#define GIT_IDXENTRY_STAGE(E) \
+	(((E)->flags & GIT_IDXENTRY_STAGEMASK) >> GIT_IDXENTRY_STAGESHIFT)
+
+#define GIT_IDXENTRY_STAGE_SET(E,S) do { \
+	(E)->flags = ((E)->flags & ~GIT_IDXENTRY_STAGEMASK) | \
+		(((S) & 0x03) << GIT_IDXENTRY_STAGESHIFT); } while (0)
 
 /**
  * Bitmasks for on-disk fields of `git_index_entry`'s `flags_extended`
@@ -327,12 +332,14 @@ GIT_EXTERN(size_t) git_index_entrycount(const git_index *index);
 
 /**
  * Clear the contents (all the entries) of an index object.
- * This clears the index object in memory; changes must be manually
- * written to disk for them to take effect.
+ *
+ * This clears the index object in memory; changes must be explicitly
+ * written to disk for them to take effect persistently.
  *
  * @param index an existing index object
+ * @return 0 on success, error code < 0 on failure
  */
-GIT_EXTERN(void) git_index_clear(git_index *index);
+GIT_EXTERN(int) git_index_clear(git_index *index);
 
 /**
  * Get a pointer to one of the entries in the index
@@ -568,8 +575,7 @@ GIT_EXTERN(int) git_index_update_all(
  * @param at_pos the address to which the position of the index entry is written (optional)
  * @param index an existing index object
  * @param path path to search
- * @return a zero-based position in the index if found;
- * GIT_ENOTFOUND otherwise
+ * @return a zero-based position in the index if found; GIT_ENOTFOUND otherwise
  */
 GIT_EXTERN(int) git_index_find(size_t *at_pos, git_index *index, const char *path);
 
@@ -613,6 +619,7 @@ GIT_EXTERN(int) git_index_conflict_add(
  * @param their_out Pointer to store the their entry
  * @param index an existing index object
  * @param path path to search
+ * @return 0 or an error code
  */
 GIT_EXTERN(int) git_index_conflict_get(
 	const git_index_entry **ancestor_out,
@@ -625,16 +632,18 @@ GIT_EXTERN(int) git_index_conflict_get(
  * Removes the index entries that represent a conflict of a single file.
  *
  * @param index an existing index object
- * @param path to search
+ * @param path path to remove conflicts for
+ * @return 0 or an error code
  */
 GIT_EXTERN(int) git_index_conflict_remove(git_index *index, const char *path);
 
 /**
- * Remove all conflicts in the index (entries with a stage greater than 0.)
+ * Remove all conflicts in the index (entries with a stage greater than 0).
  *
  * @param index an existing index object
+ * @return 0 or an error code
  */
-GIT_EXTERN(void) git_index_conflict_cleanup(git_index *index);
+GIT_EXTERN(int) git_index_conflict_cleanup(git_index *index);
 
 /**
  * Determine if the index contains entries representing file conflicts.
@@ -644,9 +653,12 @@ GIT_EXTERN(void) git_index_conflict_cleanup(git_index *index);
 GIT_EXTERN(int) git_index_has_conflicts(const git_index *index);
 
 /**
- * Create an iterator for the conflicts in the index.  You may not modify the
- * index while iterating, the results are undefined.
+ * Create an iterator for the conflicts in the index.
+ *
+ * The index must not be modified while iterating; the results are undefined.
  *
+ * @param iterator_out The newly created conflict iterator
+ * @param index The index to scan
  * @return 0 or an error code
  */
 GIT_EXTERN(int) git_index_conflict_iterator_new(
diff --git a/include/git2/sys/diff.h b/include/git2/sys/diff.h
new file mode 100644
index 0000000..bc6cdf3
--- /dev/null
+++ b/include/git2/sys/diff.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_sys_git_diff_h__
+#define INCLUDE_sys_git_diff_h__
+
+#include "git2/common.h"
+#include "git2/types.h"
+#include "git2/oid.h"
+
+/**
+ * @file git2/sys/diff.h
+ * @brief Low-level Git diff utilities
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Diff print callback that writes to a git_buf.
+ *
+ * This function is provided not for you to call it directly, but instead
+ * so you can use it as a function pointer to the `git_diff_print` or
+ * `git_patch_print` APIs.  When using those APIs, you specify a callback
+ * to actually handle the diff and/or patch data.
+ *
+ * Use this callback to easily write that data to a `git_buf` buffer.  You
+ * must pass a `git_buf *` value as the payload to the `git_diff_print`
+ * and/or `git_patch_print` function.  The data will be appended to the
+ * buffer (after any existing content).
+ */
+GIT_EXTERN(int) git_diff_print_callback__to_buf(
+	const git_diff_delta *delta,
+	const git_diff_hunk *hunk,
+	const git_diff_line *line,
+	void *payload); /*< payload must be a `git_buf *` */
+
+/**
+ * Diff print callback that writes to stdio FILE handle.
+ *
+ * This function is provided not for you to call it directly, but instead
+ * so you can use it as a function pointer to the `git_diff_print` or
+ * `git_patch_print` APIs.  When using those APIs, you specify a callback
+ * to actually handle the diff and/or patch data.
+ *
+ * Use this callback to easily write that data to a stdio FILE handle.  You
+ * must pass a `FILE *` value (such as `stdout` or `stderr` or the return
+ * value from `fopen()`) as the payload to the `git_diff_print`
+ * and/or `git_patch_print` function.  If you pass NULL, this will write
+ * data to `stdout`.
+ */
+GIT_EXTERN(int) git_diff_print_callback__to_file_handle(
+	const git_diff_delta *delta,
+	const git_diff_hunk *hunk,
+	const git_diff_line *line,
+	void *payload); /*< payload must be a `FILE *` */
+
+/** @} */
+GIT_END_DECL
+#endif
diff --git a/src/attr.c b/src/attr.c
index d8a171d..6228743 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -2,7 +2,7 @@
 #include "repository.h"
 #include "sysdir.h"
 #include "config.h"
-#include "attr.h"
+#include "attr_file.h"
 #include "ignore.h"
 #include "git2/oid.h"
 #include <ctype.h>
@@ -33,6 +33,7 @@ static int collect_attr_files(
 	const char *path,
 	git_vector *files);
 
+static void release_attr_files(git_vector *files);
 
 int git_attr_get(
 	const char **value,
@@ -59,6 +60,7 @@ int git_attr_get(
 	if ((error = collect_attr_files(repo, flags, pathname, &files)) < 0)
 		goto cleanup;
 
+	memset(&attr, 0, sizeof(attr));
 	attr.name = name;
 	attr.name_hash = git_attr_file__name_hash(name);
 
@@ -76,7 +78,7 @@ int git_attr_get(
 	}
 
 cleanup:
-	git_vector_free(&files);
+	release_attr_files(&files);
 	git_attr_path__free(&path);
 
 	return error;
@@ -152,7 +154,7 @@ int git_attr_get_many(
 	}
 
 cleanup:
-	git_vector_free(&files);
+	release_attr_files(&files);
 	git_attr_path__free(&path);
 	git__free(info);
 
@@ -181,12 +183,10 @@ int git_attr_foreach(
 	if (git_attr_path__init(&path, pathname, git_repository_workdir(repo)) < 0)
 		return -1;
 
-	if ((error = collect_attr_files(repo, flags, pathname, &files)) < 0)
+	if ((error = collect_attr_files(repo, flags, pathname, &files)) < 0 ||
+		(error = git_strmap_alloc(&seen)) < 0)
 		goto cleanup;
 
-	seen = git_strmap_alloc();
-	GITERR_CHECK_ALLOC(seen);
-
 	git_vector_foreach(&files, i, file) {
 
 		git_attr_file__foreach_matching_rule(file, &path, j, rule) {
@@ -211,13 +211,12 @@ int git_attr_foreach(
 
 cleanup:
 	git_strmap_free(seen);
-	git_vector_free(&files);
+	release_attr_files(&files);
 	git_attr_path__free(&path);
 
 	return error;
 }
 
-
 int git_attr_add_macro(
 	git_repository *repo,
 	const char *name,
@@ -252,237 +251,6 @@ int git_attr_add_macro(
 	return error;
 }
 
-bool git_attr_cache__is_cached(
-	git_repository *repo, git_attr_file_source source, const char *path)
-{
-	git_buf cache_key = GIT_BUF_INIT;
-	git_strmap *files = git_repository_attr_cache(repo)->files;
-	const char *workdir = git_repository_workdir(repo);
-	bool rval;
-
-	if (workdir && git__prefixcmp(path, workdir) == 0)
-		path += strlen(workdir);
-	if (git_buf_printf(&cache_key, "%d#%s", (int)source, path) < 0)
-		return false;
-
-	rval = git_strmap_exists(files, git_buf_cstr(&cache_key));
-
-	git_buf_free(&cache_key);
-
-	return rval;
-}
-
-static int load_attr_file(
-	const char **data,
-	git_futils_filestamp *stamp,
-	const char *filename)
-{
-	int error;
-	git_buf content = GIT_BUF_INIT;
-
-	error = git_futils_filestamp_check(stamp, filename);
-	if (error < 0)
-		return error;
-
-	/* if error == 0, then file is up to date. By returning GIT_ENOTFOUND,
-	 * we tell the caller not to reparse this file...
-	 */
-	if (!error)
-		return GIT_ENOTFOUND;
-
-	error = git_futils_readbuffer(&content, filename);
-	if (error < 0) {
-		/* convert error into ENOTFOUND so failed permissions / invalid
-		 * file type don't actually stop the operation in progress.
-		 */
-		return GIT_ENOTFOUND;
-
-		/* TODO: once warnings are available, issue a warning callback */
-	}
-
-	*data = git_buf_detach(&content);
-
-	return 0;
-}
-
-static int load_attr_blob_from_index(
-	const char **content,
-	git_blob **blob,
-	git_repository *repo,
-	const git_oid *old_oid,
-	const char *relfile)
-{
-	int error;
-	size_t pos;
-	git_index *index;
-	const git_index_entry *entry;
-
-	if ((error = git_repository_index__weakptr(&index, repo)) < 0 ||
-		(error = git_index_find(&pos, index, relfile)) < 0)
-		return error;
-
-	entry = git_index_get_byindex(index, pos);
-
-	if (old_oid && git_oid__cmp(old_oid, &entry->id) == 0)
-		return GIT_ENOTFOUND;
-
-	if ((error = git_blob_lookup(blob, repo, &entry->id)) < 0)
-		return error;
-
-	*content = git_blob_rawcontent(*blob);
-	return 0;
-}
-
-static int load_attr_from_cache(
-	git_attr_file **file,
-	git_attr_cache *cache,
-	git_attr_file_source source,
-	const char *relative_path)
-{
-	git_buf  cache_key = GIT_BUF_INIT;
-	khiter_t cache_pos;
-
-	*file = NULL;
-
-	if (!cache || !cache->files)
-		return 0;
-
-	if (git_buf_printf(&cache_key, "%d#%s", (int)source, relative_path) < 0)
-		return -1;
-
-	cache_pos = git_strmap_lookup_index(cache->files, cache_key.ptr);
-
-	git_buf_free(&cache_key);
-
-	if (git_strmap_valid_index(cache->files, cache_pos))
-		*file = git_strmap_value_at(cache->files, cache_pos);
-
-	return 0;
-}
-
-int git_attr_cache__internal_file(
-	git_repository *repo,
-	const char *filename,
-	git_attr_file **file)
-{
-	int error = 0;
-	git_attr_cache *cache = git_repository_attr_cache(repo);
-	khiter_t cache_pos = git_strmap_lookup_index(cache->files, filename);
-
-	if (git_strmap_valid_index(cache->files, cache_pos)) {
-		*file = git_strmap_value_at(cache->files, cache_pos);
-		return 0;
-	}
-
-	if (git_attr_file__new(file, 0, filename, &cache->pool) < 0)
-		return -1;
-
-	git_strmap_insert(cache->files, (*file)->key + 2, *file, error);
-	if (error > 0)
-		error = 0;
-
-	return error;
-}
-
-int git_attr_cache__push_file(
-	git_repository *repo,
-	const char *base,
-	const char *filename,
-	git_attr_file_source source,
-	git_attr_file_parser parse,
-	void* parsedata,
-	git_vector *stack)
-{
-	int error = 0;
-	git_buf path = GIT_BUF_INIT;
-	const char *workdir = git_repository_workdir(repo);
-	const char *relfile, *content = NULL;
-	git_attr_cache *cache = git_repository_attr_cache(repo);
-	git_attr_file *file = NULL;
-	git_blob *blob = NULL;
-	git_futils_filestamp stamp;
-
-	assert(filename && stack);
-
-	/* join base and path as needed */
-	if (base != NULL && git_path_root(filename) < 0) {
-		if (git_buf_joinpath(&path, base, filename) < 0)
-			return -1;
-		filename = path.ptr;
-	}
-
-	relfile = filename;
-	if (workdir && git__prefixcmp(relfile, workdir) == 0)
-		relfile += strlen(workdir);
-
-	/* check cache */
-	if (load_attr_from_cache(&file, cache, source, relfile) < 0)
-		return -1;
-
-	/* if not in cache, load data, parse, and cache */
-
-	if (source == GIT_ATTR_FILE_FROM_FILE) {
-		git_futils_filestamp_set(
-			&stamp, file ? &file->cache_data.stamp : NULL);
-
-		error = load_attr_file(&content, &stamp, filename);
-	} else {
-		error = load_attr_blob_from_index(&content, &blob,
-			repo, file ? &file->cache_data.oid : NULL, relfile);
-	}
-
-	if (error) {
-		/* not finding a file is not an error for this function */
-		if (error == GIT_ENOTFOUND) {
-			giterr_clear();
-			error = 0;
-		}
-		goto finish;
-	}
-
-	/* if we got here, we have to parse and/or reparse the file */
-	if (file)
-		git_attr_file__clear_rules(file);
-	else {
-		error = git_attr_file__new(&file, source, relfile, &cache->pool);
-		if (error < 0)
-			goto finish;
-	}
-
-	if (parse && (error = parse(repo, parsedata, content, file)) < 0)
-		goto finish;
-
-	git_strmap_insert(cache->files, file->key, file, error); //-V595
-	if (error > 0)
-		error = 0;
-
-	/* remember "cache buster" file signature */
-	if (blob)
-		git_oid_cpy(&file->cache_data.oid, git_object_id((git_object *)blob));
-	else
-		git_futils_filestamp_set(&file->cache_data.stamp, &stamp);
-
-finish:
-	/* push file onto vector if we found one*/
-	if (!error && file != NULL)
-		error = git_vector_insert(stack, file);
-
-	if (error != 0)
-		git_attr_file__free(file);
-
-	if (blob)
-		git_blob_free(blob);
-	else
-		git__free((void *)content);
-
-	git_buf_free(&path);
-
-	return error;
-}
-
-#define push_attr_file(R,S,B,F) \
-	git_attr_cache__push_file((R),(B),(F),GIT_ATTR_FILE_FROM_FILE,git_attr_file__parse_buffer,NULL,(S))
-
 typedef struct {
 	git_repository *repo;
 	uint32_t flags;
@@ -491,7 +259,7 @@ typedef struct {
 	git_vector *files;
 } attr_walk_up_info;
 
-int git_attr_cache__decide_sources(
+static int attr_decide_sources(
 	uint32_t flags, bool has_wd, bool has_index, git_attr_file_source *srcs)
 {
 	int count = 0;
@@ -499,42 +267,76 @@ int git_attr_cache__decide_sources(
 	switch (flags & 0x03) {
 	case GIT_ATTR_CHECK_FILE_THEN_INDEX:
 		if (has_wd)
-			srcs[count++] = GIT_ATTR_FILE_FROM_FILE;
+			srcs[count++] = GIT_ATTR_FILE__FROM_FILE;
 		if (has_index)
-			srcs[count++] = GIT_ATTR_FILE_FROM_INDEX;
+			srcs[count++] = GIT_ATTR_FILE__FROM_INDEX;
 		break;
 	case GIT_ATTR_CHECK_INDEX_THEN_FILE:
 		if (has_index)
-			srcs[count++] = GIT_ATTR_FILE_FROM_INDEX;
+			srcs[count++] = GIT_ATTR_FILE__FROM_INDEX;
 		if (has_wd)
-			srcs[count++] = GIT_ATTR_FILE_FROM_FILE;
+			srcs[count++] = GIT_ATTR_FILE__FROM_FILE;
 		break;
 	case GIT_ATTR_CHECK_INDEX_ONLY:
 		if (has_index)
-			srcs[count++] = GIT_ATTR_FILE_FROM_INDEX;
+			srcs[count++] = GIT_ATTR_FILE__FROM_INDEX;
 		break;
 	}
 
 	return count;
 }
 
+static int push_attr_file(
+	git_repository *repo,
+	git_vector *list,
+	git_attr_file_source source,
+	const char *base,
+	const char *filename)
+{
+	int error = 0;
+	git_attr_file *file = NULL;
+
+	error = git_attr_cache__get(
+		&file, repo, source, base, filename, git_attr_file__parse_buffer);
+	if (error < 0)
+		return error;
+
+	if (file != NULL) {
+		if ((error = git_vector_insert(list, file)) < 0)
+			git_attr_file__free(file);
+	}
+
+	return error;
+}
+
 static int push_one_attr(void *ref, git_buf *path)
 {
 	int error = 0, n_src, i;
 	attr_walk_up_info *info = (attr_walk_up_info *)ref;
 	git_attr_file_source src[2];
 
-	n_src = git_attr_cache__decide_sources(
+	n_src = attr_decide_sources(
 		info->flags, info->workdir != NULL, info->index != NULL, src);
 
 	for (i = 0; !error && i < n_src; ++i)
-		error = git_attr_cache__push_file(
-			info->repo, path->ptr, GIT_ATTR_FILE, src[i],
-			git_attr_file__parse_buffer, NULL, info->files);
+		error = push_attr_file(
+			info->repo, info->files, src[i], path->ptr, GIT_ATTR_FILE);
 
 	return error;
 }
 
+static void release_attr_files(git_vector *files)
+{
+	size_t i;
+	git_attr_file *file;
+
+	git_vector_foreach(files, i, file) {
+		git_attr_file__free(file);
+		files->contents[i] = NULL;
+	}
+	git_vector_free(files);
+}
+
 static int collect_attr_files(
 	git_repository *repo,
 	uint32_t flags,
@@ -546,9 +348,8 @@ static int collect_attr_files(
 	const char *workdir = git_repository_workdir(repo);
 	attr_walk_up_info info = { NULL };
 
-	if (git_attr_cache__init(repo) < 0 ||
-		git_vector_init(files, 4, NULL) < 0)
-		return -1;
+	if ((error = git_attr_cache__init(repo)) < 0)
+		return error;
 
 	/* Resolve path in a non-bare repo */
 	if (workdir != NULL)
@@ -566,7 +367,8 @@ static int collect_attr_files(
 	 */
 
 	error = push_attr_file(
-		repo, files, git_repository_path(repo), GIT_ATTR_FILE_INREPO);
+		repo, files, GIT_ATTR_FILE__FROM_FILE,
+		git_repository_path(repo), GIT_ATTR_FILE_INREPO);
 	if (error < 0)
 		goto cleanup;
 
@@ -583,7 +385,8 @@ static int collect_attr_files(
 
 	if (git_repository_attr_cache(repo)->cfg_attr_file != NULL) {
 		error = push_attr_file(
-			repo, files, NULL, git_repository_attr_cache(repo)->cfg_attr_file);
+			repo, files, GIT_ATTR_FILE__FROM_FILE,
+			NULL, git_repository_attr_cache(repo)->cfg_attr_file);
 		if (error < 0)
 			goto cleanup;
 	}
@@ -591,7 +394,8 @@ static int collect_attr_files(
 	if ((flags & GIT_ATTR_CHECK_NO_SYSTEM) == 0) {
 		error = git_sysdir_find_system_file(&dir, GIT_ATTR_FILE_SYSTEM);
 		if (!error)
-			error = push_attr_file(repo, files, NULL, dir.ptr);
+			error = push_attr_file(
+				repo, files, GIT_ATTR_FILE__FROM_FILE, NULL, dir.ptr);
 		else if (error == GIT_ENOTFOUND) {
 			giterr_clear();
 			error = 0;
@@ -600,153 +404,8 @@ static int collect_attr_files(
 
  cleanup:
 	if (error < 0)
-		git_vector_free(files);
+		release_attr_files(files);
 	git_buf_free(&dir);
 
 	return error;
 }
-
-static int attr_cache__lookup_path(
-	char **out, git_config *cfg, const char *key, const char *fallback)
-{
-	git_buf buf = GIT_BUF_INIT;
-	int error;
-	const git_config_entry *entry = NULL;
-
-	*out = NULL;
-
-	if ((error = git_config__lookup_entry(&entry, cfg, key, false)) < 0)
-		return error;
-
-	if (entry) {
-		const char *cfgval = entry->value;
-
-		/* expand leading ~/ as needed */
-		if (cfgval && cfgval[0] == '~' && cfgval[1] == '/' &&
-			!git_sysdir_find_global_file(&buf, &cfgval[2]))
-			*out = git_buf_detach(&buf);
-		else if (cfgval)
-			*out = git__strdup(cfgval);
-
-	}
-	else if (!git_sysdir_find_xdg_file(&buf, fallback))
-		*out = git_buf_detach(&buf);
-
-	git_buf_free(&buf);
-
-	return error;
-}
-
-int git_attr_cache__init(git_repository *repo)
-{
-	int ret;
-	git_attr_cache *cache = git_repository_attr_cache(repo);
-	git_config *cfg;
-
-	if (cache->initialized)
-		return 0;
-
-	/* cache config settings for attributes and ignores */
-	if (git_repository_config__weakptr(&cfg, repo) < 0)
-		return -1;
-
-	ret = attr_cache__lookup_path(
-		&cache->cfg_attr_file, cfg, GIT_ATTR_CONFIG, GIT_ATTR_FILE_XDG);
-	if (ret < 0)
-		return ret;
-
-	ret = attr_cache__lookup_path(
-		&cache->cfg_excl_file, cfg, GIT_IGNORE_CONFIG, GIT_IGNORE_FILE_XDG);
-	if (ret < 0)
-		return ret;
-
-	/* allocate hashtable for attribute and ignore file contents */
-	if (cache->files == NULL) {
-		cache->files = git_strmap_alloc();
-		GITERR_CHECK_ALLOC(cache->files);
-	}
-
-	/* allocate hashtable for attribute macros */
-	if (cache->macros == NULL) {
-		cache->macros = git_strmap_alloc();
-		GITERR_CHECK_ALLOC(cache->macros);
-	}
-
-	/* allocate string pool */
-	if (git_pool_init(&cache->pool, 1, 0) < 0)
-		return -1;
-
-	cache->initialized = 1;
-
-	/* insert default macros */
-	return git_attr_add_macro(repo, "binary", "-diff -crlf -text");
-}
-
-void git_attr_cache_flush(
-	git_repository *repo)
-{
-	git_attr_cache *cache;
-
-	if (!repo)
-		return;
-
-	cache = git_repository_attr_cache(repo);
-
-	if (cache->files != NULL) {
-		git_attr_file *file;
-
-		git_strmap_foreach_value(cache->files, file, {
-			git_attr_file__free(file);
-		});
-
-		git_strmap_free(cache->files);
-	}
-
-	if (cache->macros != NULL) {
-		git_attr_rule *rule;
-
-		git_strmap_foreach_value(cache->macros, rule, {
-			git_attr_rule__free(rule);
-		});
-
-		git_strmap_free(cache->macros);
-	}
-
-	git_pool_clear(&cache->pool);
-
-	git__free(cache->cfg_attr_file);
-	cache->cfg_attr_file = NULL;
-
-	git__free(cache->cfg_excl_file);
-	cache->cfg_excl_file = NULL;
-
-	cache->initialized = 0;
-}
-
-int git_attr_cache__insert_macro(git_repository *repo, git_attr_rule *macro)
-{
-	git_strmap *macros = git_repository_attr_cache(repo)->macros;
-	int error;
-
-	/* TODO: generate warning log if (macro->assigns.length == 0) */
-	if (macro->assigns.length == 0)
-		return 0;
-
-	git_strmap_insert(macros, macro->match.pattern, macro, error);
-	return (error < 0) ? -1 : 0;
-}
-
-git_attr_rule *git_attr_cache__lookup_macro(
-	git_repository *repo, const char *name)
-{
-	git_strmap *macros = git_repository_attr_cache(repo)->macros;
-	khiter_t pos;
-
-	pos = git_strmap_lookup_index(macros, name);
-
-	if (!git_strmap_valid_index(macros, pos))
-		return NULL;
-
-	return (git_attr_rule *)git_strmap_value_at(macros, pos);
-}
-
diff --git a/src/attr.h b/src/attr.h
index 19c979b..f9f216d 100644
--- a/src/attr.h
+++ b/src/attr.h
@@ -8,38 +8,6 @@
 #define INCLUDE_attr_h__
 
 #include "attr_file.h"
-
-#define GIT_ATTR_CONFIG       "core.attributesfile"
-#define GIT_IGNORE_CONFIG     "core.excludesfile"
-
-typedef int (*git_attr_file_parser)(
-	git_repository *, void *, const char *, git_attr_file *);
-
-extern int git_attr_cache__insert_macro(
-	git_repository *repo, git_attr_rule *macro);
-
-extern git_attr_rule *git_attr_cache__lookup_macro(
-	git_repository *repo, const char *name);
-
-extern int git_attr_cache__push_file(
-	git_repository *repo,
-	const char *base,
-	const char *filename,
-	git_attr_file_source source,
-	git_attr_file_parser parse,
-	void *parsedata, /* passed through to parse function */
-	git_vector *stack);
-
-extern int git_attr_cache__internal_file(
-	git_repository *repo,
-	const char *key,
-	git_attr_file **file_ptr);
-
-/* returns true if path is in cache */
-extern bool git_attr_cache__is_cached(
-	git_repository *repo, git_attr_file_source source, const char *path);
-
-extern int git_attr_cache__decide_sources(
-	uint32_t flags, bool has_wd, bool has_index, git_attr_file_source *srcs);
+#include "attrcache.h"
 
 #endif
diff --git a/src/attr_file.c b/src/attr_file.c
index ea92336..65bbf78 100644
--- a/src/attr_file.c
+++ b/src/attr_file.c
@@ -1,85 +1,239 @@
 #include "common.h"
 #include "repository.h"
 #include "filebuf.h"
-#include "attr.h"
+#include "attr_file.h"
+#include "attrcache.h"
 #include "git2/blob.h"
 #include "git2/tree.h"
+#include "index.h"
 #include <ctype.h>
 
-static int sort_by_hash_and_name(const void *a_raw, const void *b_raw);
-static void git_attr_rule__clear(git_attr_rule *rule);
-static bool parse_optimized_patterns(
-	git_attr_fnmatch *spec,
-	git_pool *pool,
-	const char *pattern);
+static void attr_file_free(git_attr_file *file)
+{
+	bool unlock = !git_mutex_lock(&file->lock);
+	git_attr_file__clear_rules(file, false);
+	git_pool_clear(&file->pool);
+	if (unlock)
+		git_mutex_unlock(&file->lock);
+	git_mutex_free(&file->lock);
+
+	git__memzero(file, sizeof(*file));
+	git__free(file);
+}
 
 int git_attr_file__new(
-	git_attr_file **attrs_ptr,
-	git_attr_file_source from,
-	const char *path,
-	git_pool *pool)
+	git_attr_file **out,
+	git_attr_file_entry *entry,
+	git_attr_file_source source)
 {
-	git_attr_file *attrs = NULL;
-
-	attrs = git__calloc(1, sizeof(git_attr_file));
+	git_attr_file *attrs = git__calloc(1, sizeof(git_attr_file));
 	GITERR_CHECK_ALLOC(attrs);
 
-	if (pool)
-		attrs->pool = pool;
-	else {
-		attrs->pool = git__calloc(1, sizeof(git_pool));
-		if (!attrs->pool || git_pool_init(attrs->pool, 1, 0) < 0)
-			goto fail;
-		attrs->pool_is_allocated = true;
+	if (git_mutex_init(&attrs->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to initialize lock");
+		git__free(attrs);
+		return -1;
 	}
 
-	if (path) {
-		size_t len = strlen(path);
+	if (git_pool_init(&attrs->pool, 1, 0) < 0) {
+		attr_file_free(attrs);
+		return -1;
+	}
+
+	GIT_REFCOUNT_INC(attrs);
+	attrs->entry  = entry;
+	attrs->source = source;
+	*out = attrs;
+	return 0;
+}
 
-		attrs->key = git_pool_malloc(attrs->pool, (uint32_t)len + 3);
-		GITERR_CHECK_ALLOC(attrs->key);
+int git_attr_file__clear_rules(git_attr_file *file, bool need_lock)
+{
+	unsigned int i;
+	git_attr_rule *rule;
 
-		attrs->key[0] = '0' + (char)from;
-		attrs->key[1] = '#';
-		memcpy(&attrs->key[2], path, len);
-		attrs->key[len + 2] = '\0';
+	if (need_lock && git_mutex_lock(&file->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock attribute file");
+		return -1;
 	}
 
-	if (git_vector_init(&attrs->rules, 4, NULL) < 0)
-		goto fail;
+	git_vector_foreach(&file->rules, i, rule)
+		git_attr_rule__free(rule);
+	git_vector_free(&file->rules);
+
+	if (need_lock)
+		git_mutex_unlock(&file->lock);
 
-	*attrs_ptr = attrs;
 	return 0;
+}
 
-fail:
-	git_attr_file__free(attrs);
-	attrs_ptr = NULL;
-	return -1;
+void git_attr_file__free(git_attr_file *file)
+{
+	if (!file)
+		return;
+	GIT_REFCOUNT_DEC(file, attr_file_free);
 }
 
-int git_attr_file__parse_buffer(
-	git_repository *repo, void *parsedata, const char *buffer, git_attr_file *attrs)
+static int attr_file_oid_from_index(
+	git_oid *oid, git_repository *repo, const char *path)
+{
+	int error;
+	git_index *idx;
+	size_t pos;
+	const git_index_entry *entry;
+
+	if ((error = git_repository_index__weakptr(&idx, repo)) < 0 ||
+		(error = git_index__find_pos(&pos, idx, path, 0, 0)) < 0)
+		return error;
+
+	if (!(entry = git_index_get_byindex(idx, pos)))
+		return GIT_ENOTFOUND;
+
+	*oid = entry->id;
+	return 0;
+}
+
+int git_attr_file__load(
+	git_attr_file **out,
+	git_repository *repo,
+	git_attr_file_entry *entry,
+	git_attr_file_source source,
+	git_attr_file_parser parser)
 {
 	int error = 0;
-	const char *scan = NULL, *context = NULL;
-	git_attr_rule *rule = NULL;
+	git_blob *blob = NULL;
+	git_buf content = GIT_BUF_INIT;
+	const char *data = NULL;
+	git_attr_file *file;
+	struct stat st;
+
+	*out = NULL;
+
+	switch (source) {
+	case GIT_ATTR_FILE__IN_MEMORY:
+		/* in-memory attribute file doesn't need data */
+		break;
+	case GIT_ATTR_FILE__FROM_INDEX: {
+		git_oid id;
+
+		if ((error = attr_file_oid_from_index(&id, repo, entry->path)) < 0 ||
+			(error = git_blob_lookup(&blob, repo, &id)) < 0)
+			return error;
+
+		data = git_blob_rawcontent(blob);
+		break;
+	}
+	case GIT_ATTR_FILE__FROM_FILE: {
+		int fd;
+
+		if (p_stat(entry->fullpath, &st) < 0)
+			return git_path_set_error(errno, entry->fullpath, "stat");
+		if (S_ISDIR(st.st_mode))
+			return GIT_ENOTFOUND;
+
+		/* For open or read errors, return ENOTFOUND to skip item */
+		/* TODO: issue warning when warning API is available */
+
+		if ((fd = git_futils_open_ro(entry->fullpath)) < 0)
+			return GIT_ENOTFOUND;
+
+		error = git_futils_readbuffer_fd(&content, fd, (size_t)st.st_size);
+		p_close(fd);
 
-	GIT_UNUSED(parsedata);
+		if (error < 0)
+			return GIT_ENOTFOUND;
 
-	assert(buffer && attrs);
+		data = content.ptr;
+		break;
+	}
+	default:
+		giterr_set(GITERR_INVALID, "Unknown file source %d", source);
+		return -1;
+	}
 
-	scan = buffer;
+	if ((error = git_attr_file__new(&file, entry, source)) < 0)
+		goto cleanup;
+
+	if (parser && (error = parser(repo, file, data)) < 0) {
+		git_attr_file__free(file);
+		goto cleanup;
+	}
+
+	/* write cache breaker */
+	if (source == GIT_ATTR_FILE__FROM_INDEX)
+		git_oid_cpy(&file->cache_data.oid, git_blob_id(blob));
+	else if (source == GIT_ATTR_FILE__FROM_FILE)
+		git_futils_filestamp_set_from_stat(&file->cache_data.stamp, &st);
+	/* else always cacheable */
+
+	*out = file;
+
+cleanup:
+	git_blob_free(blob);
+	git_buf_free(&content);
+
+	return error;
+}
+
+int git_attr_file__out_of_date(git_repository *repo, git_attr_file *file)
+{
+	if (!file)
+		return 1;
+
+	switch (file->source) {
+	case GIT_ATTR_FILE__IN_MEMORY:
+		return 0;
+
+	case GIT_ATTR_FILE__FROM_FILE:
+		return git_futils_filestamp_check(
+			&file->cache_data.stamp, file->entry->fullpath);
+
+	case GIT_ATTR_FILE__FROM_INDEX: {
+		int error;
+		git_oid id;
+
+		if ((error = attr_file_oid_from_index(
+				&id, repo, file->entry->path)) < 0)
+			return error;
+
+		return (git_oid__cmp(&file->cache_data.oid, &id) != 0);
+	}
+
+	default:
+		giterr_set(GITERR_INVALID, "Invalid file type %d", file->source);
+		return -1;
+	}
+}
+
+static int sort_by_hash_and_name(const void *a_raw, const void *b_raw);
+static void git_attr_rule__clear(git_attr_rule *rule);
+static bool parse_optimized_patterns(
+	git_attr_fnmatch *spec,
+	git_pool *pool,
+	const char *pattern);
+
+int git_attr_file__parse_buffer(
+	git_repository *repo, git_attr_file *attrs, const char *data)
+{
+	int error = 0;
+	const char *scan = data, *context = NULL;
+	git_attr_rule *rule = NULL;
 
 	/* if subdir file path, convert context for file paths */
-	if (attrs->key &&
-		git_path_root(attrs->key + 2) < 0 &&
-		git__suffixcmp(attrs->key, "/" GIT_ATTR_FILE) == 0)
-		context = attrs->key + 2;
+	if (attrs->entry &&
+		git_path_root(attrs->entry->path) < 0 &&
+		!git__suffixcmp(attrs->entry->path, "/" GIT_ATTR_FILE))
+		context = attrs->entry->path;
+
+	if (git_mutex_lock(&attrs->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock attribute file");
+		return -1;
+	}
 
 	while (!error && *scan) {
 		/* allocate rule if needed */
 		if (!rule) {
-			if (!(rule = git__calloc(1, sizeof(git_attr_rule)))) {
+			if (!(rule = git__calloc(1, sizeof(*rule)))) {
 				error = -1;
 				break;
 			}
@@ -89,9 +243,9 @@ int git_attr_file__parse_buffer(
 
 		/* parse the next "pattern attr attr attr" line */
 		if (!(error = git_attr_fnmatch__parse(
-				&rule->match, attrs->pool, context, &scan)) &&
+				&rule->match, &attrs->pool, context, &scan)) &&
 			!(error = git_attr_assignment__parse(
-				repo, attrs->pool, &rule->assigns, &scan)))
+				repo, &attrs->pool, &rule->assigns, &scan)))
 		{
 			if (rule->match.flags & GIT_ATTR_FNMATCH_MACRO)
 				/* should generate error/warning if this is coming from any
@@ -112,62 +266,12 @@ int git_attr_file__parse_buffer(
 		}
 	}
 
+	git_mutex_unlock(&attrs->lock);
 	git_attr_rule__free(rule);
 
 	return error;
 }
 
-int git_attr_file__new_and_load(
-	git_attr_file **attrs_ptr,
-	const char *path)
-{
-	int error;
-	git_buf content = GIT_BUF_INIT;
-
-	if ((error = git_attr_file__new(attrs_ptr, 0, path, NULL)) < 0)
-		return error;
-
-	if (!(error = git_futils_readbuffer(&content, path)))
-		error = git_attr_file__parse_buffer(
-			NULL, NULL, git_buf_cstr(&content), *attrs_ptr);
-
-	git_buf_free(&content);
-
-	if (error) {
-		git_attr_file__free(*attrs_ptr);
-		*attrs_ptr = NULL;
-	}
-
-	return error;
-}
-
-void git_attr_file__clear_rules(git_attr_file *file)
-{
-	unsigned int i;
-	git_attr_rule *rule;
-
-	git_vector_foreach(&file->rules, i, rule)
-		git_attr_rule__free(rule);
-
-	git_vector_free(&file->rules);
-}
-
-void git_attr_file__free(git_attr_file *file)
-{
-	if (!file)
-		return;
-
-	git_attr_file__clear_rules(file);
-
-	if (file->pool_is_allocated) {
-		git_pool_clear(file->pool);
-		git__free(file->pool);
-	}
-	file->pool = NULL;
-
-	git__free(file);
-}
-
 uint32_t git_attr_file__name_hash(const char *name)
 {
 	uint32_t h = 5381;
@@ -178,7 +282,6 @@ uint32_t git_attr_file__name_hash(const char *name)
 	return h;
 }
 
-
 int git_attr_file__lookup_one(
 	git_attr_file *file,
 	const git_attr_path *path,
@@ -207,25 +310,63 @@ int git_attr_file__lookup_one(
 	return 0;
 }
 
+int git_attr_file__load_standalone(git_attr_file **out, const char *path)
+{
+	int error;
+	git_attr_file *file;
+	git_buf content = GIT_BUF_INIT;
+
+	error = git_attr_file__new(&file, NULL, GIT_ATTR_FILE__FROM_FILE);
+	if (error < 0)
+		return error;
+
+	error = git_attr_cache__alloc_file_entry(
+		&file->entry, NULL, path, &file->pool);
+	if (error < 0) {
+		git_attr_file__free(file);
+		return error;
+	}
+	/* because the cache entry is allocated from the file's own pool, we
+	 * don't have to free it - freeing file+pool will free cache entry, too.
+	 */
+
+	if (!(error = git_futils_readbuffer(&content, path))) {
+		error = git_attr_file__parse_buffer(NULL, file, content.ptr);
+		git_buf_free(&content);
+	}
+
+	if (error < 0)
+		git_attr_file__free(file);
+	else
+		*out = file;
+
+	return error;
+}
 
 bool git_attr_fnmatch__match(
 	git_attr_fnmatch *match,
 	const git_attr_path *path)
 {
-	int fnm;
-	int icase_flags = (match->flags & GIT_ATTR_FNMATCH_ICASE) ? FNM_CASEFOLD : 0;
+	const char *filename;
+	int flags = 0;
 
-	if (match->flags & GIT_ATTR_FNMATCH_DIRECTORY && !path->is_dir)
+	if ((match->flags & GIT_ATTR_FNMATCH_DIRECTORY) && !path->is_dir)
 		return false;
 
-	if (match->flags & GIT_ATTR_FNMATCH_FULLPATH)
-		fnm = p_fnmatch(match->pattern, path->path, FNM_PATHNAME | icase_flags);
-	else if (path->is_dir)
-		fnm = p_fnmatch(match->pattern, path->basename, FNM_LEADING_DIR | icase_flags);
-	else
-		fnm = p_fnmatch(match->pattern, path->basename, icase_flags);
+	if (match->flags & GIT_ATTR_FNMATCH_ICASE)
+		flags |= FNM_CASEFOLD;
 
-	return (fnm == FNM_NOMATCH) ? false : true;
+	if (match->flags & GIT_ATTR_FNMATCH_FULLPATH) {
+		filename = path->path;
+		flags |= FNM_PATHNAME;
+	} else {
+		filename = path->basename;
+
+		if (path->is_dir)
+			flags |= FNM_LEADING_DIR;
+	}
+
+	return (p_fnmatch(match->pattern, filename, flags) != FNM_NOMATCH);
 }
 
 bool git_attr_rule__match(
@@ -240,7 +381,6 @@ bool git_attr_rule__match(
 	return matched;
 }
 
-
 git_attr_assignment *git_attr_rule__lookup_assignment(
 	git_attr_rule *rule, const char *name)
 {
@@ -339,7 +479,7 @@ void git_attr_path__free(git_attr_path *info)
 int git_attr_fnmatch__parse(
 	git_attr_fnmatch *spec,
 	git_pool *pool,
-	const char *source,
+	const char *context,
 	const char **base)
 {
 	const char *pattern, *scan;
@@ -407,21 +547,21 @@ int git_attr_fnmatch__parse(
 	}
 
 	if ((spec->flags & GIT_ATTR_FNMATCH_FULLPATH) != 0 &&
-		source != NULL && git_path_root(pattern) < 0)
+		context != NULL && git_path_root(pattern) < 0)
 	{
-        /* use context path minus the trailing filename */
-        char *slash = strrchr(source, '/');
-        size_t sourcelen = slash ? slash - source + 1 : 0;
+		/* use context path minus the trailing filename */
+		char *slash = strrchr(context, '/');
+		size_t contextlen = slash ? slash - context + 1 : 0;
 
 		/* given an unrooted fullpath match from a file inside a repo,
 		 * prefix the pattern with the relative directory of the source file
 		 */
 		spec->pattern = git_pool_malloc(
-			pool, (uint32_t)(sourcelen + spec->length + 1));
+			pool, (uint32_t)(contextlen + spec->length + 1));
 		if (spec->pattern) {
-			memcpy(spec->pattern, source, sourcelen);
-			memcpy(spec->pattern + sourcelen, pattern, spec->length);
-			spec->length += sourcelen;
+			memcpy(spec->pattern, context, contextlen);
+			memcpy(spec->pattern + contextlen, pattern, spec->length);
+			spec->length += contextlen;
 			spec->pattern[spec->length] = '\0';
 		}
 	} else {
@@ -434,6 +574,7 @@ int git_attr_fnmatch__parse(
 	} else {
 		/* strip '\' that might have be used for internal whitespace */
 		spec->length = git__unescape(spec->pattern);
+		/* TODO: convert remaining '\' into '/' for POSIX ??? */
 	}
 
 	return 0;
diff --git a/src/attr_file.h b/src/attr_file.h
index 3bc7c6c..c906be4 100644
--- a/src/attr_file.h
+++ b/src/attr_file.h
@@ -35,6 +35,14 @@
 	(GIT_ATTR_FNMATCH_ALLOWSPACE | \
 	 GIT_ATTR_FNMATCH_ALLOWNEG | GIT_ATTR_FNMATCH_ALLOWMACRO)
 
+typedef enum {
+	GIT_ATTR_FILE__IN_MEMORY  = 0,
+	GIT_ATTR_FILE__FROM_FILE  = 1,
+	GIT_ATTR_FILE__FROM_INDEX = 2,
+
+	GIT_ATTR_FILE_NUM_SOURCES = 3
+} git_attr_file_source;
+
 extern const char *git_attr__true;
 extern const char *git_attr__false;
 extern const char *git_attr__unset;
@@ -63,17 +71,32 @@ typedef struct {
 	const char *value;
 } git_attr_assignment;
 
+typedef struct git_attr_file_entry git_attr_file_entry;
+
 typedef struct {
-	char *key;				/* cache "source#path" this was loaded from */
-	git_vector rules;		/* vector of <rule*> or <fnmatch*> */
-	git_pool *pool;
-	bool pool_is_allocated;
+	git_refcount rc;
+	git_mutex lock;
+	git_attr_file_entry *entry;
+	git_attr_file_source source;
+	git_vector rules;			/* vector of <rule*> or <fnmatch*> */
+	git_pool pool;
 	union {
 		git_oid oid;
 		git_futils_filestamp stamp;
 	} cache_data;
 } git_attr_file;
 
+struct git_attr_file_entry {
+	git_attr_file *file[GIT_ATTR_FILE_NUM_SOURCES];
+	const char *path; /* points into fullpath */
+	char fullpath[GIT_FLEX_ARRAY];
+};
+
+typedef int (*git_attr_file_parser)(
+	git_repository *repo,
+	git_attr_file *file,
+	const char *data);
+
 typedef struct {
 	git_buf  full;
 	char    *path;
@@ -81,29 +104,37 @@ typedef struct {
 	int      is_dir;
 } git_attr_path;
 
-typedef enum {
-	GIT_ATTR_FILE_FROM_FILE = 0,
-	GIT_ATTR_FILE_FROM_INDEX = 1
-} git_attr_file_source;
-
 /*
  * git_attr_file API
  */
 
-extern int git_attr_file__new(
-	git_attr_file **attrs_ptr, git_attr_file_source src, const char *path, git_pool *pool);
+int git_attr_file__new(
+	git_attr_file **out,
+	git_attr_file_entry *entry,
+	git_attr_file_source source);
+
+void git_attr_file__free(git_attr_file *file);
+
+int git_attr_file__load(
+	git_attr_file **out,
+	git_repository *repo,
+	git_attr_file_entry *ce,
+	git_attr_file_source source,
+	git_attr_file_parser parser);
 
-extern int git_attr_file__new_and_load(
-	git_attr_file **attrs_ptr, const char *path);
+int git_attr_file__load_standalone(
+	git_attr_file **out, const char *path);
 
-extern void git_attr_file__free(git_attr_file *file);
+int git_attr_file__out_of_date(
+	git_repository *repo, git_attr_file *file);
 
-extern void git_attr_file__clear_rules(git_attr_file *file);
+int git_attr_file__parse_buffer(
+	git_repository *repo, git_attr_file *attrs, const char *data);
 
-extern int git_attr_file__parse_buffer(
-	git_repository *repo, void *parsedata, const char *buf, git_attr_file *file);
+int git_attr_file__clear_rules(
+	git_attr_file *file, bool need_lock);
 
-extern int git_attr_file__lookup_one(
+int git_attr_file__lookup_one(
 	git_attr_file *file,
 	const git_attr_path *path,
 	const char *attr,
@@ -114,7 +145,7 @@ extern int git_attr_file__lookup_one(
 	git_vector_rforeach(&(file)->rules, (iter), (rule)) \
 		if (git_attr_rule__match((rule), (path)))
 
-extern uint32_t git_attr_file__name_hash(const char *name);
+uint32_t git_attr_file__name_hash(const char *name);
 
 
 /*
diff --git a/src/attrcache.c b/src/attrcache.c
new file mode 100644
index 0000000..88b68eb
--- /dev/null
+++ b/src/attrcache.c
@@ -0,0 +1,448 @@
+#include "common.h"
+#include "repository.h"
+#include "attr_file.h"
+#include "config.h"
+#include "sysdir.h"
+#include "ignore.h"
+
+GIT__USE_STRMAP;
+
+GIT_INLINE(int) attr_cache_lock(git_attr_cache *cache)
+{
+	GIT_UNUSED(cache); /* avoid warning if threading is off */
+
+	if (git_mutex_lock(&cache->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to get attr cache lock");
+		return -1;
+	}
+	return 0;
+}
+
+GIT_INLINE(void) attr_cache_unlock(git_attr_cache *cache)
+{
+	GIT_UNUSED(cache); /* avoid warning if threading is off */
+	git_mutex_unlock(&cache->lock);
+}
+
+GIT_INLINE(git_attr_file_entry *) attr_cache_lookup_entry(
+	git_attr_cache *cache, const char *path)
+{
+	khiter_t pos = git_strmap_lookup_index(cache->files, path);
+
+	if (git_strmap_valid_index(cache->files, pos))
+		return git_strmap_value_at(cache->files, pos);
+	else
+		return NULL;
+}
+
+int git_attr_cache__alloc_file_entry(
+	git_attr_file_entry **out,
+	const char *base,
+	const char *path,
+	git_pool *pool)
+{
+	size_t baselen = 0, pathlen = strlen(path);
+	size_t cachesize = sizeof(git_attr_file_entry) + pathlen + 1;
+	git_attr_file_entry *ce;
+
+	if (base != NULL && git_path_root(path) < 0) {
+		baselen = strlen(base);
+		cachesize += baselen;
+
+		if (baselen && base[baselen - 1] != '/')
+			cachesize++;
+	}
+
+	ce = git_pool_mallocz(pool, cachesize);
+	GITERR_CHECK_ALLOC(ce);
+
+	if (baselen) {
+		memcpy(ce->fullpath, base, baselen);
+
+		if (base[baselen - 1] != '/')
+			ce->fullpath[baselen++] = '/';
+	}
+	memcpy(&ce->fullpath[baselen], path, pathlen);
+
+	ce->path = &ce->fullpath[baselen];
+	*out = ce;
+
+	return 0;
+}
+
+/* call with attrcache locked */
+static int attr_cache_make_entry(
+	git_attr_file_entry **out, git_repository *repo, const char *path)
+{
+	int error = 0;
+	git_attr_cache *cache = git_repository_attr_cache(repo);
+	git_attr_file_entry *entry = NULL;
+
+	error = git_attr_cache__alloc_file_entry(
+		&entry, git_repository_workdir(repo), path, &cache->pool);
+
+	if (!error) {
+		git_strmap_insert(cache->files, entry->path, entry, error);
+		if (error > 0)
+			error = 0;
+	}
+
+	*out = entry;
+	return error;
+}
+
+/* insert entry or replace existing if we raced with another thread */
+static int attr_cache_upsert(git_attr_cache *cache, git_attr_file *file)
+{
+	git_attr_file_entry *entry;
+	git_attr_file *old;
+
+	if (attr_cache_lock(cache) < 0)
+		return -1;
+
+	entry = attr_cache_lookup_entry(cache, file->entry->path);
+
+	GIT_REFCOUNT_OWN(file, entry);
+	GIT_REFCOUNT_INC(file);
+
+	old = git__compare_and_swap(
+		&entry->file[file->source], entry->file[file->source], file);
+
+	if (old) {
+		GIT_REFCOUNT_OWN(old, NULL);
+		git_attr_file__free(old);
+	}
+
+	attr_cache_unlock(cache);
+	return 0;
+}
+
+static int attr_cache_remove(git_attr_cache *cache, git_attr_file *file)
+{
+	int error = 0;
+	git_attr_file_entry *entry;
+
+	if (!file)
+		return 0;
+	if ((error = attr_cache_lock(cache)) < 0)
+		return error;
+
+	if ((entry = attr_cache_lookup_entry(cache, file->entry->path)) != NULL)
+		file = git__compare_and_swap(&entry->file[file->source], file, NULL);
+
+	attr_cache_unlock(cache);
+
+	if (file) {
+		GIT_REFCOUNT_OWN(file, NULL);
+		git_attr_file__free(file);
+	}
+
+	return error;
+}
+
+/* Look up cache entry and file.
+ * - If entry is not present, create it while the cache is locked.
+ * - If file is present, increment refcount before returning it, so the
+ *   cache can be unlocked and it won't go away.
+ */
+static int attr_cache_lookup(
+	git_attr_file **out_file,
+	git_attr_file_entry **out_entry,
+	git_repository *repo,
+	git_attr_file_source source,
+	const char *base,
+	const char *filename)
+{
+	int error = 0;
+	git_buf path = GIT_BUF_INIT;
+	const char *wd = git_repository_workdir(repo), *relfile;
+	git_attr_cache *cache = git_repository_attr_cache(repo);
+	git_attr_file_entry *entry = NULL;
+	git_attr_file *file = NULL;
+
+	/* join base and path as needed */
+	if (base != NULL && git_path_root(filename) < 0) {
+		if (git_buf_joinpath(&path, base, filename) < 0)
+			return -1;
+		filename = path.ptr;
+	}
+
+	relfile = filename;
+	if (wd && !git__prefixcmp(relfile, wd))
+		relfile += strlen(wd);
+
+	/* check cache for existing entry */
+	if ((error = attr_cache_lock(cache)) < 0)
+		goto cleanup;
+
+	entry = attr_cache_lookup_entry(cache, relfile);
+	if (!entry) {
+		if ((error = attr_cache_make_entry(&entry, repo, relfile)) < 0)
+			goto cleanup;
+	} else if (entry->file[source] != NULL) {
+		file = entry->file[source];
+		GIT_REFCOUNT_INC(file);
+	}
+
+	attr_cache_unlock(cache);
+
+cleanup:
+	*out_file  = file;
+	*out_entry = entry;
+
+	git_buf_free(&path);
+	return error;
+}
+
+int git_attr_cache__get(
+	git_attr_file **out,
+	git_repository *repo,
+	git_attr_file_source source,
+	const char *base,
+	const char *filename,
+	git_attr_file_parser parser)
+{
+	int error = 0;
+	git_attr_cache *cache = git_repository_attr_cache(repo);
+	git_attr_file_entry *entry = NULL;
+	git_attr_file *file = NULL, *updated = NULL;
+
+	if ((error = attr_cache_lookup(
+			&file, &entry, repo, source, base, filename)) < 0)
+		return error;
+
+	/* load file if we don't have one or if existing one is out of date */
+	if (!file || (error = git_attr_file__out_of_date(repo, file)) > 0)
+		error = git_attr_file__load(&updated, repo, entry, source, parser);
+
+	/* if we loaded the file, insert into and/or update cache */
+	if (updated) {
+		if ((error = attr_cache_upsert(cache, updated)) < 0)
+			git_attr_file__free(updated);
+		else {
+			git_attr_file__free(file); /* offset incref from lookup */
+			file = updated;
+		}
+	}
+
+	/* if file could not be loaded */
+	if (error < 0) {
+		/* remove existing entry */
+		if (file) {
+			git_attr_file__free(file); /* offset incref from lookup */
+			attr_cache_remove(cache, file);
+			file = NULL;
+		}
+		/* no error if file simply doesn't exist */
+		if (error == GIT_ENOTFOUND) {
+			giterr_clear();
+			error = 0;
+		}
+	}
+
+	*out = file;
+	return error;
+}
+
+bool git_attr_cache__is_cached(
+	git_repository *repo,
+	git_attr_file_source source,
+	const char *filename)
+{
+	git_attr_cache *cache = git_repository_attr_cache(repo);
+	git_strmap *files;
+	khiter_t pos;
+	git_attr_file_entry *entry;
+
+	if (!(cache = git_repository_attr_cache(repo)) ||
+		!(files = cache->files))
+		return false;
+
+	pos = git_strmap_lookup_index(files, filename);
+	if (!git_strmap_valid_index(files, pos))
+		return false;
+
+	entry = git_strmap_value_at(files, pos);
+
+	return entry && (entry->file[source] != NULL);
+}
+
+
+static int attr_cache__lookup_path(
+	char **out, git_config *cfg, const char *key, const char *fallback)
+{
+	git_buf buf = GIT_BUF_INIT;
+	int error;
+	const git_config_entry *entry = NULL;
+
+	*out = NULL;
+
+	if ((error = git_config__lookup_entry(&entry, cfg, key, false)) < 0)
+		return error;
+
+	if (entry) {
+		const char *cfgval = entry->value;
+
+		/* expand leading ~/ as needed */
+		if (cfgval && cfgval[0] == '~' && cfgval[1] == '/' &&
+			!git_sysdir_find_global_file(&buf, &cfgval[2]))
+			*out = git_buf_detach(&buf);
+		else if (cfgval)
+			*out = git__strdup(cfgval);
+	}
+	else if (!git_sysdir_find_xdg_file(&buf, fallback))
+		*out = git_buf_detach(&buf);
+
+	git_buf_free(&buf);
+
+	return error;
+}
+
+static void attr_cache__free(git_attr_cache *cache)
+{
+	bool unlock;
+
+	if (!cache)
+		return;
+
+	unlock = (git_mutex_lock(&cache->lock) == 0);
+
+	if (cache->files != NULL) {
+		git_attr_file_entry *entry;
+		git_attr_file *file;
+		int i;
+
+		git_strmap_foreach_value(cache->files, entry, {
+			for (i = 0; i < GIT_ATTR_FILE_NUM_SOURCES; ++i) {
+				if ((file = git__swap(entry->file[i], NULL)) != NULL) {
+					GIT_REFCOUNT_OWN(file, NULL);
+					git_attr_file__free(file);
+				}
+			}
+		});
+		git_strmap_free(cache->files);
+	}
+
+	if (cache->macros != NULL) {
+		git_attr_rule *rule;
+
+		git_strmap_foreach_value(cache->macros, rule, {
+			git_attr_rule__free(rule);
+		});
+		git_strmap_free(cache->macros);
+	}
+
+	git_pool_clear(&cache->pool);
+
+	git__free(cache->cfg_attr_file);
+	cache->cfg_attr_file = NULL;
+
+	git__free(cache->cfg_excl_file);
+	cache->cfg_excl_file = NULL;
+
+	if (unlock)
+		git_mutex_unlock(&cache->lock);
+	git_mutex_free(&cache->lock);
+
+	git__free(cache);
+}
+
+int git_attr_cache__do_init(git_repository *repo)
+{
+	int ret = 0;
+	git_attr_cache *cache = git_repository_attr_cache(repo);
+	git_config *cfg;
+
+	if (cache)
+		return 0;
+
+	if ((ret = git_repository_config__weakptr(&cfg, repo)) < 0)
+		return ret;
+
+	cache = git__calloc(1, sizeof(git_attr_cache));
+	GITERR_CHECK_ALLOC(cache);
+
+	/* set up lock */
+	if (git_mutex_init(&cache->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to initialize lock for attr cache");
+		git__free(cache);
+		return -1;
+	}
+
+	/* cache config settings for attributes and ignores */
+	ret = attr_cache__lookup_path(
+		&cache->cfg_attr_file, cfg, GIT_ATTR_CONFIG, GIT_ATTR_FILE_XDG);
+	if (ret < 0)
+		goto cancel;
+
+	ret = attr_cache__lookup_path(
+		&cache->cfg_excl_file, cfg, GIT_IGNORE_CONFIG, GIT_IGNORE_FILE_XDG);
+	if (ret < 0)
+		goto cancel;
+
+	/* allocate hashtable for attribute and ignore file contents,
+	 * hashtable for attribute macros, and string pool
+	 */
+	if ((ret = git_strmap_alloc(&cache->files)) < 0 ||
+		(ret = git_strmap_alloc(&cache->macros)) < 0 ||
+		(ret = git_pool_init(&cache->pool, 1, 0)) < 0)
+		goto cancel;
+
+	cache = git__compare_and_swap(&repo->attrcache, NULL, cache);
+	if (cache)
+		goto cancel; /* raced with another thread, free this but no error */
+
+	/* insert default macros */
+	return git_attr_add_macro(repo, "binary", "-diff -crlf -text");
+
+cancel:
+	attr_cache__free(cache);
+	return ret;
+}
+
+void git_attr_cache_flush(git_repository *repo)
+{
+	git_attr_cache *cache;
+
+	/* this could be done less expensively, but for now, we'll just free
+	 * the entire attrcache and let the next use reinitialize it...
+	 */
+	if (repo && (cache = git__swap(repo->attrcache, NULL)) != NULL)
+		attr_cache__free(cache);
+}
+
+int git_attr_cache__insert_macro(git_repository *repo, git_attr_rule *macro)
+{
+	git_attr_cache *cache = git_repository_attr_cache(repo);
+	git_strmap *macros = cache->macros;
+	int error;
+
+	/* TODO: generate warning log if (macro->assigns.length == 0) */
+	if (macro->assigns.length == 0)
+		return 0;
+
+	if (git_mutex_lock(&cache->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to get attr cache lock");
+		error = -1;
+	} else {
+		git_strmap_insert(macros, macro->match.pattern, macro, error);
+		git_mutex_unlock(&cache->lock);
+	}
+
+	return (error < 0) ? -1 : 0;
+}
+
+git_attr_rule *git_attr_cache__lookup_macro(
+	git_repository *repo, const char *name)
+{
+	git_strmap *macros = git_repository_attr_cache(repo)->macros;
+	khiter_t pos;
+
+	pos = git_strmap_lookup_index(macros, name);
+
+	if (!git_strmap_valid_index(macros, pos))
+		return NULL;
+
+	return (git_attr_rule *)git_strmap_value_at(macros, pos);
+}
+
diff --git a/src/attrcache.h b/src/attrcache.h
index 077633b..be0a22f 100644
--- a/src/attrcache.h
+++ b/src/attrcache.h
@@ -7,18 +7,50 @@
 #ifndef INCLUDE_attrcache_h__
 #define INCLUDE_attrcache_h__
 
-#include "pool.h"
+#include "attr_file.h"
 #include "strmap.h"
 
+#define GIT_ATTR_CONFIG       "core.attributesfile"
+#define GIT_IGNORE_CONFIG     "core.excludesfile"
+
 typedef struct {
-	int initialized;
-	git_pool pool;
-	git_strmap *files;	 /* hash path to git_attr_file of rules */
-	git_strmap *macros;	 /* hash name to vector<git_attr_assignment> */
 	char *cfg_attr_file; /* cached value of core.attributesfile */
 	char *cfg_excl_file; /* cached value of core.excludesfile */
+	git_strmap *files;	 /* hash path to git_attr_cache_entry records */
+	git_strmap *macros;	 /* hash name to vector<git_attr_assignment> */
+	git_mutex lock;
+	git_pool  pool;
 } git_attr_cache;
 
-extern int git_attr_cache__init(git_repository *repo);
+extern int git_attr_cache__do_init(git_repository *repo);
+
+#define git_attr_cache__init(REPO) \
+	(git_repository_attr_cache(REPO) ? 0 : git_attr_cache__do_init(REPO))
+
+/* get file - loading and reload as needed */
+extern int git_attr_cache__get(
+	git_attr_file **file,
+	git_repository *repo,
+	git_attr_file_source source,
+	const char *base,
+	const char *filename,
+	git_attr_file_parser parser);
+
+extern bool git_attr_cache__is_cached(
+	git_repository *repo,
+	git_attr_file_source source,
+	const char *path);
+
+extern int git_attr_cache__alloc_file_entry(
+	git_attr_file_entry **out,
+	const char *base,
+	const char *path,
+	git_pool *pool);
+
+extern int git_attr_cache__insert_macro(
+	git_repository *repo, git_attr_rule *macro);
+
+extern git_attr_rule *git_attr_cache__lookup_macro(
+	git_repository *repo, const char *name);
 
 #endif
diff --git a/src/checkout.c b/src/checkout.c
index 141fc13..0b38522 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -277,19 +277,23 @@ static int checkout_action_wd_only(
 
 	/* check if item is tracked in the index but not in the checkout diff */
 	if (data->index != NULL) {
+		size_t pos;
+
+		error = git_index__find_pos(
+			&pos, data->index, wd->path, 0, GIT_INDEX_STAGE_ANY);
+
 		if (wd->mode != GIT_FILEMODE_TREE) {
-			if (!(error = git_index_find(NULL, data->index, wd->path))) {
+			if (!error) { /* found by git_index__find_pos call */
 				notify = GIT_CHECKOUT_NOTIFY_DIRTY;
 				remove = ((data->strategy & GIT_CHECKOUT_FORCE) != 0);
 			} else if (error != GIT_ENOTFOUND)
 				return error;
 			else
-				giterr_clear();
+				error = 0; /* git_index__find_pos does not set error msg */
 		} else {
 			/* for tree entries, we have to see if there are any index
 			 * entries that are contained inside that tree
 			 */
-			size_t pos = git_index__prefix_position(data->index, wd->path);
 			const git_index_entry *e = git_index_get_byindex(data->index, pos);
 
 			if (e != NULL && data->diff->pfxcomp(e->path, wd->path) == 0) {
@@ -653,10 +657,13 @@ static int checkout_conflictdata_cmp(const void *a, const void *b)
 	return diff;
 }
 
-int checkout_conflictdata_empty(const git_vector *conflicts, size_t idx)
+int checkout_conflictdata_empty(
+	const git_vector *conflicts, size_t idx, void *payload)
 {
 	checkout_conflictdata *conflict;
 
+	GIT_UNUSED(payload);
+
 	if ((conflict = git_vector_get(conflicts, idx)) == NULL)
 		return -1;
 
@@ -954,7 +961,8 @@ static int checkout_conflicts_coalesce_renames(
 			ancestor_conflict->one_to_two = 1;
 	}
 
-	git_vector_remove_matching(&data->conflicts, checkout_conflictdata_empty);
+	git_vector_remove_matching(
+		&data->conflicts, checkout_conflictdata_empty, NULL);
 
 done:
 	return error;
diff --git a/src/common.h b/src/common.h
index d389cf8..9c8bdc1 100644
--- a/src/common.h
+++ b/src/common.h
@@ -46,6 +46,7 @@
 # include <unistd.h>
 # ifdef GIT_THREADS
 #	include <pthread.h>
+#	include <sched.h>
 # endif
 #define GIT_STDLIB_CALL
 
diff --git a/src/config_file.c b/src/config_file.c
index aedf2cb..bb26aa8 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -180,11 +180,15 @@ static int config_open(git_config_backend *cfg, git_config_level_t level)
 
 	b->level = level;
 
-	b->values = git_strmap_alloc();
-	GITERR_CHECK_ALLOC(b->values);
+	if ((res = git_strmap_alloc(&b->values)) < 0)
+		return res;
 
 	git_array_init(b->readers);
 	reader = git_array_alloc(b->readers);
+	if (!reader) {
+		git_strmap_free(b->values);
+		return -1;
+	}
 	memset(reader, 0, sizeof(struct reader));
 
 	reader->file_path = git__strdup(b->file_path);
@@ -205,6 +209,7 @@ static int config_open(git_config_backend *cfg, git_config_level_t level)
 
 	reader = git_array_get(b->readers, 0);
 	git_buf_free(&reader->buffer);
+
 	return res;
 }
 
@@ -218,8 +223,10 @@ static int config_refresh(git_config_backend *cfg)
 
 	for (i = 0; i < git_array_size(b->readers); i++) {
 		reader = git_array_get(b->readers, i);
+
 		res = git_futils_readbuffer_updated(
-			&reader->buffer, reader->file_path, &reader->file_mtime, &reader->file_size, &updated);
+			&reader->buffer, reader->file_path,
+			&reader->file_mtime, &reader->file_size, &updated);
 
 		if (res < 0)
 			return (res == GIT_ENOTFOUND) ? 0 : res;
@@ -233,10 +240,9 @@ static int config_refresh(git_config_backend *cfg)
 
 	/* need to reload - store old values and prep for reload */
 	old_values = b->values;
-	b->values = git_strmap_alloc();
-	GITERR_CHECK_ALLOC(b->values);
-
-	if ((res = config_parse(b, reader, b->level, 0)) < 0) {
+	if ((res = git_strmap_alloc(&b->values)) < 0) {
+		b->values = old_values;
+	} else if ((res = config_parse(b, reader, b->level, 0)) < 0) {
 		free_vars(b->values);
 		b->values = old_values;
 	} else {
diff --git a/src/diff.c b/src/diff.c
index cb05a5f..0d1aed4 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -318,6 +318,31 @@ static const char *diff_mnemonic_prefix(
 	return pfx;
 }
 
+static void diff_set_ignore_case(git_diff *diff, bool ignore_case)
+{
+	if (!ignore_case) {
+		diff->opts.flags &= ~GIT_DIFF_IGNORE_CASE;
+
+		diff->strcomp    = git__strcmp;
+		diff->strncomp   = git__strncmp;
+		diff->pfxcomp    = git__prefixcmp;
+		diff->entrycomp  = git_index_entry_cmp;
+
+		git_vector_set_cmp(&diff->deltas, git_diff_delta__cmp);
+	} else {
+		diff->opts.flags |= GIT_DIFF_IGNORE_CASE;
+
+		diff->strcomp    = git__strcasecmp;
+		diff->strncomp   = git__strncasecmp;
+		diff->pfxcomp    = git__prefixcmp_icase;
+		diff->entrycomp  = git_index_entry_icmp;
+
+		git_vector_set_cmp(&diff->deltas, git_diff_delta__casecmp);
+	}
+
+	git_vector_sort(&diff->deltas);
+}
+
 static git_diff *diff_list_alloc(
 	git_repository *repo,
 	git_iterator *old_iter,
@@ -344,24 +369,10 @@ static git_diff *diff_list_alloc(
 
 	/* Use case-insensitive compare if either iterator has
 	 * the ignore_case bit set */
-	if (!git_iterator_ignore_case(old_iter) &&
-		!git_iterator_ignore_case(new_iter)) {
-		diff->opts.flags &= ~GIT_DIFF_IGNORE_CASE;
-
-		diff->strcomp    = git__strcmp;
-		diff->strncomp   = git__strncmp;
-		diff->pfxcomp    = git__prefixcmp;
-		diff->entrycomp  = git_index_entry__cmp;
-	} else {
-		diff->opts.flags |= GIT_DIFF_IGNORE_CASE;
-
-		diff->strcomp    = git__strcasecmp;
-		diff->strncomp   = git__strncasecmp;
-		diff->pfxcomp    = git__prefixcmp_icase;
-		diff->entrycomp  = git_index_entry__cmp_icase;
-
-		git_vector_set_cmp(&diff->deltas, git_diff_delta__casecmp);
-	}
+	diff_set_ignore_case(
+		diff,
+		git_iterator_ignore_case(old_iter) ||
+		git_iterator_ignore_case(new_iter));
 
 	return diff;
 }
@@ -1183,39 +1194,25 @@ int git_diff_tree_to_index(
 	const git_diff_options *opts)
 {
 	int error = 0;
-	bool reset_index_ignore_case = false;
+	bool index_ignore_case = false;
 
 	assert(diff && repo);
 
 	if (!index && (error = diff_load_index(&index, repo)) < 0)
 		return error;
 
-	if (index->ignore_case) {
-		git_index__set_ignore_case(index, false);
-		reset_index_ignore_case = true;
-	}
+	index_ignore_case = index->ignore_case;
 
 	DIFF_FROM_ITERATORS(
-		git_iterator_for_tree(&a, old_tree, 0, pfx, pfx),
-		git_iterator_for_index(&b, index, 0, pfx, pfx)
+		git_iterator_for_tree(
+			&a, old_tree, GIT_ITERATOR_DONT_IGNORE_CASE, pfx, pfx),
+		git_iterator_for_index(
+			&b, index, GIT_ITERATOR_DONT_IGNORE_CASE, pfx, pfx)
 	);
 
-	if (reset_index_ignore_case) {
-		git_index__set_ignore_case(index, true);
-
-		if (!error) {
-			git_diff *d = *diff;
-
-			d->opts.flags |= GIT_DIFF_IGNORE_CASE;
-			d->strcomp    = git__strcasecmp;
-			d->strncomp   = git__strncasecmp;
-			d->pfxcomp    = git__prefixcmp_icase;
-			d->entrycomp  = git_index_entry__cmp_icase;
-
-			git_vector_set_cmp(&d->deltas, git_diff_delta__casecmp);
-			git_vector_sort(&d->deltas);
-		}
-	}
+	/* if index is in case-insensitive order, re-sort deltas to match */
+	if (!error && index_ignore_case)
+		diff_set_ignore_case(*diff, true);
 
 	return error;
 }
diff --git a/src/diff_driver.c b/src/diff_driver.c
index 4c9a0af..8136e0d 100644
--- a/src/diff_driver.c
+++ b/src/diff_driver.c
@@ -66,7 +66,7 @@ git_diff_driver_registry *git_diff_driver_registry_new()
 	if (!reg)
 		return NULL;
 
-	if ((reg->drivers = git_strmap_alloc()) == NULL) {
+	if (git_strmap_alloc(&reg->drivers) < 0) {
 		git_diff_driver_registry_free(reg);
 		return NULL;
 	}
diff --git a/src/diff_print.c b/src/diff_print.c
index 1a09bed..a7f7b6f 100644
--- a/src/diff_print.c
+++ b/src/diff_print.c
@@ -8,6 +8,7 @@
 #include "diff.h"
 #include "diff_patch.h"
 #include "fileops.h"
+#include "git2/sys/diff.h"
 
 typedef struct {
 	git_diff *diff;
@@ -435,7 +436,7 @@ int git_patch_print(
 	return error;
 }
 
-static int diff_print_to_buffer_cb(
+int git_diff_print_callback__to_buf(
 	const git_diff_delta *delta,
 	const git_diff_hunk *hunk,
 	const git_diff_line *line,
@@ -444,6 +445,11 @@ static int diff_print_to_buffer_cb(
 	git_buf *output = payload;
 	GIT_UNUSED(delta); GIT_UNUSED(hunk);
 
+	if (!output) {
+		giterr_set(GITERR_INVALID, "Buffer pointer must be provided");
+		return -1;
+	}
+
 	if (line->origin == GIT_DIFF_LINE_ADDITION ||
 		line->origin == GIT_DIFF_LINE_DELETION ||
 		line->origin == GIT_DIFF_LINE_CONTEXT)
@@ -452,10 +458,28 @@ static int diff_print_to_buffer_cb(
 	return git_buf_put(output, line->content, line->content_len);
 }
 
+int git_diff_print_callback__to_file_handle(
+	const git_diff_delta *delta,
+	const git_diff_hunk *hunk,
+	const git_diff_line *line,
+	void *payload)
+{
+	FILE *fp = payload ? payload : stdout;
+
+	GIT_UNUSED(delta); GIT_UNUSED(hunk);
+
+	if (line->origin == GIT_DIFF_LINE_CONTEXT ||
+		line->origin == GIT_DIFF_LINE_ADDITION ||
+		line->origin == GIT_DIFF_LINE_DELETION)
+		fputc(line->origin, fp);
+	fwrite(line->content, 1, line->content_len, fp);
+	return 0;
+}
+
 /* print a git_patch to a git_buf */
 int git_patch_to_buf(
 	git_buf *out,
 	git_patch *patch)
 {
-	return git_patch_print(patch, diff_print_to_buffer_cb, out);
+	return git_patch_print(patch, git_diff_print_callback__to_buf, out);
 }
diff --git a/src/fileops.c b/src/fileops.c
index 5709499..13b8f6a 100644
--- a/src/fileops.c
+++ b/src/fileops.c
@@ -132,6 +132,7 @@ int git_futils_readbuffer_fd(git_buf *buf, git_file fd, size_t len)
 
 	if (read_size != (ssize_t)len) {
 		giterr_set(GITERR_OS, "Failed to read descriptor");
+		git_buf_free(buf);
 		return -1;
 	}
 
@@ -804,10 +805,8 @@ int git_futils_filestamp_check(
 	if (stamp == NULL)
 		return 1;
 
-	if (p_stat(path, &st) < 0) {
-		giterr_set(GITERR_OS, "Could not stat '%s'", path);
+	if (p_stat(path, &st) < 0)
 		return GIT_ENOTFOUND;
-	}
 
 	if (stamp->mtime == (git_time_t)st.st_mtime &&
 		stamp->size  == (git_off_t)st.st_size   &&
@@ -831,3 +830,16 @@ void git_futils_filestamp_set(
 	else
 		memset(target, 0, sizeof(*target));
 }
+
+
+void git_futils_filestamp_set_from_stat(
+	git_futils_filestamp *stamp, struct stat *st)
+{
+	if (st) {
+		stamp->mtime = (git_time_t)st->st_mtime;
+		stamp->size  = (git_off_t)st->st_size;
+		stamp->ino   = (unsigned int)st->st_ino;
+	} else {
+		memset(stamp, 0, sizeof(*stamp));
+	}
+}
diff --git a/src/fileops.h b/src/fileops.h
index 6a65235..62227ab 100644
--- a/src/fileops.h
+++ b/src/fileops.h
@@ -292,13 +292,14 @@ typedef struct {
  * Compare stat information for file with reference info.
  *
  * This function updates the file stamp to current data for the given path
- * and returns 0 if the file is up-to-date relative to the prior setting or
- * 1 if the file has been changed.  (This also may return GIT_ENOTFOUND if
- * the file doesn't exist.)
+ * and returns 0 if the file is up-to-date relative to the prior setting,
+ * 1 if the file has been changed, or GIT_ENOTFOUND if the file doesn't
+ * exist.  This will not call giterr_set, so you must set the error if you
+ * plan to return an error.
  *
  * @param stamp File stamp to be checked
  * @param path Path to stat and check if changed
- * @return 0 if up-to-date, 1 if out-of-date, <0 on error
+ * @return 0 if up-to-date, 1 if out-of-date, GIT_ENOTFOUND if cannot stat
  */
 extern int git_futils_filestamp_check(
 	git_futils_filestamp *stamp, const char *path);
@@ -316,4 +317,10 @@ extern int git_futils_filestamp_check(
 extern void git_futils_filestamp_set(
 	git_futils_filestamp *tgt, const git_futils_filestamp *src);
 
+/**
+ * Set file stamp data from stat structure
+ */
+extern void git_futils_filestamp_set_from_stat(
+	git_futils_filestamp *stamp, struct stat *st);
+
 #endif /* INCLUDE_fileops_h__ */
diff --git a/src/global.c b/src/global.c
index c26b4b3..15baf1e 100644
--- a/src/global.c
+++ b/src/global.c
@@ -16,8 +16,9 @@ git_mutex git__mwindow_mutex;
 
 #define MAX_SHUTDOWN_CB 8
 
-git_global_shutdown_fn git__shutdown_callbacks[MAX_SHUTDOWN_CB];
-git_atomic git__n_shutdown_callbacks;
+static git_global_shutdown_fn git__shutdown_callbacks[MAX_SHUTDOWN_CB];
+static git_atomic git__n_shutdown_callbacks;
+static git_atomic git__n_inits;
 
 void git__on_shutdown(git_global_shutdown_fn callback)
 {
@@ -74,7 +75,6 @@ static void git__shutdown(void)
 
 static DWORD _tls_index;
 static DWORD _mutex = 0;
-static DWORD _n_inits = 0;
 
 static int synchronized_threads_init()
 {
@@ -101,7 +101,7 @@ int git_threads_init(void)
 	while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
 
 	/* Only do work on a 0 -> 1 transition of the refcount */
-	if (1 == ++_n_inits)
+	if (1 == git_atomic_inc(&git__n_inits))
 		error = synchronized_threads_init();
 
 	/* Exit the lock */
@@ -124,7 +124,7 @@ void git_threads_shutdown(void)
 	while (InterlockedCompareExchange(&_mutex, 1, 0)) { Sleep(0); }
 
 	/* Only do work on a 1 -> 0 transition of the refcount */
-	if (0 == --_n_inits)
+	if (0 == git_atomic_dec(&git__n_inits))
 		synchronized_threads_shutdown();
 
 	/* Exit the lock */
@@ -135,7 +135,7 @@ git_global_st *git__global_state(void)
 {
 	void *ptr;
 
-	assert(_n_inits);
+	assert(git_atomic_get(&git__n_inits) > 0);
 
 	if ((ptr = TlsGetValue(_tls_index)) != NULL)
 		return ptr;
@@ -153,7 +153,6 @@ git_global_st *git__global_state(void)
 
 static pthread_key_t _tls_key;
 static pthread_once_t _once_init = PTHREAD_ONCE_INIT;
-static git_atomic git__n_inits;
 int init_error = 0;
 
 static void cb__free_status(void *st)
@@ -204,7 +203,7 @@ git_global_st *git__global_state(void)
 {
 	void *ptr;
 
-	assert(git__n_inits.val);
+	assert(git_atomic_get(&git__n_inits) > 0);
 
 	if ((ptr = pthread_getspecific(_tls_key)) != NULL)
 		return ptr;
@@ -224,14 +223,15 @@ static git_global_st __state;
 
 int git_threads_init(void)
 {
-	/* noop */
+	git_atomic_inc(&git__n_inits);
 	return 0;
 }
 
 void git_threads_shutdown(void)
 {
 	/* Shut down any subsystems that have global state */
-	git__shutdown();
+	if (0 == git_atomic_dec(&git__n_inits))
+		git__shutdown();
 }
 
 git_global_st *git__global_state(void)
diff --git a/src/ignore.c b/src/ignore.c
index 5cf4fca..deae204 100644
--- a/src/ignore.c
+++ b/src/ignore.c
@@ -1,7 +1,7 @@
 #include "git2/ignore.h"
 #include "common.h"
 #include "ignore.h"
-#include "attr.h"
+#include "attrcache.h"
 #include "path.h"
 #include "config.h"
 
@@ -10,26 +10,26 @@
 #define GIT_IGNORE_DEFAULT_RULES ".\n..\n.git\n"
 
 static int parse_ignore_file(
-	git_repository *repo, void *parsedata, const char *buffer, git_attr_file *ignores)
+	git_repository *repo, git_attr_file *attrs, const char *data)
 {
 	int error = 0;
-	git_attr_fnmatch *match = NULL;
-	const char *scan = NULL, *context = NULL;
 	int ignore_case = false;
+	const char *scan = data, *context = NULL;
+	git_attr_fnmatch *match = NULL;
 
-	/* Prefer to have the caller pass in a git_ignores as the parsedata
-	 * object.  If they did not, then look up the value of ignore_case */
-	if (parsedata != NULL)
-		ignore_case = ((git_ignores *)parsedata)->ignore_case;
-	else if (git_repository__cvar(&ignore_case, repo, GIT_CVAR_IGNORECASE) < 0)
-		return error;
+	if (git_repository__cvar(&ignore_case, repo, GIT_CVAR_IGNORECASE) < 0)
+		giterr_clear();
 
-	if (ignores->key &&
-		git_path_root(ignores->key + 2) < 0 &&
-		git__suffixcmp(ignores->key, "/" GIT_IGNORE_FILE) == 0)
-		context = ignores->key + 2;
+	/* if subdir file path, convert context for file paths */
+	if (attrs->entry &&
+		git_path_root(attrs->entry->path) < 0 &&
+		!git__suffixcmp(attrs->entry->path, "/" GIT_IGNORE_FILE))
+		context = attrs->entry->path;
 
-	scan = buffer;
+	if (git_mutex_lock(&attrs->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock ignore file");
+		return -1;
+	}
 
 	while (!error && *scan) {
 		if (!match) {
@@ -40,7 +40,7 @@ static int parse_ignore_file(
 		match->flags = GIT_ATTR_FNMATCH_ALLOWSPACE | GIT_ATTR_FNMATCH_ALLOWNEG;
 
 		if (!(error = git_attr_fnmatch__parse(
-			match, ignores->pool, context, &scan)))
+			match, &attrs->pool, context, &scan)))
 		{
 			match->flags |= GIT_ATTR_FNMATCH_IGNORE;
 
@@ -48,7 +48,7 @@ static int parse_ignore_file(
 				match->flags |= GIT_ATTR_FNMATCH_ICASE;
 
 			scan = git__next_line(scan);
-			error = git_vector_insert(&ignores->rules, match);
+			error = git_vector_insert(&attrs->rules, match);
 		}
 
 		if (error != 0) {
@@ -62,33 +62,55 @@ static int parse_ignore_file(
 		}
 	}
 
+	git_mutex_unlock(&attrs->lock);
 	git__free(match);
 
 	return error;
 }
 
-#define push_ignore_file(R,IGN,S,B,F) \
-	git_attr_cache__push_file((R),(B),(F),GIT_ATTR_FILE_FROM_FILE,parse_ignore_file,(IGN),(S))
+static int push_ignore_file(
+	git_ignores *ignores,
+	git_vector *which_list,
+	const char *base,
+	const char *filename)
+{
+	int error = 0;
+	git_attr_file *file = NULL;
+
+	error = git_attr_cache__get(
+		&file, ignores->repo, GIT_ATTR_FILE__FROM_FILE,
+		base, filename, parse_ignore_file);
+	if (error < 0)
+		return error;
+
+	if (file != NULL) {
+		if ((error = git_vector_insert(which_list, file)) < 0)
+			git_attr_file__free(file);
+	}
+
+	return error;
+}
 
 static int push_one_ignore(void *payload, git_buf *path)
 {
 	git_ignores *ign = payload;
-
 	ign->depth++;
-
-	return push_ignore_file(
-		ign->repo, ign, &ign->ign_path, path->ptr, GIT_IGNORE_FILE);
+	return push_ignore_file(ign, &ign->ign_path, path->ptr, GIT_IGNORE_FILE);
 }
 
-static int get_internal_ignores(git_attr_file **ign, git_repository *repo)
+static int get_internal_ignores(git_attr_file **out, git_repository *repo)
 {
 	int error;
 
-	if (!(error = git_attr_cache__init(repo)))
-		error = git_attr_cache__internal_file(repo, GIT_IGNORE_INTERNAL, ign);
+	if ((error = git_attr_cache__init(repo)) < 0)
+		return error;
+
+	error = git_attr_cache__get(
+		out, repo, GIT_ATTR_FILE__IN_MEMORY, NULL, GIT_IGNORE_INTERNAL, NULL);
 
-	if (!error && !(*ign)->rules.length)
-		error = parse_ignore_file(repo, NULL, GIT_IGNORE_DEFAULT_RULES, *ign);
+	/* if internal rules list is empty, insert default rules */
+	if (!error && !(*out)->rules.length)
+		error = parse_ignore_file(repo, *out, GIT_IGNORE_DEFAULT_RULES);
 
 	return error;
 }
@@ -103,19 +125,15 @@ int git_ignore__for_path(
 
 	assert(ignores);
 
+	memset(ignores, 0, sizeof(*ignores));
 	ignores->repo = repo;
-	git_buf_init(&ignores->dir, 0);
-	ignores->ign_internal = NULL;
-	ignores->depth = 0;
 
 	/* Read the ignore_case flag */
 	if ((error = git_repository__cvar(
 			&ignores->ignore_case, repo, GIT_CVAR_IGNORECASE)) < 0)
 		goto cleanup;
 
-	if ((error = git_vector_init(&ignores->ign_path, 8, NULL)) < 0 ||
-		(error = git_vector_init(&ignores->ign_global, 2, NULL)) < 0 ||
-		(error = git_attr_cache__init(repo)) < 0)
+	if ((error = git_attr_cache__init(repo)) < 0)
 		goto cleanup;
 
 	/* given a unrooted path in a non-bare repo, resolve it */
@@ -127,8 +145,7 @@ int git_ignore__for_path(
 		goto cleanup;
 
 	/* set up internals */
-	error = get_internal_ignores(&ignores->ign_internal, repo);
-	if (error < 0)
+	if ((error = get_internal_ignores(&ignores->ign_internal, repo)) < 0)
 		goto cleanup;
 
 	/* load .gitignore up the path */
@@ -140,14 +157,16 @@ int git_ignore__for_path(
 	}
 
 	/* load .git/info/exclude */
-	error = push_ignore_file(repo, ignores, &ignores->ign_global,
+	error = push_ignore_file(
+		ignores, &ignores->ign_global,
 		git_repository_path(repo), GIT_IGNORE_FILE_INREPO);
 	if (error < 0)
 		goto cleanup;
 
 	/* load core.excludesfile */
 	if (git_repository_attr_cache(repo)->cfg_excl_file != NULL)
-		error = push_ignore_file(repo, ignores, &ignores->ign_global, NULL,
+		error = push_ignore_file(
+			ignores, &ignores->ign_global, NULL,
 			git_repository_attr_cache(repo)->cfg_excl_file);
 
 cleanup:
@@ -165,33 +184,34 @@ int git_ignore__push_dir(git_ignores *ign, const char *dir)
 	ign->depth++;
 
 	return push_ignore_file(
-		ign->repo, ign, &ign->ign_path, ign->dir.ptr, GIT_IGNORE_FILE);
+		ign, &ign->ign_path, ign->dir.ptr, GIT_IGNORE_FILE);
 }
 
 int git_ignore__pop_dir(git_ignores *ign)
 {
 	if (ign->ign_path.length > 0) {
 		git_attr_file *file = git_vector_last(&ign->ign_path);
-		const char *start, *end, *scan;
-		size_t keylen;
+		const char *start = file->entry->path, *end;
 
-		/* - ign->dir looks something like "a/b/" (or "a/b/c/d/")
-		 * - file->key looks something like "0#a/b/.gitignore
+		/* - ign->dir looks something like "/home/user/a/b/" (or "a/b/c/d/")
+		 * - file->path looks something like "a/b/.gitignore
 		 *
-		 * We are popping the last directory off ign->dir.  We also want to
-		 * remove the file from the vector if the directory part of the key
-		 * matches the ign->dir path.  We need to test if the "a/b" part of
+		 * We are popping the last directory off ign->dir.  We also want
+		 * to remove the file from the vector if the popped directory
+		 * matches the ignore path.  We need to test if the "a/b" part of
 		 * the file key matches the path we are about to pop.
 		 */
 
-		for (start = end = scan = &file->key[2]; *scan; ++scan)
-			if (*scan == '/')
-				end = scan; /* point 'end' to last '/' in key */
-		keylen = (end - start) + 1;
+		if ((end = strrchr(start, '/')) != NULL) {
+			size_t dirlen = (end - start) + 1;
 
-		if (ign->dir.size >= keylen &&
-			!memcmp(ign->dir.ptr + ign->dir.size - keylen, start, keylen))
-			git_vector_pop(&ign->ign_path);
+			if (ign->dir.size >= dirlen &&
+				!memcmp(ign->dir.ptr + ign->dir.size - dirlen, start, dirlen))
+			{
+				git_vector_pop(&ign->ign_path);
+				git_attr_file__free(file);
+			}
+		}
 	}
 
 	if (--ign->depth > 0) {
@@ -204,19 +224,33 @@ int git_ignore__pop_dir(git_ignores *ign)
 
 void git_ignore__free(git_ignores *ignores)
 {
-	/* don't need to free ignores->ign_internal since it is in cache */
+	unsigned int i;
+	git_attr_file *file;
+
+	git_attr_file__free(ignores->ign_internal);
+
+	git_vector_foreach(&ignores->ign_path, i, file) {
+		git_attr_file__free(file);
+		ignores->ign_path.contents[i] = NULL;
+	}
 	git_vector_free(&ignores->ign_path);
+
+	git_vector_foreach(&ignores->ign_global, i, file) {
+		git_attr_file__free(file);
+		ignores->ign_global.contents[i] = NULL;
+	}
 	git_vector_free(&ignores->ign_global);
+
 	git_buf_free(&ignores->dir);
 }
 
 static bool ignore_lookup_in_rules(
-	git_vector *rules, git_attr_path *path, int *ignored)
+	git_attr_file *file, git_attr_path *path, int *ignored)
 {
 	size_t j;
 	git_attr_fnmatch *match;
 
-	git_vector_rforeach(rules, j, match) {
+	git_vector_rforeach(&file->rules, j, match) {
 		if (git_attr_fnmatch__match(match, path)) {
 			*ignored = ((match->flags & GIT_ATTR_FNMATCH_NEGATIVE) == 0);
 			return true;
@@ -238,19 +272,18 @@ int git_ignore__lookup(
 		return -1;
 
 	/* first process builtins - success means path was found */
-	if (ignore_lookup_in_rules(
-			&ignores->ign_internal->rules, &path, ignored))
+	if (ignore_lookup_in_rules(ignores->ign_internal, &path, ignored))
 		goto cleanup;
 
 	/* next process files in the path */
 	git_vector_foreach(&ignores->ign_path, i, file) {
-		if (ignore_lookup_in_rules(&file->rules, &path, ignored))
+		if (ignore_lookup_in_rules(file, &path, ignored))
 			goto cleanup;
 	}
 
 	/* last process global ignores */
 	git_vector_foreach(&ignores->ign_global, i, file) {
-		if (ignore_lookup_in_rules(&file->rules, &path, ignored))
+		if (ignore_lookup_in_rules(file, &path, ignored))
 			goto cleanup;
 	}
 
@@ -261,32 +294,33 @@ cleanup:
 	return 0;
 }
 
-int git_ignore_add_rule(
-	git_repository *repo,
-	const char *rules)
+int git_ignore_add_rule(git_repository *repo, const char *rules)
 {
 	int error;
-	git_attr_file *ign_internal;
+	git_attr_file *ign_internal = NULL;
 
-	if (!(error = get_internal_ignores(&ign_internal, repo)))
-		error = parse_ignore_file(repo, NULL, rules, ign_internal);
+	if ((error = get_internal_ignores(&ign_internal, repo)) < 0)
+		return error;
+
+	error = parse_ignore_file(repo, ign_internal, rules);
+	git_attr_file__free(ign_internal);
 
 	return error;
 }
 
-int git_ignore_clear_internal_rules(
-	git_repository *repo)
+int git_ignore_clear_internal_rules(git_repository *repo)
 {
 	int error;
 	git_attr_file *ign_internal;
 
-	if (!(error = get_internal_ignores(&ign_internal, repo))) {
-		git_attr_file__clear_rules(ign_internal);
+	if ((error = get_internal_ignores(&ign_internal, repo)) < 0)
+		return error;
 
-		return parse_ignore_file(
-			repo, NULL, GIT_IGNORE_DEFAULT_RULES, ign_internal);
-	}
+	if (!(error = git_attr_file__clear_rules(ign_internal, true)))
+		error = parse_ignore_file(
+			repo, ign_internal, GIT_IGNORE_DEFAULT_RULES);
 
+	git_attr_file__free(ign_internal);
 	return error;
 }
 
@@ -331,19 +365,18 @@ int git_ignore_path_is_ignored(
 			break;
 
 		/* first process builtins - success means path was found */
-		if (ignore_lookup_in_rules(
-				&ignores.ign_internal->rules, &path, ignored))
+		if (ignore_lookup_in_rules(ignores.ign_internal, &path, ignored))
 			goto cleanup;
 
 		/* next process files in the path */
 		git_vector_foreach(&ignores.ign_path, i, file) {
-			if (ignore_lookup_in_rules(&file->rules, &path, ignored))
+			if (ignore_lookup_in_rules(file, &path, ignored))
 				goto cleanup;
 		}
 
 		/* last process global ignores */
 		git_vector_foreach(&ignores.ign_global, i, file) {
-			if (ignore_lookup_in_rules(&file->rules, &path, ignored))
+			if (ignore_lookup_in_rules(file, &path, ignored))
 				goto cleanup;
 		}
 
diff --git a/src/index.c b/src/index.c
index b0b5eae..083c01f 100644
--- a/src/index.c
+++ b/src/index.c
@@ -90,13 +90,24 @@ struct entry_long {
 
 struct entry_srch_key {
 	const char *path;
-	size_t path_len;
+	size_t pathlen;
 	int stage;
 };
 
+struct entry_internal {
+	git_index_entry entry;
+	size_t pathlen;
+	char path[GIT_FLEX_ARRAY];
+};
+
+struct reuc_entry_internal {
+	git_index_reuc_entry entry;
+	size_t pathlen;
+	char path[GIT_FLEX_ARRAY];
+};
+
 /* local declarations */
 static size_t read_extension(git_index *index, const char *buffer, size_t buffer_size);
-static size_t read_entry(git_index_entry *dest, const void *buffer, size_t buffer_size);
 static int read_header(struct index_header *dest, const void *buffer);
 
 static int parse_index(git_index *index, const char *buffer, size_t buffer_size);
@@ -106,15 +117,15 @@ static int write_index(git_index *index, git_filebuf *file);
 static void index_entry_free(git_index_entry *entry);
 static void index_entry_reuc_free(git_index_reuc_entry *reuc);
 
-static int index_srch(const void *key, const void *array_member)
+int git_index_entry_srch(const void *key, const void *array_member)
 {
 	const struct entry_srch_key *srch_key = key;
-	const git_index_entry *entry = array_member;
+	const struct entry_internal *entry = array_member;
 	int cmp;
 	size_t len1, len2, len;
 
-	len1 = srch_key->path_len;
-	len2 = strlen(entry->path);
+	len1 = srch_key->pathlen;
+	len2 = entry->pathlen;
 	len = len1 < len2 ? len1 : len2;
 
 	cmp = memcmp(srch_key->path, entry->path, len);
@@ -126,20 +137,20 @@ static int index_srch(const void *key, const void *array_member)
 		return 1;
 
 	if (srch_key->stage != GIT_INDEX_STAGE_ANY)
-		return srch_key->stage - GIT_IDXENTRY_STAGE(entry);
+		return srch_key->stage - GIT_IDXENTRY_STAGE(&entry->entry);
 
 	return 0;
 }
 
-static int index_isrch(const void *key, const void *array_member)
+int git_index_entry_isrch(const void *key, const void *array_member)
 {
 	const struct entry_srch_key *srch_key = key;
-	const git_index_entry *entry = array_member;
+	const struct entry_internal *entry = array_member;
 	int cmp;
 	size_t len1, len2, len;
 
-	len1 = srch_key->path_len;
-	len2 = strlen(entry->path);
+	len1 = srch_key->pathlen;
+	len2 = entry->pathlen;
 	len = len1 < len2 ? len1 : len2;
 
 	cmp = strncasecmp(srch_key->path, entry->path, len);
@@ -152,36 +163,26 @@ static int index_isrch(const void *key, const void *array_member)
 		return 1;
 
 	if (srch_key->stage != GIT_INDEX_STAGE_ANY)
-		return srch_key->stage - GIT_IDXENTRY_STAGE(entry);
+		return srch_key->stage - GIT_IDXENTRY_STAGE(&entry->entry);
 
 	return 0;
 }
 
-static int index_cmp_path(const void *a, const void *b)
-{
-	return strcmp((const char *)a, (const char *)b);
-}
-
-static int index_icmp_path(const void *a, const void *b)
-{
-	return strcasecmp((const char *)a, (const char *)b);
-}
-
-static int index_srch_path(const void *path, const void *array_member)
+static int index_entry_srch_path(const void *path, const void *array_member)
 {
 	const git_index_entry *entry = array_member;
 
 	return strcmp((const char *)path, entry->path);
 }
 
-static int index_isrch_path(const void *path, const void *array_member)
+static int index_entry_isrch_path(const void *path, const void *array_member)
 {
 	const git_index_entry *entry = array_member;
 
 	return strcasecmp((const char *)path, entry->path);
 }
 
-static int index_cmp(const void *a, const void *b)
+int git_index_entry_cmp(const void *a, const void *b)
 {
 	int diff;
 	const git_index_entry *entry_a = a;
@@ -195,7 +196,7 @@ static int index_cmp(const void *a, const void *b)
 	return diff;
 }
 
-static int index_icmp(const void *a, const void *b)
+int git_index_entry_icmp(const void *a, const void *b)
 {
 	int diff;
 	const git_index_entry *entry_a = a;
@@ -286,17 +287,12 @@ static int reuc_icmp(const void *a, const void *b)
 
 static void index_entry_reuc_free(git_index_reuc_entry *reuc)
 {
-	if (!reuc)
-		return;
-	git__free(reuc->path);
 	git__free(reuc);
 }
 
 static void index_entry_free(git_index_entry *entry)
 {
-	if (!entry)
-		return;
-	git__free(entry->path);
+	memset(&entry->id, 0, sizeof(entry->id));
 	git__free(entry);
 }
 
@@ -325,18 +321,69 @@ static unsigned int index_merge_mode(
 	return git_index__create_mode(mode);
 }
 
-void git_index__set_ignore_case(git_index *index, bool ignore_case)
+static int index_sort_if_needed(git_index *index, bool need_lock)
 {
-	index->ignore_case = ignore_case;
+	/* not truly threadsafe because between when this checks and/or
+	 * sorts the array another thread could come in and unsort it
+	 */
 
-	index->entries_cmp_path = ignore_case ? index_icmp_path : index_cmp_path;
-	index->entries_search = ignore_case ? index_isrch : index_srch;
-	index->entries_search_path = ignore_case ? index_isrch_path : index_srch_path;
+	if (git_vector_is_sorted(&index->entries))
+		return 0;
+
+	if (need_lock && git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to lock index");
+		return -1;
+	}
 
-	git_vector_set_cmp(&index->entries, ignore_case ? index_icmp : index_cmp);
 	git_vector_sort(&index->entries);
 
-	index->reuc_search = ignore_case ? reuc_isrch : reuc_srch;
+	if (need_lock)
+		git_mutex_unlock(&index->lock);
+
+	return 0;
+}
+
+GIT_INLINE(int) index_find_in_entries(
+	size_t *out, git_vector *entries, git_vector_cmp entry_srch,
+	const char *path, size_t path_len, int stage)
+{
+	struct entry_srch_key srch_key;
+	srch_key.path = path;
+	srch_key.pathlen = !path_len ? strlen(path) : path_len;
+	srch_key.stage = stage;
+	return git_vector_bsearch2(out, entries, entry_srch, &srch_key);
+}
+
+GIT_INLINE(int) index_find(
+	size_t *out, git_index *index,
+	const char *path, size_t path_len, int stage, bool need_lock)
+{
+	if (index_sort_if_needed(index, need_lock) < 0)
+		return -1;
+
+	return index_find_in_entries(
+		out, &index->entries, index->entries_search, path, path_len, stage);
+}
+
+void git_index__set_ignore_case(git_index *index, bool ignore_case)
+{
+	index->ignore_case = ignore_case;
+
+	if (ignore_case) {
+		index->entries_cmp_path    = git__strcasecmp_cb;
+		index->entries_search      = git_index_entry_isrch;
+		index->entries_search_path = index_entry_isrch_path;
+		index->reuc_search         = reuc_isrch;
+	} else {
+		index->entries_cmp_path    = git__strcmp_cb;
+		index->entries_search      = git_index_entry_srch;
+		index->entries_search_path = index_entry_srch_path;
+		index->reuc_search         = reuc_srch;
+	}
+
+	git_vector_set_cmp(&index->entries,
+		ignore_case ? git_index_entry_icmp : git_index_entry_cmp);
+	index_sort_if_needed(index, true);
 
 	git_vector_set_cmp(&index->reuc, ignore_case ? reuc_icmp : reuc_cmp);
 	git_vector_sort(&index->reuc);
@@ -345,41 +392,51 @@ void git_index__set_ignore_case(git_index *index, bool ignore_case)
 int git_index_open(git_index **index_out, const char *index_path)
 {
 	git_index *index;
-	int error;
+	int error = -1;
 
 	assert(index_out);
 
 	index = git__calloc(1, sizeof(git_index));
 	GITERR_CHECK_ALLOC(index);
 
+	if (git_mutex_init(&index->lock)) {
+		giterr_set(GITERR_OS, "Failed to initialize lock");
+		git__free(index);
+		return -1;
+	}
+
 	if (index_path != NULL) {
 		index->index_file_path = git__strdup(index_path);
-		GITERR_CHECK_ALLOC(index->index_file_path);
+		if (!index->index_file_path)
+			goto fail;
 
 		/* Check if index file is stored on disk already */
 		if (git_path_exists(index->index_file_path) == true)
 			index->on_disk = 1;
 	}
 
-	if (git_vector_init(&index->entries, 32, index_cmp) < 0 ||
-		git_vector_init(&index->names, 32, conflict_name_cmp) < 0 ||
-		git_vector_init(&index->reuc, 32, reuc_cmp) < 0)
-		return -1;
+	if (git_vector_init(&index->entries, 32, git_index_entry_cmp) < 0 ||
+		git_vector_init(&index->names, 8, conflict_name_cmp) < 0 ||
+		git_vector_init(&index->reuc, 8, reuc_cmp) < 0 ||
+		git_vector_init(&index->deleted, 8, git_index_entry_cmp) < 0)
+		goto fail;
 
-	index->entries_cmp_path = index_cmp_path;
-	index->entries_search = index_srch;
-	index->entries_search_path = index_srch_path;
+	index->entries_cmp_path = git__strcmp_cb;
+	index->entries_search = git_index_entry_srch;
+	index->entries_search_path = index_entry_srch_path;
 	index->reuc_search = reuc_srch;
 
-	if ((index_path != NULL) && ((error = git_index_read(index, true)) < 0)) {
-		git_index_free(index);
-		return error;
-	}
+	if (index_path != NULL && (error = git_index_read(index, true)) < 0)
+		goto fail;
 
 	*index_out = index;
 	GIT_REFCOUNT_INC(index);
 
 	return 0;
+
+fail:
+	git_index_free(index);
+	return error;
 }
 
 int git_index_new(git_index **out)
@@ -389,12 +446,19 @@ int git_index_new(git_index **out)
 
 static void index_free(git_index *index)
 {
+	/* index iterators increment the refcount of the index, so if we
+	 * get here then there should be no outstanding iterators.
+	 */
+	assert(!git_atomic_get(&index->readers));
+
 	git_index_clear(index);
 	git_vector_free(&index->entries);
 	git_vector_free(&index->names);
 	git_vector_free(&index->reuc);
+	git_vector_free(&index->deleted);
 
 	git__free(index->index_file_path);
+	git_mutex_free(&index->lock);
 
 	git__memzero(index, sizeof(*index));
 	git__free(index);
@@ -408,28 +472,71 @@ void git_index_free(git_index *index)
 	GIT_REFCOUNT_DEC(index, index_free);
 }
 
-static void index_entries_free(git_vector *entries)
+/* call with locked index */
+static void index_free_deleted(git_index *index)
 {
+	int readers = (int)git_atomic_get(&index->readers);
 	size_t i;
 
-	for (i = 0; i < entries->length; ++i)
-		index_entry_free(git__swap(entries->contents[i], NULL));
+	if (readers > 0 || !index->deleted.length)
+		return;
+
+	for (i = 0; i < index->deleted.length; ++i) {
+		git_index_entry *ie = git__swap(index->deleted.contents[i], NULL);
+		index_entry_free(ie);
+	}
 
-	git_vector_clear(entries);
+	git_vector_clear(&index->deleted);
 }
 
-void git_index_clear(git_index *index)
+/* call with locked index */
+static int index_remove_entry(git_index *index, size_t pos)
 {
+	int error = 0;
+	git_index_entry *entry = git_vector_get(&index->entries, pos);
+
+	if (entry != NULL)
+		git_tree_cache_invalidate_path(index->tree, entry->path);
+
+	error = git_vector_remove(&index->entries, pos);
+
+	if (!error) {
+		if (git_atomic_get(&index->readers) > 0) {
+			error = git_vector_insert(&index->deleted, entry);
+		} else {
+			index_entry_free(entry);
+		}
+	}
+
+	return error;
+}
+
+int git_index_clear(git_index *index)
+{
+	int error = 0;
+
 	assert(index);
 
-	index_entries_free(&index->entries);
+	git_tree_cache_free(index->tree);
+	index->tree = NULL;
+
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock index");
+		return -1;
+	}
+
+	while (!error && index->entries.length > 0)
+		error = index_remove_entry(index, index->entries.length - 1);
+	index_free_deleted(index);
+
 	git_index_reuc_clear(index);
 	git_index_name_clear(index);
 
 	git_futils_filestamp_set(&index->stamp, NULL);
 
-	git_tree_cache_free(index->tree);
-	index->tree = NULL;
+	git_mutex_unlock(&index->lock);
+
+	return error;
 }
 
 static int create_index_error(int error, const char *msg)
@@ -495,20 +602,29 @@ int git_index_read(git_index *index, int force)
 
 	if (!index->on_disk) {
 		if (force)
-			git_index_clear(index);
+			return git_index_clear(index);
 		return 0;
 	}
 
 	updated = git_futils_filestamp_check(&stamp, index->index_file_path);
-	if (updated < 0 || (!updated && !force))
+	if (updated < 0) {
+		giterr_set(
+			GITERR_INDEX,
+			"Failed to read index: '%s' no longer exists",
+			index->index_file_path);
 		return updated;
+	}
+	if (!updated && !force)
+		return 0;
 
 	error = git_futils_readbuffer(&buffer, index->index_file_path);
 	if (error < 0)
 		return error;
 
-	git_index_clear(index);
-	error = parse_index(index, buffer.ptr, buffer.size);
+	error = git_index_clear(index);
+
+	if (!error)
+		error = parse_index(index, buffer.ptr, buffer.size);
 
 	if (!error)
 		git_futils_filestamp_set(&index->stamp, &stamp);
@@ -538,7 +654,8 @@ int git_index_write(git_index *index)
 		return create_index_error(-1,
 			"Failed to read index: The index is in-memory only");
 
-	git_vector_sort(&index->entries);
+	if (index_sort_if_needed(index, true) < 0)
+		return -1;
 	git_vector_sort(&index->reuc);
 
 	if ((error = git_filebuf_open(
@@ -557,11 +674,11 @@ int git_index_write(git_index *index)
 	if ((error = git_filebuf_commit(&file)) < 0)
 		return error;
 
-	error = git_futils_filestamp_check(&index->stamp, index->index_file_path);
-	if (error < 0)
-		return error;
+	if (git_futils_filestamp_check(&index->stamp, index->index_file_path) < 0)
+		/* index could not be read from disk! */;
+	else
+		index->on_disk = 1;
 
-	index->on_disk = 1;
 	return 0;
 }
 
@@ -586,7 +703,8 @@ int git_index_write_tree(git_oid *oid, git_index *index)
 	return git_tree__write_index(oid, index, repo);
 }
 
-int git_index_write_tree_to(git_oid *oid, git_index *index, git_repository *repo)
+int git_index_write_tree_to(
+	git_oid *oid, git_index *index, git_repository *repo)
 {
 	assert(oid && index && repo);
 	return git_tree__write_index(oid, index, repo);
@@ -602,7 +720,8 @@ const git_index_entry *git_index_get_byindex(
 	git_index *index, size_t n)
 {
 	assert(index);
-	git_vector_sort(&index->entries);
+	if (index_sort_if_needed(index, true) < 0)
+		return NULL;
 	return git_vector_get(&index->entries, n);
 }
 
@@ -613,7 +732,7 @@ const git_index_entry *git_index_get_bypath(
 
 	assert(index);
 
-	if (git_index__find(&pos, index, path, 0, stage) < 0) {
+	if (index_find(&pos, index, path, 0, stage, true) < 0) {
 		giterr_set(GITERR_INDEX, "Index does not contain %s", path);
 		return NULL;
 	}
@@ -637,20 +756,19 @@ void git_index_entry__init_from_stat(
 	entry->file_size = st->st_size;
 }
 
-int git_index_entry__cmp(const void *a, const void *b)
+static git_index_entry *index_entry_alloc(const char *path)
 {
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcmp(entry_a->path, entry_b->path);
-}
+	size_t pathlen = strlen(path);
+	struct entry_internal *entry =
+		git__calloc(sizeof(struct entry_internal) + pathlen + 1, 1);
+	if (!entry)
+		return NULL;
 
-int git_index_entry__cmp_icase(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
+	entry->pathlen = pathlen;
+	memcpy(entry->path, path, pathlen);
+	entry->entry.path = entry->path;
 
-	return strcasecmp(entry_a->path, entry_b->path);
+	return (git_index_entry *)entry;
 }
 
 static int index_entry_init(
@@ -672,19 +790,31 @@ static int index_entry_init(
 	if (error < 0)
 		return error;
 
-	entry = git__calloc(1, sizeof(git_index_entry));
+	entry = index_entry_alloc(rel_path);
 	GITERR_CHECK_ALLOC(entry);
 
-	git_index_entry__init_from_stat(entry, &st, !index->distrust_filemode);
-
 	entry->id = oid;
-	entry->path = git__strdup(rel_path);
-	GITERR_CHECK_ALLOC(entry->path);
+	git_index_entry__init_from_stat(entry, &st, !index->distrust_filemode);
 
-	*entry_out = entry;
+	*entry_out = (git_index_entry *)entry;
 	return 0;
 }
 
+static git_index_reuc_entry *reuc_entry_alloc(const char *path)
+{
+	size_t pathlen = strlen(path);
+	struct reuc_entry_internal *entry =
+		git__calloc(sizeof(struct reuc_entry_internal) + pathlen + 1, 1);
+	if (!entry)
+		return NULL;
+
+	entry->pathlen = pathlen;
+	memcpy(entry->path, path, pathlen);
+	entry->entry.path = entry->path;
+
+	return (git_index_reuc_entry *)entry;
+}
+
 static int index_entry_reuc_init(git_index_reuc_entry **reuc_out,
 	const char *path,
 	int ancestor_mode, const git_oid *ancestor_oid,
@@ -695,15 +825,9 @@ static int index_entry_reuc_init(git_index_reuc_entry **reuc_out,
 
 	assert(reuc_out && path);
 
-	*reuc_out = NULL;
-
-	reuc = git__calloc(1, sizeof(git_index_reuc_entry));
+	*reuc_out = reuc = reuc_entry_alloc(path);
 	GITERR_CHECK_ALLOC(reuc);
 
-	reuc->path = git__strdup(path);
-	if (reuc->path == NULL)
-		return -1;
-
 	if ((reuc->mode[0] = ancestor_mode) > 0)
 		git_oid_cpy(&reuc->oid[0], ancestor_oid);
 
@@ -713,26 +837,31 @@ static int index_entry_reuc_init(git_index_reuc_entry **reuc_out,
 	if ((reuc->mode[2] = their_mode) > 0)
 		git_oid_cpy(&reuc->oid[2], their_oid);
 
-	*reuc_out = reuc;
 	return 0;
 }
 
-static git_index_entry *index_entry_dup(const git_index_entry *source_entry)
+static void index_entry_cpy(git_index_entry *tgt, const git_index_entry *src)
+{
+	char *tgt_path = tgt->path;
+	memcpy(tgt, src, sizeof(*tgt));
+	tgt->path = tgt_path; /* reset to existing path data */
+}
+
+static int index_entry_dup(git_index_entry **out, const git_index_entry *src)
 {
 	git_index_entry *entry;
 
-	entry = git__malloc(sizeof(git_index_entry));
-	if (!entry)
-		return NULL;
+	if (!src) {
+		*out = NULL;
+		return 0;
+	}
 
-	memcpy(entry, source_entry, sizeof(git_index_entry));
+	*out = entry = index_entry_alloc(src->path);
+	GITERR_CHECK_ALLOC(entry);
 
-	/* duplicate the path string so we own it */
-	entry->path = git__strdup(entry->path);
-	if (!entry->path)
-		return NULL;
+	index_entry_cpy(entry, src);
 
-	return entry;
+	return 0;
 }
 
 static int has_file_name(git_index *index,
@@ -744,20 +873,22 @@ static int has_file_name(git_index *index,
 	const char *name = entry->path;
 
 	while (pos < index->entries.length) {
-		git_index_entry *p = index->entries.contents[pos++];
+		struct entry_internal *p = index->entries.contents[pos++];
 
-		if (len >= strlen(p->path))
+		if (len >= p->pathlen)
 			break;
 		if (memcmp(name, p->path, len))
 			break;
-		if (GIT_IDXENTRY_STAGE(p) != stage)
+		if (GIT_IDXENTRY_STAGE(&p->entry) != stage)
 			continue;
 		if (p->path[len] != '/')
 			continue;
 		retval = -1;
 		if (!ok_to_replace)
 			break;
-		git_vector_remove(&index->entries, --pos);
+
+		if (index_remove_entry(index, --pos) < 0)
+			break;
 	}
 	return retval;
 }
@@ -775,7 +906,7 @@ static int has_dir_name(git_index *index,
 	const char *slash = name + strlen(name);
 
 	for (;;) {
-		size_t len, position;
+		size_t len, pos;
 
 		for (;;) {
 			if (*--slash == '/')
@@ -785,12 +916,13 @@ static int has_dir_name(git_index *index,
 		}
 		len = slash - name;
 
-		if (git_index__find(&position, index, name, len, stage) == 0) {
+		if (!index_find(&pos, index, name, len, stage, false)) {
 			retval = -1;
 			if (!ok_to_replace)
 				break;
 
-			git_vector_remove(&index->entries, position);
+			if (index_remove_entry(index, pos) < 0)
+				break;
 			continue;
 		}
 
@@ -799,20 +931,19 @@ static int has_dir_name(git_index *index,
 		 * already matches the sub-directory, then we know
 		 * we're ok, and we can exit.
 		 */
-		while (position < index->entries.length) {
-			git_index_entry *p = index->entries.contents[position];
+		for (; pos < index->entries.length; ++pos) {
+			struct entry_internal *p = index->entries.contents[pos];
 
-			if ((strlen(p->path) <= len) ||
-			    (p->path[len] != '/') ||
+			if (p->pathlen <= len ||
+			    p->path[len] != '/' ||
 			    memcmp(p->path, name, len))
 				break; /* not our subdirectory */
 
-			if (GIT_IDXENTRY_STAGE(p) == stage)
+			if (GIT_IDXENTRY_STAGE(&p->entry) == stage)
 				return retval;
-
-			position++;
 		}
 	}
+
 	return retval;
 }
 
@@ -823,22 +954,41 @@ static int check_file_directory_collision(git_index *index,
 	retval = retval + has_dir_name(index, entry, ok_to_replace);
 
 	if (retval) {
-		giterr_set(GITERR_INDEX, "'%s' appears as both a file an a directory", entry->path);
+		giterr_set(GITERR_INDEX,
+			"'%s' appears as both a file and a directory", entry->path);
 		return -1;
 	}
 
 	return 0;
 }
 
-static int index_insert(git_index *index, git_index_entry *entry, int replace)
+static int index_no_dups(void **old, void *new)
+{
+	const git_index_entry *entry = new;
+	GIT_UNUSED(old);
+	giterr_set(GITERR_INDEX, "'%s' appears multiple times at stage %d",
+		entry->path, GIT_IDXENTRY_STAGE(entry));
+	return GIT_EEXISTS;
+}
+
+/* index_insert takes ownership of the new entry - if it can't insert
+ * it, then it will return an error **and also free the entry**.  When
+ * it replaces an existing entry, it will update the entry_ptr with the
+ * actual entry in the index (and free the passed in one).
+ */
+static int index_insert(
+	git_index *index, git_index_entry **entry_ptr, int replace)
 {
+	int error = 0;
 	size_t path_length, position;
-	git_index_entry **existing = NULL;
+	git_index_entry *existing = NULL, *entry;
+
+	assert(index && entry_ptr);
 
-	assert(index && entry && entry->path != NULL);
+	entry = *entry_ptr;
 
 	/* make sure that the path length flag is correct */
-	path_length = strlen(entry->path);
+	path_length = ((struct entry_internal *)entry)->pathlen;
 
 	entry->flags &= ~GIT_IDXENTRY_NAMEMASK;
 
@@ -847,30 +997,51 @@ static int index_insert(git_index *index, git_index_entry *entry, int replace)
 	else
 		entry->flags |= GIT_IDXENTRY_NAMEMASK;
 
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to acquire index lock");
+		return -1;
+	}
+
+	git_vector_sort(&index->entries);
+
 	/* look if an entry with this path already exists */
-	if (!git_index__find(
-			&position, index, entry->path, 0, GIT_IDXENTRY_STAGE(entry))) {
-		existing = (git_index_entry **)&index->entries.contents[position];
+	if (!index_find(
+			&position, index, entry->path, 0, GIT_IDXENTRY_STAGE(entry), false)) {
+		existing = index->entries.contents[position];
 		/* update filemode to existing values if stat is not trusted */
-		entry->mode = index_merge_mode(index, *existing, entry->mode);
+		entry->mode = index_merge_mode(index, existing, entry->mode);
 	}
 
-	if (check_file_directory_collision(index, entry, position, replace) < 0)
-		return -1;
+	/* look for tree / blob name collisions, removing conflicts if requested */
+	error = check_file_directory_collision(index, entry, position, replace);
+	if (error < 0)
+		/* skip changes */;
 
-	/* if replacing is not requested or no existing entry exists, just
-	 * insert entry at the end; the index is no longer sorted
+	/* if we are replacing an existing item, overwrite the existing entry
+	 * and return it in place of the passed in one.
 	 */
-	if (!replace || !existing)
-		return git_vector_insert(&index->entries, entry);
+	else if (existing) {
+		if (replace)
+			index_entry_cpy(existing, entry);
+		index_entry_free(entry);
+		*entry_ptr = entry = existing;
+	}
+	else {
+		/* if replace is not requested or no existing entry exists, insert
+		 * at the sorted position.  (Since we re-sort after each insert to
+		 * check for dups, this is actually cheaper in the long run.)
+		 */
+		error = git_vector_insert_sorted(&index->entries, entry, index_no_dups);
+	}
 
-	/* exists, replace it (preserving name from existing entry) */
-	git__free(entry->path);
-	entry->path = (*existing)->path;
-	git__free(*existing);
-	*existing = entry;
+	if (error < 0) {
+		index_entry_free(*entry_ptr);
+		*entry_ptr = NULL;
+	}
 
-	return 0;
+	git_mutex_unlock(&index->lock);
+
+	return error;
 }
 
 static int index_conflict_to_reuc(git_index *index, const char *path)
@@ -907,19 +1078,15 @@ int git_index_add_bypath(git_index *index, const char *path)
 	assert(index && path);
 
 	if ((ret = index_entry_init(&entry, index, path)) < 0 ||
-		(ret = index_insert(index, entry, 1)) < 0)
-		goto on_error;
+		(ret = index_insert(index, &entry, 1)) < 0)
+		return ret;
 
 	/* Adding implies conflict was resolved, move conflict entries to REUC */
 	if ((ret = index_conflict_to_reuc(index, path)) < 0 && ret != GIT_ENOTFOUND)
-		goto on_error;
+		return ret;
 
 	git_tree_cache_invalidate_path(index->tree, entry->path);
 	return 0;
-
-on_error:
-	index_entry_free(entry);
-	return ret;
 }
 
 int git_index_remove_bypath(git_index *index, const char *path)
@@ -942,14 +1109,11 @@ int git_index_add(git_index *index, const git_index_entry *source_entry)
 	git_index_entry *entry = NULL;
 	int ret;
 
-	entry = index_entry_dup(source_entry);
-	if (entry == NULL)
-		return -1;
+	assert(index && source_entry && source_entry->path);
 
-	if ((ret = index_insert(index, entry, 1)) < 0) {
-		index_entry_free(entry);
+	if ((ret = index_entry_dup(&entry, source_entry)) < 0 ||
+		(ret = index_insert(index, &entry, 1)) < 0)
 		return ret;
-	}
 
 	git_tree_cache_invalidate_path(index->tree, entry->path);
 	return 0;
@@ -957,25 +1121,23 @@ int git_index_add(git_index *index, const git_index_entry *source_entry)
 
 int git_index_remove(git_index *index, const char *path, int stage)
 {
-	size_t position;
 	int error;
-	git_index_entry *entry;
+	size_t position;
 
-	if (git_index__find(&position, index, path, 0, stage) < 0) {
-		giterr_set(GITERR_INDEX, "Index does not contain %s at stage %d",
-			path, stage);
-		return GIT_ENOTFOUND;
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock index");
+		return -1;
 	}
 
-	entry = git_vector_get(&index->entries, position);
-	if (entry != NULL)
-		git_tree_cache_invalidate_path(index->tree, entry->path);
-
-	error = git_vector_remove(&index->entries, position);
-
-	if (!error)
-		index_entry_free(entry);
+	if (index_find(&position, index, path, 0, stage, false) < 0) {
+		giterr_set(
+			GITERR_INDEX, "Index does not contain %s at stage %d", path, stage);
+		error = GIT_ENOTFOUND;
+	} else {
+		error = index_remove_entry(index, position);
+	}
 
+	git_mutex_unlock(&index->lock);
 	return error;
 }
 
@@ -986,14 +1148,16 @@ int git_index_remove_directory(git_index *index, const char *dir, int stage)
 	size_t pos;
 	git_index_entry *entry;
 
-	if (git_buf_sets(&pfx, dir) < 0 || git_path_to_dir(&pfx) < 0)
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock index");
 		return -1;
+	}
 
-	git_vector_sort(&index->entries);
-
-	pos = git_index__prefix_position(index, pfx.ptr);
+	if (!(error = git_buf_sets(&pfx, dir)) &&
+		!(error = git_path_to_dir(&pfx)))
+		index_find(&pos, index, pfx.ptr, pfx.size, GIT_INDEX_STAGE_ANY, false);
 
-	while (1) {
+	while (!error) {
 		entry = git_vector_get(&index->entries, pos);
 		if (!entry || git__prefixcmp(entry->path, pfx.ptr) != 0)
 			break;
@@ -1003,35 +1167,22 @@ int git_index_remove_directory(git_index *index, const char *dir, int stage)
 			continue;
 		}
 
-		git_tree_cache_invalidate_path(index->tree, entry->path);
-
-		if ((error = git_vector_remove(&index->entries, pos)) < 0)
-			break;
-		index_entry_free(entry);
+		error = index_remove_entry(index, pos);
 
-		/* removed entry at 'pos' so we don't need to increment it */
+		/* removed entry at 'pos' so we don't need to increment */
 	}
 
+	git_mutex_unlock(&index->lock);
 	git_buf_free(&pfx);
 
 	return error;
 }
 
-int git_index__find(
+int git_index__find_pos(
 	size_t *out, git_index *index, const char *path, size_t path_len, int stage)
 {
-	struct entry_srch_key srch_key;
-
-	assert(path);
-
-	git_vector_sort(&index->entries);
-
-	srch_key.path = path;
-	srch_key.path_len = !path_len ? strlen(path) : path_len;
-	srch_key.stage = stage;
-
-	return git_vector_bsearch2(
-		out, &index->entries, index->entries_search, &srch_key);
+	assert(index && path);
+	return index_find(out, index, path, path_len, stage, true);
 }
 
 int git_index_find(size_t *at_pos, git_index *index, const char *path)
@@ -1040,7 +1191,14 @@ int git_index_find(size_t *at_pos, git_index *index, const char *path)
 
 	assert(index && path);
 
-	if (git_vector_bsearch2(&pos, &index->entries, index->entries_search_path, path) < 0) {
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock index");
+		return -1;
+	}
+
+	if (git_vector_bsearch2(
+			&pos, &index->entries, index->entries_search_path, path) < 0) {
+		git_mutex_unlock(&index->lock);
 		giterr_set(GITERR_INDEX, "Index does not contain %s", path);
 		return GIT_ENOTFOUND;
 	}
@@ -1048,37 +1206,20 @@ int git_index_find(size_t *at_pos, git_index *index, const char *path)
 	/* Since our binary search only looked at path, we may be in the
 	 * middle of a list of stages.
 	 */
-	while (pos > 0) {
-		const git_index_entry *prev = git_vector_get(&index->entries, pos-1);
+	for (; pos > 0; --pos) {
+		const git_index_entry *prev = git_vector_get(&index->entries, pos - 1);
 
 		if (index->entries_cmp_path(prev->path, path) != 0)
 			break;
-
-		--pos;
 	}
 
 	if (at_pos)
 		*at_pos = pos;
 
+	git_mutex_unlock(&index->lock);
 	return 0;
 }
 
-size_t git_index__prefix_position(git_index *index, const char *path)
-{
-	struct entry_srch_key srch_key;
-	size_t pos;
-
-	srch_key.path = path;
-	srch_key.path_len = strlen(path);
-	srch_key.stage = 0;
-
-	git_vector_sort(&index->entries);
-	git_vector_bsearch2(
-		&pos, &index->entries, index->entries_search, &srch_key);
-
-	return pos;
-}
-
 int git_index_conflict_add(git_index *index,
 	const git_index_entry *ancestor_entry,
 	const git_index_entry *our_entry,
@@ -1090,21 +1231,22 @@ int git_index_conflict_add(git_index *index,
 
 	assert (index);
 
-	if ((ancestor_entry != NULL && (entries[0] = index_entry_dup(ancestor_entry)) == NULL) ||
-		(our_entry != NULL && (entries[1] = index_entry_dup(our_entry)) == NULL) ||
-		(their_entry != NULL && (entries[2] = index_entry_dup(their_entry)) == NULL))
-		return -1;
+	if ((ret = index_entry_dup(&entries[0], ancestor_entry)) < 0 ||
+		(ret = index_entry_dup(&entries[1], our_entry)) < 0 ||
+		(ret = index_entry_dup(&entries[2], their_entry)) < 0)
+		goto on_error;
 
 	for (i = 0; i < 3; i++) {
 		if (entries[i] == NULL)
 			continue;
 
 		/* Make sure stage is correct */
-		entries[i]->flags = (entries[i]->flags & ~GIT_IDXENTRY_STAGEMASK) |
-			((i+1) << GIT_IDXENTRY_STAGESHIFT);
+		GIT_IDXENTRY_STAGE_SET(entries[i], i + 1);
 
-		if ((ret = index_insert(index, entries[i], 1)) < 0)
+		if ((ret = index_insert(index, &entries[i], 1)) < 0)
 			goto on_error;
+
+		entries[i] = NULL; /* don't free if later entry fails */
 	}
 
 	return 0;
@@ -1194,23 +1336,24 @@ int git_index_conflict_get(
 	return 0;
 }
 
-int git_index_conflict_remove(git_index *index, const char *path)
+static int index_conflict_remove(git_index *index, const char *path)
 {
-	size_t pos, posmax;
+	size_t pos = 0;
 	git_index_entry *conflict_entry;
 	int error = 0;
 
-	assert(index && path);
-
-	if (git_index_find(&pos, index, path) < 0)
+	if (path != NULL && git_index_find(&pos, index, path) < 0)
 		return GIT_ENOTFOUND;
 
-	posmax = git_index_entrycount(index);
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to lock index");
+		return -1;
+	}
 
-	while (pos < posmax) {
-		conflict_entry = git_vector_get(&index->entries, pos);
+	while ((conflict_entry = git_vector_get(&index->entries, pos)) != NULL) {
 
-		if (index->entries_cmp_path(conflict_entry->path, path) != 0)
+		if (path != NULL &&
+			index->entries_cmp_path(conflict_entry->path, path) != 0)
 			break;
 
 		if (GIT_IDXENTRY_STAGE(conflict_entry) == 0) {
@@ -1218,32 +1361,25 @@ int git_index_conflict_remove(git_index *index, const char *path)
 			continue;
 		}
 
-		if ((error = git_vector_remove(&index->entries, pos)) < 0)
-			return error;
-
-		index_entry_free(conflict_entry);
-		posmax--;
+		if ((error = index_remove_entry(index, pos)) < 0)
+			break;
 	}
 
-	return 0;
+	git_mutex_unlock(&index->lock);
+
+	return error;
 }
 
-static int index_conflicts_match(const git_vector *v, size_t idx)
+int git_index_conflict_remove(git_index *index, const char *path)
 {
-	git_index_entry *entry = git_vector_get(v, idx);
-
-	if (GIT_IDXENTRY_STAGE(entry) > 0) {
-		index_entry_free(entry);
-		return 1;
-	}
-
-	return 0;
+	assert(index && path);
+	return index_conflict_remove(index, path);
 }
 
-void git_index_conflict_cleanup(git_index *index)
+int git_index_conflict_cleanup(git_index *index)
 {
 	assert(index);
-	git_vector_remove_matching(&index->entries, index_conflicts_match);
+	return index_conflict_remove(index, NULL);
 }
 
 int git_index_has_conflicts(const git_index *index)
@@ -1338,32 +1474,36 @@ const git_index_name_entry *git_index_name_get_byindex(
 	return git_vector_get(&index->names, n);
 }
 
+static void index_name_entry_free(git_index_name_entry *ne)
+{
+	if (!ne)
+		return;
+	git__free(ne->ancestor);
+	git__free(ne->ours);
+	git__free(ne->theirs);
+	git__free(ne);
+}
+
 int git_index_name_add(git_index *index,
 	const char *ancestor, const char *ours, const char *theirs)
 {
 	git_index_name_entry *conflict_name;
 
-	assert ((ancestor && ours) || (ancestor && theirs) || (ours && theirs));
+	assert((ancestor && ours) || (ancestor && theirs) || (ours && theirs));
 
 	conflict_name = git__calloc(1, sizeof(git_index_name_entry));
 	GITERR_CHECK_ALLOC(conflict_name);
 
-	if (ancestor) {
-		conflict_name->ancestor = git__strdup(ancestor);
-		GITERR_CHECK_ALLOC(conflict_name->ancestor);
-	}
-
-	if (ours) {
-		conflict_name->ours = git__strdup(ours);
-		GITERR_CHECK_ALLOC(conflict_name->ours);
-	}
-
-	if (theirs) {
-		conflict_name->theirs = git__strdup(theirs);
-		GITERR_CHECK_ALLOC(conflict_name->theirs);
+	if ((ancestor && !(conflict_name->ancestor = git__strdup(ancestor))) ||
+		(ours     && !(conflict_name->ours     = git__strdup(ours))) ||
+		(theirs   && !(conflict_name->theirs   = git__strdup(theirs))) ||
+		git_vector_insert(&index->names, conflict_name) < 0)
+	{
+		index_name_entry_free(conflict_name);
+		return -1;
 	}
 
-	return git_vector_insert(&index->names, conflict_name);
+	return 0;
 }
 
 void git_index_name_clear(git_index *index)
@@ -1373,18 +1513,8 @@ void git_index_name_clear(git_index *index)
 
 	assert(index);
 
-	git_vector_foreach(&index->names, i, conflict_name) {
-		if (conflict_name->ancestor)
-			git__free(conflict_name->ancestor);
-
-		if (conflict_name->ours)
-			git__free(conflict_name->ours);
-
-		if (conflict_name->theirs)
-			git__free(conflict_name->theirs);
-
-		git__free(conflict_name);
-	}
+	git_vector_foreach(&index->names, i, conflict_name)
+		index_name_entry_free(conflict_name);
 
 	git_vector_clear(&index->names);
 }
@@ -1412,7 +1542,6 @@ static int index_reuc_insert(
 		return git_vector_insert(&index->reuc, reuc);
 
 	/* exists, replace it */
-	git__free((*existing)->path);
 	git__free(*existing);
 	*existing = reuc;
 
@@ -1429,15 +1558,13 @@ int git_index_reuc_add(git_index *index, const char *path,
 
 	assert(index && path);
 
-	if ((error = index_entry_reuc_init(&reuc, path, ancestor_mode, ancestor_oid, our_mode, our_oid, their_mode, their_oid)) < 0 ||
+	if ((error = index_entry_reuc_init(&reuc, path, ancestor_mode,
+			ancestor_oid, our_mode, our_oid, their_mode, their_oid)) < 0 ||
 		(error = index_reuc_insert(index, reuc, 1)) < 0)
-	{
 		index_entry_reuc_free(reuc);
-		return error;
-	}
 
 	return error;
-} 
+}
 
 int git_index_reuc_find(size_t *at_pos, git_index *index, const char *path)
 {
@@ -1522,13 +1649,9 @@ static int read_reuc(git_index *index, const char *buffer, size_t size)
 		if (size <= len)
 			return index_error_invalid("reading reuc entries");
 
-		lost = git__calloc(1, sizeof(git_index_reuc_entry));
+		lost = reuc_entry_alloc(buffer);
 		GITERR_CHECK_ALLOC(lost);
 
-		/* read NUL-terminated pathname for entry */
-		lost->path = git__strdup(buffer);
-		GITERR_CHECK_ALLOC(lost->path);
-
 		size -= len;
 		buffer += len;
 
@@ -1626,41 +1749,41 @@ static int read_conflict_names(git_index *index, const char *buffer, size_t size
 	return 0;
 }
 
-static size_t read_entry(git_index_entry *dest, const void *buffer, size_t buffer_size)
+static size_t read_entry(
+	git_index_entry **out, const void *buffer, size_t buffer_size)
 {
 	size_t path_length, entry_size;
 	uint16_t flags_raw;
 	const char *path_ptr;
 	const struct entry_short *source = buffer;
+	git_index_entry entry = {{0}};
 
 	if (INDEX_FOOTER_SIZE + minimal_entry_size > buffer_size)
 		return 0;
 
-	memset(dest, 0x0, sizeof(git_index_entry));
-
-	dest->ctime.seconds = (git_time_t)ntohl(source->ctime.seconds);
-	dest->ctime.nanoseconds = ntohl(source->ctime.nanoseconds);
-	dest->mtime.seconds = (git_time_t)ntohl(source->mtime.seconds);
-	dest->mtime.nanoseconds = ntohl(source->mtime.nanoseconds);
-	dest->dev = ntohl(source->dev);
-	dest->ino = ntohl(source->ino);
-	dest->mode = ntohl(source->mode);
-	dest->uid = ntohl(source->uid);
-	dest->gid = ntohl(source->gid);
-	dest->file_size = ntohl(source->file_size);
-	git_oid_cpy(&dest->id, &source->oid);
-	dest->flags = ntohs(source->flags);
-
-	if (dest->flags & GIT_IDXENTRY_EXTENDED) {
+	entry.ctime.seconds = (git_time_t)ntohl(source->ctime.seconds);
+	entry.ctime.nanoseconds = ntohl(source->ctime.nanoseconds);
+	entry.mtime.seconds = (git_time_t)ntohl(source->mtime.seconds);
+	entry.mtime.nanoseconds = ntohl(source->mtime.nanoseconds);
+	entry.dev = ntohl(source->dev);
+	entry.ino = ntohl(source->ino);
+	entry.mode = ntohl(source->mode);
+	entry.uid = ntohl(source->uid);
+	entry.gid = ntohl(source->gid);
+	entry.file_size = ntohl(source->file_size);
+	git_oid_cpy(&entry.id, &source->oid);
+	entry.flags = ntohs(source->flags);
+
+	if (entry.flags & GIT_IDXENTRY_EXTENDED) {
 		const struct entry_long *source_l = (const struct entry_long *)source;
 		path_ptr = source_l->path;
 
 		flags_raw = ntohs(source_l->flags_extended);
-		memcpy(&dest->flags_extended, &flags_raw, 2);
+		memcpy(&entry.flags_extended, &flags_raw, 2);
 	} else
 		path_ptr = source->path;
 
-	path_length = dest->flags & GIT_IDXENTRY_NAMEMASK;
+	path_length = entry.flags & GIT_IDXENTRY_NAMEMASK;
 
 	/* if this is a very long string, we must find its
 	 * real length without overflowing */
@@ -1674,7 +1797,7 @@ static size_t read_entry(git_index_entry *dest, const void *buffer, size_t buffe
 		path_length = path_end - path_ptr;
 	}
 
-	if (dest->flags & GIT_IDXENTRY_EXTENDED)
+	if (entry.flags & GIT_IDXENTRY_EXTENDED)
 		entry_size = long_entry_size(path_length);
 	else
 		entry_size = short_entry_size(path_length);
@@ -1682,8 +1805,10 @@ static size_t read_entry(git_index_entry *dest, const void *buffer, size_t buffe
 	if (INDEX_FOOTER_SIZE + entry_size > buffer_size)
 		return 0;
 
-	dest->path = git__strdup(path_ptr);
-	assert(dest->path);
+	entry.path = (char *)path_ptr;
+
+	if (index_entry_dup(out, &entry) < 0)
+		return 0;
 
 	return entry_size;
 }
@@ -1749,6 +1874,7 @@ static size_t read_extension(git_index *index, const char *buffer, size_t buffer
 
 static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 {
+	int error = 0;
 	unsigned int i;
 	struct index_header header = { 0 };
 	git_oid checksum_calculated, checksum_expected;
@@ -1768,35 +1894,41 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 	git_hash_buf(&checksum_calculated, buffer, buffer_size - INDEX_FOOTER_SIZE);
 
 	/* Parse header */
-	if (read_header(&header, buffer) < 0)
-		return -1;
+	if ((error = read_header(&header, buffer)) < 0)
+		return error;
 
 	seek_forward(INDEX_HEADER_SIZE);
 
-	git_vector_clear(&index->entries);
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Unable to acquire index lock");
+		return -1;
+	}
+
+	assert(!index->entries.length);
 
 	/* Parse all the entries */
 	for (i = 0; i < header.entry_count && buffer_size > INDEX_FOOTER_SIZE; ++i) {
-		size_t entry_size;
 		git_index_entry *entry;
-
-		entry = git__malloc(sizeof(git_index_entry));
-		GITERR_CHECK_ALLOC(entry);
-
-		entry_size = read_entry(entry, buffer, buffer_size);
+		size_t entry_size = read_entry(&entry, buffer, buffer_size);
 
 		/* 0 bytes read means an object corruption */
-		if (entry_size == 0)
-			return index_error_invalid("invalid entry");
+		if (entry_size == 0) {
+			error = index_error_invalid("invalid entry");
+			goto done;
+		}
 
-		if (git_vector_insert(&index->entries, entry) < 0)
-			return -1;
+		if ((error = git_vector_insert(&index->entries, entry)) < 0) {
+			index_entry_free(entry);
+			goto done;
+		}
 
 		seek_forward(entry_size);
 	}
 
-	if (i != header.entry_count)
-		return index_error_invalid("header entries changed while parsing");
+	if (i != header.entry_count) {
+		error = index_error_invalid("header entries changed while parsing");
+		goto done;
+	}
 
 	/* There's still space for some extensions! */
 	while (buffer_size > INDEX_FOOTER_SIZE) {
@@ -1805,20 +1937,28 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 		extension_size = read_extension(index, buffer, buffer_size);
 
 		/* see if we have read any bytes from the extension */
-		if (extension_size == 0)
-			return index_error_invalid("extension is truncated");
+		if (extension_size == 0) {
+			error = index_error_invalid("extension is truncated");
+			goto done;
+		}
 
 		seek_forward(extension_size);
 	}
 
-	if (buffer_size != INDEX_FOOTER_SIZE)
-		return index_error_invalid("buffer size does not match index footer size");
+	if (buffer_size != INDEX_FOOTER_SIZE) {
+		error = index_error_invalid(
+			"buffer size does not match index footer size");
+		goto done;
+	}
 
 	/* 160-bit SHA-1 over the content of the index file before this checksum. */
 	git_oid_fromraw(&checksum_expected, (const unsigned char *)buffer);
 
-	if (git_oid__cmp(&checksum_calculated, &checksum_expected) != 0)
-		return index_error_invalid("calculated checksum does not match expected");
+	if (git_oid__cmp(&checksum_calculated, &checksum_expected) != 0) {
+		error = index_error_invalid(
+			"calculated checksum does not match expected");
+		goto done;
+	}
 
 #undef seek_forward
 
@@ -1826,9 +1966,11 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 	 * in-memory index is supposed to be case-insensitive
 	 */
 	git_vector_set_sorted(&index->entries, !index->ignore_case);
-	git_vector_sort(&index->entries);
+	error = index_sort_if_needed(index, false);
 
-	return 0;
+done:
+	git_mutex_unlock(&index->lock);
+	return error;
 }
 
 static bool is_index_extended(git_index *index)
@@ -1856,7 +1998,7 @@ static int write_disk_entry(git_filebuf *file, git_index_entry *entry)
 	size_t path_len, disk_size;
 	char *path;
 
-	path_len = strlen(entry->path);
+	path_len = ((struct entry_internal *)entry)->pathlen;
 
 	if (entry->flags & GIT_IDXENTRY_EXTENDED)
 		disk_size = long_entry_size(path_len);
@@ -1913,22 +2055,30 @@ static int write_entries(git_index *index, git_filebuf *file)
 {
 	int error = 0;
 	size_t i;
-	git_vector case_sorted;
+	git_vector case_sorted, *entries;
 	git_index_entry *entry;
-	git_vector *out = &index->entries;
+
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock index");
+		return -1;
+	}
 
 	/* If index->entries is sorted case-insensitively, then we need
 	 * to re-sort it case-sensitively before writing */
 	if (index->ignore_case) {
-		git_vector_dup(&case_sorted, &index->entries, index_cmp);
+		git_vector_dup(&case_sorted, &index->entries, git_index_entry_cmp);
 		git_vector_sort(&case_sorted);
-		out = &case_sorted;
+		entries = &case_sorted;
+	} else {
+		entries = &index->entries;
 	}
 
-	git_vector_foreach(out, i, entry)
+	git_vector_foreach(entries, i, entry)
 		if ((error = write_disk_entry(file, entry)) < 0)
 			break;
 
+	git_mutex_unlock(&index->lock);
+
 	if (index->ignore_case)
 		git_vector_free(&case_sorted);
 
@@ -2100,7 +2250,7 @@ int git_index_entry_stage(const git_index_entry *entry)
 typedef struct read_tree_data {
 	git_vector *old_entries;
 	git_vector *new_entries;
-	git_vector_cmp entries_search;
+	git_vector_cmp entry_cmp;
 } read_tree_data;
 
 static int read_tree_cb(
@@ -2109,6 +2259,7 @@ static int read_tree_cb(
 	read_tree_data *data = payload;
 	git_index_entry *entry = NULL, *old_entry;
 	git_buf path = GIT_BUF_INIT;
+	size_t pos;
 
 	if (git_tree_entry__is_tree(tentry))
 		return 0;
@@ -2116,30 +2267,24 @@ static int read_tree_cb(
 	if (git_buf_joinpath(&path, root, tentry->filename) < 0)
 		return -1;
 
-	entry = git__calloc(1, sizeof(git_index_entry));
+	entry = index_entry_alloc(path.ptr);
 	GITERR_CHECK_ALLOC(entry);
 
 	entry->mode = tentry->attr;
 	entry->id = tentry->oid;
 
 	/* look for corresponding old entry and copy data to new entry */
-	if (data->old_entries) {
-		size_t pos;
-		struct entry_srch_key skey;
-
-		skey.path = path.ptr;
-		skey.path_len = strlen(path.ptr);
-		skey.stage = 0;
-
-		if (!git_vector_bsearch2(
-				&pos, data->old_entries, data->entries_search, &skey) &&
-			(old_entry = git_vector_get(data->old_entries, pos)) != NULL &&
-			entry->mode == old_entry->mode &&
-			git_oid_equal(&entry->id, &old_entry->id))
-		{
-			memcpy(entry, old_entry, sizeof(*entry));
-			entry->flags_extended = 0;
-		}
+	if (data->old_entries != NULL &&
+		!index_find_in_entries(
+			&pos, data->old_entries, data->entry_cmp, path.ptr, 0, 0) &&
+		(old_entry = git_vector_get(data->old_entries, pos)) != NULL &&
+		entry->mode == old_entry->mode &&
+		git_oid_equal(&entry->id, &old_entry->id))
+	{
+		char *oldpath = entry->path;
+		memcpy(entry, old_entry, sizeof(*entry));
+		entry->path = oldpath;
+		entry->flags_extended = 0;
 	}
 
 	if (path.size < GIT_IDXENTRY_NAMEMASK)
@@ -2147,7 +2292,6 @@ static int read_tree_cb(
 	else
 		entry->flags = GIT_IDXENTRY_NAMEMASK;
 
-	entry->path = git_buf_detach(&path);
 	git_buf_free(&path);
 
 	if (git_vector_insert(data->new_entries, entry) < 0) {
@@ -2168,16 +2312,25 @@ int git_index_read_tree(git_index *index, const git_tree *tree)
 
 	data.old_entries = &index->entries;
 	data.new_entries = &entries;
-	data.entries_search = index->entries_search;
+	data.entry_cmp   = index->entries_search;
 
-	git_vector_sort(&index->entries);
+	if (index_sort_if_needed(index, true) < 0)
+		return -1;
 
 	error = git_tree_walk(tree, GIT_TREEWALK_POST, read_tree_cb, &data);
 
 	if (!error) {
 		git_vector_sort(&entries);
-		git_index_clear(index);
-		git_vector_swap(&entries, &index->entries);
+
+		if ((error = git_index_clear(index)) < 0)
+			/* well, this isn't good */;
+		else if (git_mutex_lock(&index->lock) < 0) {
+			giterr_set(GITERR_OS, "Unable to acquire index lock");
+			error = -1;
+		} else {
+			git_vector_swap(&entries, &index->entries);
+			git_mutex_unlock(&index->lock);
+		}
 	}
 
 	git_vector_free(&entries);
@@ -2247,7 +2400,7 @@ int git_index_add_all(
 		/* skip ignored items that are not already in the index */
 		if ((flags & GIT_INDEX_ADD_FORCE) == 0 &&
 			git_iterator_current_is_ignored(wditer) &&
-			git_index__find(&existing, index, wd->path, 0, 0) < 0)
+			index_find(&existing, index, wd->path, 0, 0, true) < 0)
 			continue;
 
 		/* issue notification callback if requested */
@@ -2269,17 +2422,14 @@ int git_index_add_all(
 			break;
 
 		/* make the new entry to insert */
-		if ((entry = index_entry_dup(wd)) == NULL) {
-			error = -1;
+		if ((error = index_entry_dup(&entry, wd)) < 0)
 			break;
-		}
+
 		entry->id = blobid;
 
 		/* add working directory item to index */
-		if ((error = index_insert(index, entry, 1)) < 0) {
-			index_entry_free(entry);
+		if ((error = index_insert(index, &entry, 1)) < 0)
 			break;
-		}
 
 		git_tree_cache_invalidate_path(index->tree, wd->path);
 
@@ -2411,3 +2561,48 @@ int git_index_update_all(
 
 	return error;
 }
+
+int git_index_snapshot_new(git_vector *snap, git_index *index)
+{
+	int error;
+
+	GIT_REFCOUNT_INC(index);
+
+	if (git_mutex_lock(&index->lock) < 0) {
+		giterr_set(GITERR_OS, "Failed to lock index");
+		return -1;
+	}
+
+	git_atomic_inc(&index->readers);
+	git_vector_sort(&index->entries);
+
+	error = git_vector_dup(snap, &index->entries, index->entries._cmp);
+
+	git_mutex_unlock(&index->lock);
+
+	if (error < 0)
+		git_index_free(index);
+
+	return error;
+}
+
+void git_index_snapshot_release(git_vector *snap, git_index *index)
+{
+	git_vector_free(snap);
+
+	git_atomic_dec(&index->readers);
+
+	if (!git_mutex_lock(&index->lock)) {
+		index_free_deleted(index); /* try to free pending deleted items */
+		git_mutex_unlock(&index->lock);
+	}
+
+	git_index_free(index);
+}
+
+int git_index_snapshot_find(
+	size_t *out, git_vector *entries, git_vector_cmp entry_srch,
+	const char *path, size_t path_len, int stage)
+{
+	return index_find_in_entries(out, entries, entry_srch, path, path_len, stage);
+}
diff --git a/src/index.h b/src/index.h
index 17f04f0..50a0b4b 100644
--- a/src/index.h
+++ b/src/index.h
@@ -21,12 +21,15 @@ struct git_index {
 	git_refcount rc;
 
 	char *index_file_path;
-
 	git_futils_filestamp stamp;
+
 	git_vector entries;
 
-	unsigned int on_disk:1;
+	git_mutex  lock;    /* lock held while entries is being changed */
+	git_vector deleted; /* deleted entries if readers > 0 */
+	git_atomic readers; /* number of active iterators */
 
+	unsigned int on_disk:1;
 	unsigned int ignore_case:1;
 	unsigned int distrust_filemode:1;
 	unsigned int no_symlinks:1;
@@ -50,12 +53,21 @@ struct git_index_conflict_iterator {
 extern void git_index_entry__init_from_stat(
 	git_index_entry *entry, struct stat *st, bool trust_mode);
 
-extern size_t git_index__prefix_position(git_index *index, const char *path);
+/* Index entry comparison functions for array sorting */
+extern int git_index_entry_cmp(const void *a, const void *b);
+extern int git_index_entry_icmp(const void *a, const void *b);
 
-extern int git_index_entry__cmp(const void *a, const void *b);
-extern int git_index_entry__cmp_icase(const void *a, const void *b);
+/* Index entry search functions for search using a search spec */
+extern int git_index_entry_srch(const void *a, const void *b);
+extern int git_index_entry_isrch(const void *a, const void *b);
 
-extern int git_index__find(
+/* Search index for `path`, returning GIT_ENOTFOUND if it does not exist
+ * (but not setting an error message).
+ *
+ * `at_pos` is set to the position where it is or would be inserted.
+ * Pass `path_len` as strlen of path or 0 to call strlen internally.
+ */
+extern int git_index__find_pos(
 	size_t *at_pos, git_index *index, const char *path, size_t path_len, int stage);
 
 extern void git_index__set_ignore_case(git_index *index, bool ignore_case);
@@ -69,4 +81,16 @@ GIT_INLINE(const git_futils_filestamp *) git_index__filestamp(git_index *index)
 
 extern int git_index__changed_relative_to(git_index *index, const git_futils_filestamp *fs);
 
+/* Copy the current entries vector *and* increment the index refcount.
+ * Call `git_index__release_snapshot` when done.
+ */
+extern int git_index_snapshot_new(git_vector *snap, git_index *index);
+extern void git_index_snapshot_release(git_vector *snap, git_index *index);
+
+/* Allow searching in a snapshot; entries must already be sorted! */
+extern int git_index_snapshot_find(
+	size_t *at_pos, git_vector *snap, git_vector_cmp entry_srch,
+	const char *path, size_t path_len, int stage);
+
+
 #endif
diff --git a/src/iterator.c b/src/iterator.c
index a7a4491..63c14f9 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -644,6 +644,8 @@ typedef struct {
 	git_iterator base;
 	git_iterator_callbacks cb;
 	git_index *index;
+	git_vector entries;
+	git_vector_cmp entry_srch;
 	size_t current;
 	/* when not in autoexpand mode, use these to represent "tree" state */
 	git_buf partial;
@@ -654,10 +656,10 @@ typedef struct {
 
 static const git_index_entry *index_iterator__index_entry(index_iterator *ii)
 {
-	const git_index_entry *ie = git_index_get_byindex(ii->index, ii->current);
+	const git_index_entry *ie = git_vector_get(&ii->entries, ii->current);
 
 	if (ie != NULL && iterator__past_end(ii, ie->path)) {
-		ii->current = git_index_entrycount(ii->index);
+		ii->current = git_vector_length(&ii->entries);
 		ie = NULL;
 	}
 
@@ -726,7 +728,7 @@ static int index_iterator__current(
 	const git_index_entry **entry, git_iterator *self)
 {
 	index_iterator *ii = (index_iterator *)self;
-	const git_index_entry *ie = git_index_get_byindex(ii->index, ii->current);
+	const git_index_entry *ie = git_vector_get(&ii->entries, ii->current);
 
 	if (ie != NULL && index_iterator__at_tree(ii)) {
 		ii->tree_entry.path = ii->partial.ptr;
@@ -744,14 +746,14 @@ static int index_iterator__current(
 static int index_iterator__at_end(git_iterator *self)
 {
 	index_iterator *ii = (index_iterator *)self;
-	return (ii->current >= git_index_entrycount(ii->index));
+	return (ii->current >= git_vector_length(&ii->entries));
 }
 
 static int index_iterator__advance(
 	const git_index_entry **entry, git_iterator *self)
 {
 	index_iterator *ii = (index_iterator *)self;
-	size_t entrycount = git_index_entrycount(ii->index);
+	size_t entrycount = git_vector_length(&ii->entries);
 	const git_index_entry *ie;
 
 	if (!iterator__has_been_accessed(ii))
@@ -766,7 +768,7 @@ static int index_iterator__advance(
 			while (ii->current < entrycount) {
 				ii->current++;
 
-				if (!(ie = git_index_get_byindex(ii->index, ii->current)) ||
+				if (!(ie = git_vector_get(&ii->entries, ii->current)) ||
 					ii->base.prefixcomp(ie->path, ii->partial.ptr) != 0)
 					break;
 			}
@@ -789,7 +791,7 @@ static int index_iterator__advance_into(
 	const git_index_entry **entry, git_iterator *self)
 {
 	index_iterator *ii = (index_iterator *)self;
-	const git_index_entry *ie = git_index_get_byindex(ii->index, ii->current);
+	const git_index_entry *ie = git_vector_get(&ii->entries, ii->current);
 
 	if (ie != NULL && index_iterator__at_tree(ii)) {
 		if (ii->restore_terminator)
@@ -815,8 +817,11 @@ static int index_iterator__reset(
 	if (iterator__reset_range(self, start, end) < 0)
 		return -1;
 
-	ii->current = ii->base.start ?
-		git_index__prefix_position(ii->index, ii->base.start) : 0;
+	ii->current = 0;
+
+	if (ii->base.start)
+		git_index_snapshot_find(
+			&ii->current, &ii->entries, ii->entry_srch, ii->base.start, 0, 0);
 
 	if ((ie = index_iterator__skip_conflicts(ii)) == NULL)
 		return 0;
@@ -841,9 +846,8 @@ static int index_iterator__reset(
 static void index_iterator__free(git_iterator *self)
 {
 	index_iterator *ii = (index_iterator *)self;
-	git_index_free(ii->index);
+	git_index_snapshot_release(&ii->entries, ii->index);
 	ii->index = NULL;
-
 	git_buf_free(&ii->partial);
 }
 
@@ -854,18 +858,29 @@ int git_iterator_for_index(
 	const char *start,
 	const char *end)
 {
+	int error = 0;
 	index_iterator *ii = git__calloc(1, sizeof(index_iterator));
 	GITERR_CHECK_ALLOC(ii);
 
+	if ((error = git_index_snapshot_new(&ii->entries, index)) < 0) {
+		git__free(ii);
+		return error;
+	}
+	ii->index = index;
+
 	ITERATOR_BASE_INIT(ii, index, INDEX, git_index_owner(index));
 
-	if (index->ignore_case) {
-		ii->base.flags |= GIT_ITERATOR_IGNORE_CASE;
-		ii->base.prefixcomp = git__prefixcmp_icase;
+	if ((error = iterator__update_ignore_case((git_iterator *)ii, flags)) < 0) {
+		git_iterator_free((git_iterator *)ii);
+		return error;
 	}
 
-	ii->index = index;
-	GIT_REFCOUNT_INC(index);
+	ii->entry_srch = iterator__ignore_case(ii) ?
+		git_index_entry_isrch : git_index_entry_srch;
+
+	git_vector_set_cmp(&ii->entries, iterator__ignore_case(ii) ?
+		git_index_entry_icmp : git_index_entry_cmp);
+	git_vector_sort(&ii->entries);
 
 	git_buf_init(&ii->partial, 0);
 	ii->tree_entry.mode = GIT_FILEMODE_TREE;
@@ -873,7 +888,6 @@ int git_iterator_for_index(
 	index_iterator__reset((git_iterator *)ii, NULL, NULL);
 
 	*iter = (git_iterator *)ii;
-
 	return 0;
 }
 
diff --git a/src/merge.c b/src/merge.c
index 10c19b5..2e40b6d 100644
--- a/src/merge.c
+++ b/src/merge.c
@@ -995,10 +995,12 @@ static void merge_diff_list_coalesce_renames(
 	}
 }
 
-static int merge_diff_empty(const git_vector *conflicts, size_t idx)
+static int merge_diff_empty(const git_vector *conflicts, size_t idx, void *p)
 {
 	git_merge_diff *conflict = conflicts->contents[idx];
 
+	GIT_UNUSED(p);
+
 	return (!GIT_MERGE_INDEX_ENTRY_EXISTS(conflict->ancestor_entry) &&
 		!GIT_MERGE_INDEX_ENTRY_EXISTS(conflict->our_entry) &&
 		!GIT_MERGE_INDEX_ENTRY_EXISTS(conflict->their_entry));
@@ -1079,7 +1081,7 @@ int git_merge_diff_list__find_renames(
 	merge_diff_list_coalesce_renames(diff_list, similarity_ours, similarity_theirs, opts);
 
 	/* And remove any entries that were merged and are now empty. */
-	git_vector_remove_matching(&diff_list->conflicts, merge_diff_empty);
+	git_vector_remove_matching(&diff_list->conflicts, merge_diff_empty, NULL);
 
 done:
 	if (cache != NULL) {
@@ -1228,7 +1230,7 @@ done:
 	return error;
 }
 
-GIT_INLINE(int) index_entry_dup(
+GIT_INLINE(int) index_entry_dup_pool(
 	git_index_entry *out,
 	git_pool *pool,
 	const git_index_entry *src)
@@ -1274,9 +1276,9 @@ static git_merge_diff *merge_diff_from_index_entries(
 	if ((conflict = git_pool_malloc(pool, sizeof(git_merge_diff))) == NULL)
 		return NULL;
 
-	if (index_entry_dup(&conflict->ancestor_entry, pool, entries[TREE_IDX_ANCESTOR]) < 0 ||
-		index_entry_dup(&conflict->our_entry, pool, entries[TREE_IDX_OURS]) < 0 ||
-		index_entry_dup(&conflict->their_entry, pool, entries[TREE_IDX_THEIRS]) < 0)
+	if (index_entry_dup_pool(&conflict->ancestor_entry, pool, entries[TREE_IDX_ANCESTOR]) < 0 ||
+		index_entry_dup_pool(&conflict->our_entry, pool, entries[TREE_IDX_OURS]) < 0 ||
+		index_entry_dup_pool(&conflict->their_entry, pool, entries[TREE_IDX_THEIRS]) < 0)
 		return NULL;
 
 	conflict->our_status = merge_delta_type_from_index_entries(
@@ -1316,7 +1318,7 @@ static int merge_diff_list_insert_unmodified(
 	entry = git_pool_malloc(&diff_list->pool, sizeof(git_index_entry));
 	GITERR_CHECK_ALLOC(entry);
 
-	if ((error = index_entry_dup(entry, &diff_list->pool, tree_items[0])) >= 0)
+	if ((error = index_entry_dup_pool(entry, &diff_list->pool, tree_items[0])) >= 0)
 		error = git_vector_insert(&diff_list->staged, entry);
 
 	return error;
@@ -1330,7 +1332,7 @@ int git_merge_diff_list__find_differences(
 {
 	git_iterator *iterators[3] = {0};
 	const git_index_entry *items[3] = {0}, *best_cur_item, *cur_items[3];
-	git_vector_cmp entry_compare = git_index_entry__cmp;
+	git_vector_cmp entry_compare = git_index_entry_cmp;
 	struct merge_diff_df_data df_data = {0};
 	int cur_item_modified;
 	size_t i, j;
diff --git a/src/pathspec.c b/src/pathspec.c
index 4714884..09650de 100644
--- a/src/pathspec.c
+++ b/src/pathspec.c
@@ -445,7 +445,7 @@ static int pathspec_match_from_iterator(
 		/* check if path is ignored and untracked */
 		if (index != NULL &&
 			git_iterator_current_is_ignored(iter) &&
-			git_index__find(NULL, index, entry->path, 0, GIT_INDEX_STAGE_ANY) < 0)
+			git_index__find_pos(NULL, index, entry->path, 0, GIT_INDEX_STAGE_ANY) < 0)
 			continue;
 
 		/* mark the matched pattern as used */
diff --git a/src/repository.h b/src/repository.h
index 99923b6..86db488 100644
--- a/src/repository.h
+++ b/src/repository.h
@@ -108,7 +108,7 @@ struct git_repository {
 	git_submodule_cache *_submodules;
 
 	git_cache objects;
-	git_attr_cache attrcache;
+	git_attr_cache *attrcache;
 	git_diff_driver_registry *diff_drivers;
 
 	char *path_repository;
@@ -123,7 +123,7 @@ struct git_repository {
 
 GIT_INLINE(git_attr_cache *) git_repository_attr_cache(git_repository *repo)
 {
-	return &repo->attrcache;
+	return repo->attrcache;
 }
 
 int git_repository_head_tree(git_tree **tree, git_repository *repo);
diff --git a/src/sortedcache.c b/src/sortedcache.c
index 13f0921..c6b2261 100644
--- a/src/sortedcache.c
+++ b/src/sortedcache.c
@@ -20,7 +20,7 @@ int git_sortedcache_new(
 
 	if (git_pool_init(&sc->pool, 1, 0) < 0 ||
 		git_vector_init(&sc->items, 4, item_cmp) < 0 ||
-		(sc->map = git_strmap_alloc()) == NULL)
+		git_strmap_alloc(&sc->map) < 0)
 		goto fail;
 
 	if (git_rwlock_init(&sc->lock)) {
@@ -39,8 +39,7 @@ int git_sortedcache_new(
 	return 0;
 
 fail:
-	if (sc->map)
-		git_strmap_free(sc->map);
+	git_strmap_free(sc->map);
 	git_vector_free(&sc->items);
 	git_pool_clear(&sc->pool);
 	git__free(sc);
@@ -233,9 +232,8 @@ unlock:
 
 void git_sortedcache_updated(git_sortedcache *sc)
 {
-	 /* update filestamp to latest value */
-	if (git_futils_filestamp_check(&sc->stamp, sc->path) < 0)
-		giterr_clear();
+	/* update filestamp to latest value */
+	git_futils_filestamp_check(&sc->stamp, sc->path);
 }
 
 /* release all items in sorted cache */
diff --git a/src/strmap.h b/src/strmap.h
index 8276ab4..8985aaf 100644
--- a/src/strmap.h
+++ b/src/strmap.h
@@ -22,7 +22,9 @@ typedef khiter_t git_strmap_iter;
 #define GIT__USE_STRMAP \
 	__KHASH_IMPL(str, static kh_inline, const char *, void *, 1, kh_str_hash_func, kh_str_hash_equal)
 
-#define git_strmap_alloc()  kh_init(str)
+#define git_strmap_alloc(hp) \
+	((*(hp) = kh_init(str)) == NULL) ? giterr_set_oom(), -1 : 0
+
 #define git_strmap_free(h)  kh_destroy(str, h), h = NULL
 #define git_strmap_clear(h) kh_clear(str, h)
 
diff --git a/src/submodule.c b/src/submodule.c
index bea096d..5ddbfe8 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -1638,8 +1638,7 @@ static int submodule_cache_alloc(
 		return -1;
 	}
 
-	cache->submodules = git_strmap_alloc();
-	if (!cache->submodules) {
+	if (git_strmap_alloc(&cache->submodules) < 0) {
 		submodule_cache_free(cache);
 		return -1;
 	}
@@ -1694,8 +1693,6 @@ static int submodule_cache_refresh(git_submodule_cache *cache, int refresh)
 		update_gitmod = (wd != NULL) ?
 			git_futils_filestamp_check(&cache->gitmodules_stamp, path.ptr) :
 			(cache->gitmodules_stamp.mtime != 0);
-		if (update_gitmod < 0)
-			giterr_clear();
 	}
 
 	/* clear submodule flags that are to be refreshed */
diff --git a/src/thread-utils.h b/src/thread-utils.h
index 914c135..50d8610 100644
--- a/src/thread-utils.h
+++ b/src/thread-utils.h
@@ -47,6 +47,12 @@ typedef git_atomic git_atomic_ssize;
 #define git_thread_exit(status)	pthread_exit(status)
 #define git_thread_join(id, status) pthread_join(id, status)
 
+#if defined(GIT_WIN32)
+#define git_thread_yield() Sleep(0)
+#else
+#define git_thread_yield() sched_yield()
+#endif
+
 /* Pthreads Mutex */
 #define git_mutex pthread_mutex_t
 #define git_mutex_init(a)	pthread_mutex_init(a, NULL)
@@ -176,6 +182,7 @@ GIT_INLINE(int64_t) git_atomic64_add(git_atomic64 *a, int64_t addend)
 #define git_thread_kill(thread) (void)0
 #define git_thread_exit(status) (void)0
 #define git_thread_join(id, status) (void)0
+#define git_thread_yield() (void)0
 
 /* Pthreads Mutex */
 #define git_mutex unsigned int
diff --git a/src/tree-cache.c b/src/tree-cache.c
index 1d39971..49afd6e 100644
--- a/src/tree-cache.c
+++ b/src/tree-cache.c
@@ -7,23 +7,16 @@
 
 #include "tree-cache.h"
 
-static git_tree_cache *find_child(const git_tree_cache *tree, const char *path)
+static git_tree_cache *find_child(
+	const git_tree_cache *tree, const char *path, const char *end)
 {
-	size_t i, dirlen;
-	const char *end;
-
-	end = strchr(path, '/');
-	if (end == NULL) {
-		end = strrchr(path, '\0');
-	}
-
-	dirlen = end - path;
+	size_t i, dirlen = end ? (size_t)(end - path) : strlen(path);
 
 	for (i = 0; i < tree->children_count; ++i) {
-		const char *childname = tree->children[i]->name;
+		git_tree_cache *child = tree->children[i];
 
-		if (strlen(childname) == dirlen && !memcmp(path, childname, dirlen))
-			return tree->children[i];
+		if (child->namelen == dirlen && !memcmp(path, child->name, dirlen))
+			return child;
 	}
 
 	return NULL;
@@ -44,7 +37,7 @@ void git_tree_cache_invalidate_path(git_tree_cache *tree, const char *path)
 		if (end == NULL) /* End of path */
 			break;
 
-		tree = find_child(tree, ptr);
+		tree = find_child(tree, ptr, end);
 		if (tree == NULL) /* We don't have that tree */
 			return;
 
@@ -64,10 +57,9 @@ const git_tree_cache *git_tree_cache_get(const git_tree_cache *tree, const char 
 	while (1) {
 		end = strchr(ptr, '/');
 
-		tree = find_child(tree, ptr);
-		if (tree == NULL) { /* Can't find it */
+		tree = find_child(tree, ptr, end);
+		if (tree == NULL) /* Can't find it */
 			return NULL;
-		}
 
 		if (end == NULL || *end + 1 == '\0')
 			return tree;
@@ -100,6 +92,7 @@ static int read_tree_internal(git_tree_cache **out,
 	tree->parent = parent;
 
 	/* NUL-terminated tree name */
+	tree->namelen = name_len;
 	memcpy(tree->name, name_start, name_len);
 	tree->name[name_len] = '\0';
 
diff --git a/src/tree-cache.h b/src/tree-cache.h
index 805483a..90c82db 100644
--- a/src/tree-cache.h
+++ b/src/tree-cache.h
@@ -18,6 +18,7 @@ struct git_tree_cache {
 
 	ssize_t entries;
 	git_oid oid;
+	size_t namelen;
 	char name[GIT_FLEX_ARRAY];
 };
 
diff --git a/src/util.c b/src/util.c
index 3767b89..3985825 100644
--- a/src/util.c
+++ b/src/util.c
@@ -542,10 +542,12 @@ int git__bsearch_r(
  */
 int git__strcmp_cb(const void *a, const void *b)
 {
-	const char *stra = (const char *)a;
-	const char *strb = (const char *)b;
+	return strcmp((const char *)a, (const char *)b);
+}
 
-	return strcmp(stra, strb);
+int git__strcasecmp_cb(const void *a, const void *b)
+{
+	return strcasecmp((const char *)a, (const char *)b);
 }
 
 int git__parse_bool(int *out, const char *value)
diff --git a/src/util.h b/src/util.h
index 5c2c563..d94463c 100644
--- a/src/util.h
+++ b/src/util.h
@@ -196,6 +196,7 @@ extern int git__bsearch_r(
 	size_t *position);
 
 extern int git__strcmp_cb(const void *a, const void *b);
+extern int git__strcasecmp_cb(const void *a, const void *b);
 
 extern int git__strcmp(const char *a, const char *b);
 extern int git__strcasecmp(const char *a, const char *b);
diff --git a/src/vector.c b/src/vector.c
index 37ea07f..c769b69 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -177,7 +177,8 @@ void git_vector_sort(git_vector *v)
 	if (git_vector_is_sorted(v) || !v->_cmp)
 		return;
 
-	git__tsort(v->contents, v->length, v->_cmp);
+	if (v->length > 1)
+		git__tsort(v->contents, v->length, v->_cmp);
 	git_vector_set_sorted(v, 1);
 }
 
@@ -276,14 +277,16 @@ void git_vector_uniq(git_vector *v, void  (*git_free_cb)(void *))
 }
 
 void git_vector_remove_matching(
-	git_vector *v, int (*match)(const git_vector *v, size_t idx))
+	git_vector *v,
+	int (*match)(const git_vector *v, size_t idx, void *payload),
+	void *payload)
 {
 	size_t i, j;
 
 	for (i = 0, j = 0; j < v->length; ++j) {
 		v->contents[i] = v->contents[j];
 
-		if (!match(v, i))
+		if (!match(v, i, payload))
 			i++;
 	}
 
@@ -339,3 +342,18 @@ int git_vector_set(void **old, git_vector *v, size_t position, void *value)
 
 	return 0;
 }
+
+int git_vector_verify_sorted(const git_vector *v)
+{
+	size_t i;
+
+	if (!git_vector_is_sorted(v))
+		return -1;
+
+	for (i = 1; i < v->length; ++i) {
+		if (v->_cmp(v->contents[i - 1], v->contents[i]) > 0)
+			return -1;
+	}
+
+	return 0;
+}
diff --git a/src/vector.h b/src/vector.h
index 682b6ad..aac46c4 100644
--- a/src/vector.h
+++ b/src/vector.h
@@ -85,8 +85,11 @@ int git_vector_insert_sorted(git_vector *v, void *element,
 int git_vector_remove(git_vector *v, size_t idx);
 void git_vector_pop(git_vector *v);
 void git_vector_uniq(git_vector *v, void  (*git_free_cb)(void *));
+
 void git_vector_remove_matching(
-	git_vector *v, int (*match)(const git_vector *v, size_t idx));
+	git_vector *v,
+	int (*match)(const git_vector *v, size_t idx, void *payload),
+	void *payload);
 
 int git_vector_resize_to(git_vector *v, size_t new_length);
 int git_vector_set(void **old, git_vector *v, size_t position, void *value);
@@ -108,4 +111,7 @@ GIT_INLINE(void) git_vector_set_cmp(git_vector *v, git_vector_cmp cmp)
 	}
 }
 
+/* Just use this in tests, not for realz. returns -1 if not sorted */
+int git_vector_verify_sorted(const git_vector *v);
+
 #endif
diff --git a/tests/attr/file.c b/tests/attr/file.c
index 4eb1d22..1f4108c 100644
--- a/tests/attr/file.c
+++ b/tests/attr/file.c
@@ -11,9 +11,9 @@ void test_attr_file__simple_read(void)
 	git_attr_assignment *assign;
 	git_attr_rule *rule;
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr0")));
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr0")));
 
-	cl_assert_equal_s(cl_fixture("attr/attr0"), file->key + 2);
+	cl_assert_equal_s(cl_fixture("attr/attr0"), file->entry->path);
 	cl_assert(file->rules.length == 1);
 
 	rule = get_rule(0);
@@ -37,9 +37,9 @@ void test_attr_file__match_variants(void)
 	git_attr_rule *rule;
 	git_attr_assignment *assign;
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr1")));
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr1")));
 
-	cl_assert_equal_s(cl_fixture("attr/attr1"), file->key + 2);
+	cl_assert_equal_s(cl_fixture("attr/attr1"), file->entry->path);
 	cl_assert(file->rules.length == 10);
 
 	/* let's do a thorough check of this rule, then just verify
@@ -121,9 +121,9 @@ void test_attr_file__assign_variants(void)
 	git_attr_rule *rule;
 	git_attr_assignment *assign;
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr2")));
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr2")));
 
-	cl_assert_equal_s(cl_fixture("attr/attr2"), file->key + 2);
+	cl_assert_equal_s(cl_fixture("attr/attr2"), file->entry->path);
 	cl_assert(file->rules.length == 11);
 
 	check_one_assign(file, 0, 0, "pat0", "simple", EXPECT_TRUE, NULL);
@@ -187,8 +187,8 @@ void test_attr_file__check_attr_examples(void)
 	git_attr_rule *rule;
 	git_attr_assignment *assign;
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr3")));
-	cl_assert_equal_s(cl_fixture("attr/attr3"), file->key + 2);
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr3")));
+	cl_assert_equal_s(cl_fixture("attr/attr3"), file->entry->path);
 	cl_assert(file->rules.length == 3);
 
 	rule = get_rule(0);
diff --git a/tests/attr/lookup.c b/tests/attr/lookup.c
index 200bdd2..030ea07 100644
--- a/tests/attr/lookup.c
+++ b/tests/attr/lookup.c
@@ -9,8 +9,8 @@ void test_attr_lookup__simple(void)
 	git_attr_path path;
 	const char *value = NULL;
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr0")));
-	cl_assert_equal_s(cl_fixture("attr/attr0"), file->key + 2);
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr0")));
+	cl_assert_equal_s(cl_fixture("attr/attr0"), file->entry->path);
 	cl_assert(file->rules.length == 1);
 
 	cl_git_pass(git_attr_path__init(&path, "test", NULL));
@@ -129,8 +129,8 @@ void test_attr_lookup__match_variants(void)
 		{ NULL, NULL, 0, NULL }
 	};
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr1")));
-	cl_assert_equal_s(cl_fixture("attr/attr1"), file->key + 2);
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr1")));
+	cl_assert_equal_s(cl_fixture("attr/attr1"), file->entry->path);
 	cl_assert(file->rules.length == 10);
 
 	cl_git_pass(git_attr_path__init(&path, "/testing/for/pat0", NULL));
@@ -190,7 +190,7 @@ void test_attr_lookup__assign_variants(void)
 		{ NULL, NULL, 0, NULL }
 	};
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr2")));
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr2")));
 	cl_assert(file->rules.length == 11);
 
 	run_test_cases(file, cases, 0);
@@ -225,7 +225,7 @@ void test_attr_lookup__check_attr_examples(void)
 		{ NULL, NULL, 0, NULL }
 	};
 
-	cl_git_pass(git_attr_file__new_and_load(&file, cl_fixture("attr/attr3")));
+	cl_git_pass(git_attr_file__load_standalone(&file, cl_fixture("attr/attr3")));
 	cl_assert(file->rules.length == 3);
 
 	run_test_cases(file, cases, 0);
@@ -250,9 +250,9 @@ void test_attr_lookup__from_buffer(void)
 		{ NULL, NULL, 0, NULL }
 	};
 
-	cl_git_pass(git_attr_file__new(&file, 0, NULL, NULL));
+	cl_git_pass(git_attr_file__new(&file, NULL, 0));
 
-	cl_git_pass(git_attr_file__parse_buffer(NULL, NULL, "a* foo\nabc bar\n* baz", file));
+	cl_git_pass(git_attr_file__parse_buffer(NULL, file, "a* foo\nabc bar\n* baz"));
 
 	cl_assert(file->rules.length == 3);
 
diff --git a/tests/attr/repo.c b/tests/attr/repo.c
index 49cccdc..71dc7a5 100644
--- a/tests/attr/repo.c
+++ b/tests/attr/repo.c
@@ -68,9 +68,12 @@ void test_attr_repo__get_one(void)
 		attr_check_expected(scan->expected, scan->expected_str, scan->attr, value);
 	}
 
-	cl_assert(git_attr_cache__is_cached(g_repo, 0, ".git/info/attributes"));
-	cl_assert(git_attr_cache__is_cached(g_repo, 0, ".gitattributes"));
-	cl_assert(git_attr_cache__is_cached(g_repo, 0, "sub/.gitattributes"));
+	cl_assert(git_attr_cache__is_cached(
+		g_repo, GIT_ATTR_FILE__FROM_FILE, ".git/info/attributes"));
+	cl_assert(git_attr_cache__is_cached(
+		g_repo, GIT_ATTR_FILE__FROM_FILE, ".gitattributes"));
+	cl_assert(git_attr_cache__is_cached(
+		g_repo, GIT_ATTR_FILE__FROM_FILE, "sub/.gitattributes"));
 }
 
 void test_attr_repo__get_many(void)
diff --git a/tests/clar_libgit2.h b/tests/clar_libgit2.h
index c2489db..d395bd6 100644
--- a/tests/clar_libgit2.h
+++ b/tests/clar_libgit2.h
@@ -11,7 +11,7 @@
  *
  * Use this wrapper around all `git_` library calls that return error codes!
  */
-#define cl_git_pass(expr) cl_git_pass_(expr, __FILE__, __LINE__)
+#define cl_git_pass(expr) cl_git_pass_((expr), __FILE__, __LINE__)
 
 #define cl_git_pass_(expr, file, line) do { \
 	int _lg2_error; \
diff --git a/tests/core/strmap.c b/tests/core/strmap.c
index f34a4f8..a120f1f 100644
--- a/tests/core/strmap.c
+++ b/tests/core/strmap.c
@@ -3,12 +3,22 @@
 
 GIT__USE_STRMAP;
 
+git_strmap *g_table;
+
+void test_core_strmap__initialize(void)
+{
+	cl_git_pass(git_strmap_alloc(&g_table));
+	cl_assert(g_table != NULL);
+}
+
+void test_core_strmap__cleanup(void)
+{
+	git_strmap_free(g_table);
+}
+
 void test_core_strmap__0(void)
 {
-	git_strmap *table = git_strmap_alloc();
-	cl_assert(table != NULL);
-	cl_assert(git_strmap_num_entries(table) == 0);
-	git_strmap_free(table);
+	cl_assert(git_strmap_num_entries(g_table) == 0);
 }
 
 static void insert_strings(git_strmap *table, int count)
@@ -37,21 +47,17 @@ void test_core_strmap__1(void)
 {
 	int i;
 	char *str;
-	git_strmap *table = git_strmap_alloc();
-	cl_assert(table != NULL);
 
-	insert_strings(table, 20);
+	insert_strings(g_table, 20);
 
-	cl_assert(git_strmap_exists(table, "aaaaaaaaa"));
-	cl_assert(git_strmap_exists(table, "ggggggggg"));
-	cl_assert(!git_strmap_exists(table, "aaaaaaaab"));
-	cl_assert(!git_strmap_exists(table, "abcdefghi"));
+	cl_assert(git_strmap_exists(g_table, "aaaaaaaaa"));
+	cl_assert(git_strmap_exists(g_table, "ggggggggg"));
+	cl_assert(!git_strmap_exists(g_table, "aaaaaaaab"));
+	cl_assert(!git_strmap_exists(g_table, "abcdefghi"));
 
 	i = 0;
-	git_strmap_foreach_value(table, str, { i++; free(str); });
+	git_strmap_foreach_value(g_table, str, { i++; free(str); });
 	cl_assert(i == 20);
-
-	git_strmap_free(table);
 }
 
 void test_core_strmap__2(void)
@@ -59,44 +65,36 @@ void test_core_strmap__2(void)
 	khiter_t pos;
 	int i;
 	char *str;
-	git_strmap *table = git_strmap_alloc();
-	cl_assert(table != NULL);
 
-	insert_strings(table, 20);
+	insert_strings(g_table, 20);
 
-	cl_assert(git_strmap_exists(table, "aaaaaaaaa"));
-	cl_assert(git_strmap_exists(table, "ggggggggg"));
-	cl_assert(!git_strmap_exists(table, "aaaaaaaab"));
-	cl_assert(!git_strmap_exists(table, "abcdefghi"));
+	cl_assert(git_strmap_exists(g_table, "aaaaaaaaa"));
+	cl_assert(git_strmap_exists(g_table, "ggggggggg"));
+	cl_assert(!git_strmap_exists(g_table, "aaaaaaaab"));
+	cl_assert(!git_strmap_exists(g_table, "abcdefghi"));
 
-	cl_assert(git_strmap_exists(table, "bbbbbbbbb"));
-	pos = git_strmap_lookup_index(table, "bbbbbbbbb");
-	cl_assert(git_strmap_valid_index(table, pos));
-	cl_assert_equal_s(git_strmap_value_at(table, pos), "bbbbbbbbb");
-	free(git_strmap_value_at(table, pos));
-	git_strmap_delete_at(table, pos);
+	cl_assert(git_strmap_exists(g_table, "bbbbbbbbb"));
+	pos = git_strmap_lookup_index(g_table, "bbbbbbbbb");
+	cl_assert(git_strmap_valid_index(g_table, pos));
+	cl_assert_equal_s(git_strmap_value_at(g_table, pos), "bbbbbbbbb");
+	free(git_strmap_value_at(g_table, pos));
+	git_strmap_delete_at(g_table, pos);
 
-	cl_assert(!git_strmap_exists(table, "bbbbbbbbb"));
+	cl_assert(!git_strmap_exists(g_table, "bbbbbbbbb"));
 
 	i = 0;
-	git_strmap_foreach_value(table, str, { i++; free(str); });
+	git_strmap_foreach_value(g_table, str, { i++; free(str); });
 	cl_assert(i == 19);
-
-	git_strmap_free(table);
 }
 
 void test_core_strmap__3(void)
 {
 	int i;
 	char *str;
-	git_strmap *table = git_strmap_alloc();
-	cl_assert(table != NULL);
 
-	insert_strings(table, 10000);
+	insert_strings(g_table, 10000);
 
 	i = 0;
-	git_strmap_foreach_value(table, str, { i++; free(str); });
+	git_strmap_foreach_value(g_table, str, { i++; free(str); });
 	cl_assert(i == 10000);
-
-	git_strmap_free(table);
 }
diff --git a/tests/core/vector.c b/tests/core/vector.c
index db52c00..66f90b8 100644
--- a/tests/core/vector.c
+++ b/tests/core/vector.c
@@ -190,8 +190,9 @@ void test_core_vector__5(void)
 	git_vector_free(&x);
 }
 
-static int remove_ones(const git_vector *v, size_t idx)
+static int remove_ones(const git_vector *v, size_t idx, void *p)
 {
+	GIT_UNUSED(p);
 	return (git_vector_get(v, idx) == (void *)0x001);
 }
 
@@ -206,7 +207,7 @@ void test_core_vector__remove_matching(void)
 	git_vector_insert(&x, (void*) 0x001);
 
 	cl_assert(x.length == 1);
-	git_vector_remove_matching(&x, remove_ones);
+	git_vector_remove_matching(&x, remove_ones, NULL);
 	cl_assert(x.length == 0);
 
 	git_vector_insert(&x, (void*) 0x001);
@@ -214,7 +215,7 @@ void test_core_vector__remove_matching(void)
 	git_vector_insert(&x, (void*) 0x001);
 
 	cl_assert(x.length == 3);
-	git_vector_remove_matching(&x, remove_ones);
+	git_vector_remove_matching(&x, remove_ones, NULL);
 	cl_assert(x.length == 0);
 
 	git_vector_insert(&x, (void*) 0x002);
@@ -223,7 +224,7 @@ void test_core_vector__remove_matching(void)
 	git_vector_insert(&x, (void*) 0x001);
 
 	cl_assert(x.length == 4);
-	git_vector_remove_matching(&x, remove_ones);
+	git_vector_remove_matching(&x, remove_ones, NULL);
 	cl_assert(x.length == 2);
 
 	git_vector_foreach(&x, i, compare) {
@@ -238,7 +239,7 @@ void test_core_vector__remove_matching(void)
 	git_vector_insert(&x, (void*) 0x001);
 
 	cl_assert(x.length == 4);
-	git_vector_remove_matching(&x, remove_ones);
+	git_vector_remove_matching(&x, remove_ones, NULL);
 	cl_assert(x.length == 2);
 
 	git_vector_foreach(&x, i, compare) {
@@ -253,7 +254,7 @@ void test_core_vector__remove_matching(void)
 	git_vector_insert(&x, (void*) 0x001);
 
 	cl_assert(x.length == 4);
-	git_vector_remove_matching(&x, remove_ones);
+	git_vector_remove_matching(&x, remove_ones, NULL);
 	cl_assert(x.length == 2);
 
 	git_vector_foreach(&x, i, compare) {
@@ -268,7 +269,7 @@ void test_core_vector__remove_matching(void)
 	git_vector_insert(&x, (void*) 0x003);
 
 	cl_assert(x.length == 4);
-	git_vector_remove_matching(&x, remove_ones);
+	git_vector_remove_matching(&x, remove_ones, NULL);
 	cl_assert(x.length == 4);
 
 	git_vector_free(&x);
diff --git a/tests/diff/diff_helpers.c b/tests/diff/diff_helpers.c
index 33bb561..279cb20 100644
--- a/tests/diff/diff_helpers.c
+++ b/tests/diff/diff_helpers.c
@@ -1,5 +1,6 @@
 #include "clar_libgit2.h"
 #include "diff_helpers.h"
+#include "git2/sys/diff.h"
 
 git_tree *resolve_commit_oid_to_tree(
 	git_repository *repo,
@@ -215,32 +216,16 @@ abort:
 	return GIT_EUSER;
 }
 
-static int diff_print_cb(
-	const git_diff_delta *delta,
-	const git_diff_hunk *hunk,
-	const git_diff_line *line,
-	void *payload)
-{
-	FILE *fp = payload;
-
-	GIT_UNUSED(delta); GIT_UNUSED(hunk);
-
-	if (line->origin == GIT_DIFF_LINE_CONTEXT ||
-		line->origin == GIT_DIFF_LINE_ADDITION ||
-		line->origin == GIT_DIFF_LINE_DELETION)
-		fputc(line->origin, fp);
-	fwrite(line->content, 1, line->content_len, fp);
-	return 0;
-}
-
 void diff_print(FILE *fp, git_diff *diff)
 {
-	cl_git_pass(git_diff_print(
-		diff, GIT_DIFF_FORMAT_PATCH, diff_print_cb, fp ? fp : stderr));
+	cl_git_pass(
+		git_diff_print(diff, GIT_DIFF_FORMAT_PATCH,
+			git_diff_print_callback__to_file_handle, fp ? fp : stderr));
 }
 
 void diff_print_raw(FILE *fp, git_diff *diff)
 {
-	cl_git_pass(git_diff_print(
-		diff, GIT_DIFF_FORMAT_RAW, diff_print_cb, fp ? fp : stderr));
+	cl_git_pass(
+		git_diff_print(diff, GIT_DIFF_FORMAT_RAW,
+			git_diff_print_callback__to_file_handle, fp ? fp : stderr));
 }
diff --git a/tests/diff/iterator.c b/tests/diff/iterator.c
index 891d8a6..cdc64eb 100644
--- a/tests/diff/iterator.c
+++ b/tests/diff/iterator.c
@@ -355,6 +355,7 @@ static void index_iterator_test(
 	const char *sandbox,
 	const char *start,
 	const char *end,
+	git_iterator_flag_t flags,
 	int expected_count,
 	const char **expected_names,
 	const char **expected_oids)
@@ -362,11 +363,13 @@ static void index_iterator_test(
 	git_index *index;
 	git_iterator *i;
 	const git_index_entry *entry;
-	int error, count = 0;
+	int error, count = 0, caps;
 	git_repository *repo = cl_git_sandbox_init(sandbox);
 
 	cl_git_pass(git_repository_index(&index, repo));
-	cl_git_pass(git_iterator_for_index(&i, index, 0, start, end));
+	caps = git_index_caps(index);
+
+	cl_git_pass(git_iterator_for_index(&i, index, flags, start, end));
 
 	while (!(error = git_iterator_advance(&entry, i))) {
 		cl_assert(entry);
@@ -388,6 +391,8 @@ static void index_iterator_test(
 	cl_assert_equal_i(expected_count, count);
 
 	git_iterator_free(i);
+
+	cl_assert(caps == git_index_caps(index));
 	git_index_free(index);
 }
 
@@ -446,7 +451,8 @@ static const char *expected_index_oids_0[] = {
 void test_diff_iterator__index_0(void)
 {
 	index_iterator_test(
-		"attr", NULL, NULL, 23, expected_index_0, expected_index_oids_0);
+		"attr", NULL, NULL, 0, ARRAY_SIZE(expected_index_0),
+		expected_index_0, expected_index_oids_0);
 }
 
 static const char *expected_index_range[] = {
@@ -466,25 +472,26 @@ static const char *expected_index_oids_range[] = {
 void test_diff_iterator__index_range(void)
 {
 	index_iterator_test(
-		"attr", "root", "root", 4, expected_index_range, expected_index_oids_range);
+		"attr", "root", "root", 0, ARRAY_SIZE(expected_index_range),
+		expected_index_range, expected_index_oids_range);
 }
 
 void test_diff_iterator__index_range_empty_0(void)
 {
 	index_iterator_test(
-		"attr", "empty", "empty", 0, NULL, NULL);
+		"attr", "empty", "empty", 0, 0, NULL, NULL);
 }
 
 void test_diff_iterator__index_range_empty_1(void)
 {
 	index_iterator_test(
-		"attr", "z_empty_after", NULL, 0, NULL, NULL);
+		"attr", "z_empty_after", NULL, 0, 0, NULL, NULL);
 }
 
 void test_diff_iterator__index_range_empty_2(void)
 {
 	index_iterator_test(
-		"attr", NULL, ".aaa_empty_before", 0, NULL, NULL);
+		"attr", NULL, ".aaa_empty_before", 0, 0, NULL, NULL);
 }
 
 static const char *expected_index_1[] = {
@@ -522,9 +529,45 @@ static const char* expected_index_oids_1[] = {
 void test_diff_iterator__index_1(void)
 {
 	index_iterator_test(
-		"status", NULL, NULL, 13, expected_index_1, expected_index_oids_1);
+		"status", NULL, NULL, 0, ARRAY_SIZE(expected_index_1),
+		expected_index_1, expected_index_oids_1);
 }
 
+static const char *expected_index_cs[] = {
+	"B", "D", "F", "H", "J", "L/1", "L/B", "L/D", "L/a", "L/c",
+	"a", "c", "e", "g", "i", "k/1", "k/B", "k/D", "k/a", "k/c",
+};
+
+static const char *expected_index_ci[] = {
+	"a", "B", "c", "D", "e", "F", "g", "H", "i", "J",
+	"k/1", "k/a", "k/B", "k/c", "k/D", "L/1", "L/a", "L/B", "L/c", "L/D",
+};
+
+void test_diff_iterator__index_case_folding(void)
+{
+	git_buf path = GIT_BUF_INIT;
+	int fs_is_ci = 0;
+
+	cl_git_pass(git_buf_joinpath(&path, cl_fixture("icase"), ".gitted/CoNfIg"));
+	fs_is_ci = git_path_exists(path.ptr);
+	git_buf_free(&path);
+
+	index_iterator_test(
+		"icase", NULL, NULL, 0, ARRAY_SIZE(expected_index_cs),
+		fs_is_ci ? expected_index_ci : expected_index_cs, NULL);
+
+	cl_git_sandbox_cleanup();
+
+	index_iterator_test(
+		"icase", NULL, NULL, GIT_ITERATOR_IGNORE_CASE,
+		ARRAY_SIZE(expected_index_ci), expected_index_ci, NULL);
+
+	cl_git_sandbox_cleanup();
+
+	index_iterator_test(
+		"icase", NULL, NULL, GIT_ITERATOR_DONT_IGNORE_CASE,
+		ARRAY_SIZE(expected_index_cs), expected_index_cs, NULL);
+}
 
 /* -- WORKDIR ITERATOR TESTS -- */
 
diff --git a/tests/index/tests.c b/tests/index/tests.c
index 6e28af1..fa5c0bb 100644
--- a/tests/index/tests.c
+++ b/tests/index/tests.c
@@ -544,36 +544,22 @@ void test_index_tests__corrupted_extension(void)
 	cl_git_fail_with(git_index_open(&index, TEST_INDEXBAD_PATH), GIT_ERROR);
 }
 
-static void assert_index_is_sorted(git_index *index)
-{
-	git_vector *entries = &index->entries;
-	size_t i;
-
-	cl_assert(git_vector_is_sorted(entries));
-
-	for (i = 1; i < git_vector_length(entries); ++i) {
-		git_index_entry *prev = git_vector_get(entries, i - 1);
-		git_index_entry *curr = git_vector_get(entries, i);
-		cl_assert(index->entries._cmp(prev, curr) <= 0);
-	}
-}
-
 void test_index_tests__reload_while_ignoring_case(void)
 {
 	git_index *index;
 	unsigned int caps;
 
 	cl_git_pass(git_index_open(&index, TEST_INDEX_PATH));
-	assert_index_is_sorted(index);
+	cl_git_pass(git_vector_verify_sorted(&index->entries));
 
 	caps = git_index_caps(index);
 	cl_git_pass(git_index_set_caps(index, caps &= ~GIT_INDEXCAP_IGNORE_CASE));
 	cl_git_pass(git_index_read(index, true));
-	assert_index_is_sorted(index);
+	cl_git_pass(git_vector_verify_sorted(&index->entries));
 
 	cl_git_pass(git_index_set_caps(index, caps | GIT_INDEXCAP_IGNORE_CASE));
 	cl_git_pass(git_index_read(index, true));
-	assert_index_is_sorted(index);
+	cl_git_pass(git_vector_verify_sorted(&index->entries));
 
 	git_index_free(index);
 }
diff --git a/tests/status/ignore.c b/tests/status/ignore.c
index d6c26a8..052a8ea 100644
--- a/tests/status/ignore.c
+++ b/tests/status/ignore.c
@@ -54,8 +54,10 @@ void test_status_ignore__0(void)
 	}
 
 	/* confirm that ignore files were cached */
-	cl_assert(git_attr_cache__is_cached(g_repo, 0, ".git/info/exclude"));
-	cl_assert(git_attr_cache__is_cached(g_repo, 0, ".gitignore"));
+	cl_assert(git_attr_cache__is_cached(
+		g_repo, GIT_ATTR_FILE__FROM_FILE, ".git/info/exclude"));
+	cl_assert(git_attr_cache__is_cached(
+		g_repo, GIT_ATTR_FILE__FROM_FILE, ".gitignore"));
 }
 
 
diff --git a/tests/threads/diff.c b/tests/threads/diff.c
new file mode 100644
index 0000000..79b8580
--- /dev/null
+++ b/tests/threads/diff.c
@@ -0,0 +1,182 @@
+#include "clar_libgit2.h"
+#include "thread_helpers.h"
+
+static git_repository *_repo;
+static git_tree *_a, *_b;
+static git_atomic _counts[4];
+static int _check_counts;
+
+#define THREADS 20
+
+void test_threads_diff__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+static void setup_trees(void)
+{
+	git_index *idx;
+
+	_repo = cl_git_sandbox_reopen(); /* reopen sandbox to flush caches */
+
+	/* avoid competing to load initial index */
+	cl_git_pass(git_repository_index(&idx, _repo));
+	git_index_free(idx);
+
+	cl_git_pass(git_revparse_single(
+		(git_object **)&_a, _repo, "0017bd4ab1^{tree}"));
+	cl_git_pass(git_revparse_single(
+		(git_object **)&_b, _repo, "26a125ee1b^{tree}"));
+
+	memset(_counts, 0, sizeof(_counts));
+}
+
+static void free_trees(void)
+{
+	git_tree_free(_a); _a = NULL;
+	git_tree_free(_b); _b = NULL;
+
+	if (_check_counts) {
+		cl_assert_equal_i(288, git_atomic_get(&_counts[0]));
+		cl_assert_equal_i(112, git_atomic_get(&_counts[1]));
+		cl_assert_equal_i( 80, git_atomic_get(&_counts[2]));
+		cl_assert_equal_i( 96, git_atomic_get(&_counts[3]));
+	}
+}
+
+static void *run_index_diffs(void *arg)
+{
+	int thread = *(int *)arg;
+	git_diff_options opts = GIT_DIFF_OPTIONS_INIT;
+	git_diff *diff = NULL;
+	size_t i;
+	int exp[4] = { 0, 0, 0, 0 };
+
+	switch (thread & 0x03) {
+	case 0: /* diff index to workdir */;
+		cl_git_pass(git_diff_index_to_workdir(&diff, _repo, NULL, &opts));
+		break;
+	case 1: /* diff tree 'a' to index */;
+		cl_git_pass(git_diff_tree_to_index(&diff, _repo, _a, NULL, &opts));
+		break;
+	case 2: /* diff tree 'b' to index */;
+		cl_git_pass(git_diff_tree_to_index(&diff, _repo, _b, NULL, &opts));
+		break;
+	case 3: /* diff index to workdir (explicit index) */;
+		{
+			git_index *idx;
+			cl_git_pass(git_repository_index(&idx, _repo));
+			cl_git_pass(git_diff_index_to_workdir(&diff, _repo, idx, &opts));
+			git_index_free(idx);
+			break;
+		}
+	}
+
+	/* keep some diff stats to make sure results are as expected */
+
+	i = git_diff_num_deltas(diff);
+	git_atomic_add(&_counts[0], (int32_t)i);
+	exp[0] = (int)i;
+
+	while (i > 0) {
+		switch (git_diff_get_delta(diff, --i)->status) {
+		case GIT_DELTA_MODIFIED: exp[1]++; git_atomic_inc(&_counts[1]); break;
+		case GIT_DELTA_ADDED:    exp[2]++; git_atomic_inc(&_counts[2]); break;
+		case GIT_DELTA_DELETED:  exp[3]++; git_atomic_inc(&_counts[3]); break;
+		default: break;
+		}
+	}
+
+	switch (thread & 0x03) {
+	case 0: case 3:
+		cl_assert_equal_i(8, exp[0]); cl_assert_equal_i(4, exp[1]);
+		cl_assert_equal_i(0, exp[2]); cl_assert_equal_i(4, exp[3]);
+		break;
+	case 1:
+		cl_assert_equal_i(12, exp[0]); cl_assert_equal_i(3, exp[1]);
+		cl_assert_equal_i(7, exp[2]); cl_assert_equal_i(2, exp[3]);
+		break;
+	case 2:
+		cl_assert_equal_i(8, exp[0]); cl_assert_equal_i(3, exp[1]);
+		cl_assert_equal_i(3, exp[2]); cl_assert_equal_i(2, exp[3]);
+		break;
+	}
+
+	git_diff_free(diff);
+	giterr_clear();
+
+	return arg;
+}
+
+void test_threads_diff__concurrent_diffs(void)
+{
+	_repo = cl_git_sandbox_init("status");
+	_check_counts = 1;
+
+	run_in_parallel(
+		5, 32, run_index_diffs, setup_trees, free_trees);
+}
+
+static void *run_index_diffs_with_modifier(void *arg)
+{
+	int thread = *(int *)arg;
+	git_diff_options opts = GIT_DIFF_OPTIONS_INIT;
+	git_diff *diff = NULL;
+	git_index *idx = NULL;
+
+	cl_git_pass(git_repository_index(&idx, _repo));
+
+	/* have first thread altering the index as we go */
+	if (thread == 0) {
+		int i;
+
+		for (i = 0; i < 300; ++i) {
+			switch (i & 0x03) {
+			case 0: (void)git_index_add_bypath(idx, "new_file"); break;
+			case 1: (void)git_index_remove_bypath(idx, "modified_file"); break;
+			case 2: (void)git_index_remove_bypath(idx, "new_file"); break;
+			case 3: (void)git_index_add_bypath(idx, "modified_file"); break;
+			}
+			git_thread_yield();
+		}
+
+		goto done;
+	}
+
+	/* only use explicit index in this test to prevent reloading */
+
+	switch (thread & 0x03) {
+	case 0: /* diff index to workdir */;
+		cl_git_pass(git_diff_index_to_workdir(&diff, _repo, idx, &opts));
+		break;
+	case 1: /* diff tree 'a' to index */;
+		cl_git_pass(git_diff_tree_to_index(&diff, _repo, _a, idx, &opts));
+		break;
+	case 2: /* diff tree 'b' to index */;
+		cl_git_pass(git_diff_tree_to_index(&diff, _repo, _b, idx, &opts));
+		break;
+	case 3: /* diff index to workdir reversed */;
+		opts.flags |= GIT_DIFF_REVERSE;
+		cl_git_pass(git_diff_index_to_workdir(&diff, _repo, idx, &opts));
+		break;
+	}
+
+	/* results will be unpredictable with index modifier thread running */
+
+	git_diff_free(diff);
+
+done:
+	git_index_free(idx);
+	giterr_clear();
+
+	return arg;
+}
+
+void test_threads_diff__with_concurrent_index_modified(void)
+{
+	_repo = cl_git_sandbox_init("status");
+	_check_counts = 0;
+
+	run_in_parallel(
+		5, 16, run_index_diffs_with_modifier, setup_trees, free_trees);
+}
diff --git a/tests/threads/iterator.c b/tests/threads/iterator.c
new file mode 100644
index 0000000..8aeae1a
--- /dev/null
+++ b/tests/threads/iterator.c
@@ -0,0 +1,49 @@
+#include "clar_libgit2.h"
+#include "thread_helpers.h"
+#include "iterator.h"
+
+static git_repository *_repo;
+
+void test_threads_iterator__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+static void *run_workdir_iterator(void *arg)
+{
+	int error = 0;
+	git_iterator *iter;
+	const git_index_entry *entry = NULL;
+
+	cl_git_pass(git_iterator_for_workdir(
+		&iter, _repo, GIT_ITERATOR_DONT_AUTOEXPAND, NULL, NULL));
+
+	while (!error) {
+		if (entry && entry->mode == GIT_FILEMODE_TREE) {
+			error = git_iterator_advance_into(&entry, iter);
+
+			if (error == GIT_ENOTFOUND)
+				error = git_iterator_advance(&entry, iter);
+		} else {
+			error = git_iterator_advance(&entry, iter);
+		}
+
+		if (!error)
+			(void)git_iterator_current_is_ignored(iter);
+	}
+
+	cl_assert_equal_i(GIT_ITEROVER, error);
+
+	git_iterator_free(iter);
+	giterr_clear();
+	return arg;
+}
+
+
+void test_threads_iterator__workdir(void)
+{
+	_repo = cl_git_sandbox_init("status");
+
+	run_in_parallel(
+		1, 20, run_workdir_iterator, NULL, NULL);
+}
diff --git a/tests/threads/refdb.c b/tests/threads/refdb.c
index fbf6ac0..3b35b45 100644
--- a/tests/threads/refdb.c
+++ b/tests/threads/refdb.c
@@ -37,6 +37,7 @@ static void *iterate_refs(void *arg)
 
 	git_reference_iterator_free(i);
 
+	giterr_clear();
 	return arg;
 }
 
@@ -115,6 +116,7 @@ static void *create_refs(void *arg)
 	for (i = 0; i < 10; ++i)
 		git_reference_free(ref[i]);
 
+	giterr_clear();
 	return arg;
 }
 
@@ -141,6 +143,7 @@ static void *delete_refs(void *arg)
 		}
 	}
 
+	giterr_clear();
 	return arg;
 }
 
diff --git a/tests/threads/thread_helpers.c b/tests/threads/thread_helpers.c
new file mode 100644
index 0000000..25370dd
--- /dev/null
+++ b/tests/threads/thread_helpers.c
@@ -0,0 +1,44 @@
+#include "clar_libgit2.h"
+#include "thread_helpers.h"
+
+void run_in_parallel(
+	int repeats,
+	int threads,
+	void *(*func)(void *),
+	void (*before_test)(void),
+	void (*after_test)(void))
+{
+	int r, t, *id = git__calloc(threads, sizeof(int));
+#ifdef GIT_THREADS
+	git_thread *th = git__calloc(threads, sizeof(git_thread));
+	cl_assert(th != NULL);
+#else
+	void *th = NULL;
+#endif
+
+	cl_assert(id != NULL);
+
+	for (r = 0; r < repeats; ++r) {
+		if (before_test) before_test();
+
+		for (t = 0; t < threads; ++t) {
+			id[t] = t;
+#ifdef GIT_THREADS
+			cl_git_pass(git_thread_create(&th[t], NULL, func, &id[t]));
+#else
+			cl_assert(func(&id[t]) == &id[t]);
+#endif
+		}
+
+#ifdef GIT_THREADS
+		for (t = 0; t < threads; ++t)
+			cl_git_pass(git_thread_join(th[t], NULL));
+		memset(th, 0, threads * sizeof(git_thread));
+#endif
+
+		if (after_test) after_test();
+	}
+
+	git__free(id);
+	git__free(th);
+}
diff --git a/tests/threads/thread_helpers.h b/tests/threads/thread_helpers.h
new file mode 100644
index 0000000..3c13cfb
--- /dev/null
+++ b/tests/threads/thread_helpers.h
@@ -0,0 +1,8 @@
+#include "thread-utils.h"
+
+void run_in_parallel(
+	int repeats,
+	int threads,
+	void *(*func)(void *),
+	void (*before_test)(void),
+	void (*after_test)(void));