thodg/libgit2

diff --git a/src/attr.c b/src/attr.c
index a021726..2e1ef7c 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -29,6 +29,7 @@ git_attr_t git_attr_value(const char *attr)
 
 static int collect_attr_files(
 	git_repository *repo,
+	git_attr_session *attr_session,
 	uint32_t flags,
 	const char *path,
 	git_vector *files);
@@ -57,7 +58,7 @@ int git_attr_get(
 	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, NULL, flags, pathname, &files)) < 0)
 		goto cleanup;
 
 	memset(&attr, 0, sizeof(attr));
@@ -90,9 +91,10 @@ typedef struct {
 	git_attr_assignment *found;
 } attr_get_many_info;
 
-int git_attr_get_many(
+int git_attr_get_many_with_session(
 	const char **values,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	uint32_t flags,
 	const char *pathname,
 	size_t num_attr,
@@ -115,7 +117,7 @@ int git_attr_get_many(
 	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, attr_session, flags, pathname, &files)) < 0)
 		goto cleanup;
 
 	info = git__calloc(num_attr, sizeof(attr_get_many_info));
@@ -161,6 +163,17 @@ cleanup:
 	return error;
 }
 
+int git_attr_get_many(
+	const char **values,
+	git_repository *repo,
+	uint32_t flags,
+	const char *pathname,
+	size_t num_attr,
+	const char **names)
+{
+	return git_attr_get_many_with_session(
+		values, repo, NULL, flags, pathname, num_attr, names);
+}
 
 int git_attr_foreach(
 	git_repository *repo,
@@ -183,7 +196,7 @@ 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, NULL, flags, pathname, &files)) < 0 ||
 		(error = git_strmap_alloc(&seen)) < 0)
 		goto cleanup;
 
@@ -219,6 +232,7 @@ cleanup:
 
 static int preload_attr_file(
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_attr_file_source source,
 	const char *base,
 	const char *file)
@@ -229,19 +243,61 @@ static int preload_attr_file(
 	if (!file)
 		return 0;
 	if (!(error = git_attr_cache__get(
-			&preload, repo, source, base, file, git_attr_file__parse_buffer)))
+			&preload, repo, attr_session, source, base, file, git_attr_file__parse_buffer)))
 		git_attr_file__free(preload);
 
 	return error;
 }
 
-static int attr_setup(git_repository *repo)
+static int system_attr_file(
+	git_buf *out,
+	git_attr_session *attr_session)
+{
+	int error;
+
+	if (!attr_session) {
+		error = git_sysdir_find_system_file(out, GIT_ATTR_FILE_SYSTEM);
+
+		if (error == GIT_ENOTFOUND)
+			giterr_clear();
+
+		return error;
+	}
+
+	if (!attr_session->init_sysdir) {
+		error = git_sysdir_find_system_file(&attr_session->sysdir, GIT_ATTR_FILE_SYSTEM);
+
+		if (error == GIT_ENOTFOUND)
+			giterr_clear();
+		else if (error)
+			return error;
+
+		attr_session->init_sysdir = 1;
+	}
+
+	if (attr_session->sysdir.size == 0)
+		return GIT_ENOTFOUND;
+
+	/* We can safely provide a git_buf with no allocation (asize == 0) to
+	 * a consumer. This allows them to treat this as a regular `git_buf`,
+	 * but their call to `git_buf_free` will not attempt to free it.
+	 */
+	out->ptr = attr_session->sysdir.ptr;
+	out->size = attr_session->sysdir.size;
+	out->asize = 0;
+	return 0;
+}
+
+static int attr_setup(git_repository *repo, git_attr_session *attr_session)
 {
 	int error = 0;
 	const char *workdir = git_repository_workdir(repo);
 	git_index *idx = NULL;
 	git_buf sys = GIT_BUF_INIT;
 
+	if (attr_session && attr_session->init_setup)
+		return 0;
+
 	if ((error = git_attr_cache__init(repo)) < 0)
 		return error;
 
@@ -249,39 +305,39 @@ static int attr_setup(git_repository *repo)
 	 * definitions will be available for later file parsing
 	 */
 
-	if (!(error = git_sysdir_find_system_file(&sys, GIT_ATTR_FILE_SYSTEM))) {
+	error = system_attr_file(&sys, attr_session);
+
+	if (error == 0)
 		error = preload_attr_file(
-			repo, GIT_ATTR_FILE__FROM_FILE, NULL, sys.ptr);
-		git_buf_free(&sys);
-	}
-	if (error < 0) {
-		if (error == GIT_ENOTFOUND) {
-			giterr_clear();
-			error = 0;
-		} else
-			return error;
-	}
+			repo, attr_session, GIT_ATTR_FILE__FROM_FILE, NULL, sys.ptr);
+	else if (error != GIT_ENOTFOUND)
+		return error;
+
+	git_buf_free(&sys);
 
 	if ((error = preload_attr_file(
-			repo, GIT_ATTR_FILE__FROM_FILE,
+			repo, attr_session, GIT_ATTR_FILE__FROM_FILE,
 			NULL, git_repository_attr_cache(repo)->cfg_attr_file)) < 0)
 		return error;
 
 	if ((error = preload_attr_file(
-			repo, GIT_ATTR_FILE__FROM_FILE,
+			repo, attr_session, GIT_ATTR_FILE__FROM_FILE,
 			git_repository_path(repo), GIT_ATTR_FILE_INREPO)) < 0)
 		return error;
 
 	if (workdir != NULL &&
 		(error = preload_attr_file(
-			repo, GIT_ATTR_FILE__FROM_FILE, workdir, GIT_ATTR_FILE)) < 0)
+			repo, attr_session, GIT_ATTR_FILE__FROM_FILE, workdir, GIT_ATTR_FILE)) < 0)
 		return error;
 
 	if ((error = git_repository_index__weakptr(&idx, repo)) < 0 ||
 		(error = preload_attr_file(
-			repo, GIT_ATTR_FILE__FROM_INDEX, NULL, GIT_ATTR_FILE)) < 0)
+			repo, attr_session, GIT_ATTR_FILE__FROM_INDEX, NULL, GIT_ATTR_FILE)) < 0)
 		return error;
 
+	if (attr_session)
+		attr_session->init_setup = 1;
+
 	return error;
 }
 
@@ -321,6 +377,7 @@ int git_attr_add_macro(
 
 typedef struct {
 	git_repository *repo;
+	git_attr_session *attr_session;
 	uint32_t flags;
 	const char *workdir;
 	git_index *index;
@@ -356,6 +413,7 @@ static int attr_decide_sources(
 
 static int push_attr_file(
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_vector *list,
 	git_attr_file_source source,
 	const char *base,
@@ -364,8 +422,9 @@ static int push_attr_file(
 	int error = 0;
 	git_attr_file *file = NULL;
 
-	error = git_attr_cache__get(
-		&file, repo, source, base, filename, git_attr_file__parse_buffer);
+	error = git_attr_cache__get(&file, repo, attr_session,
+		source, base, filename, git_attr_file__parse_buffer);
+
 	if (error < 0)
 		return error;
 
@@ -387,8 +446,8 @@ static int push_one_attr(void *ref, const char *path)
 		info->flags, info->workdir != NULL, info->index != NULL, src);
 
 	for (i = 0; !error && i < n_src; ++i)
-		error = push_attr_file(
-			info->repo, info->files, src[i], path, GIT_ATTR_FILE);
+		error = push_attr_file(info->repo, info->attr_session,
+			info->files, src[i], path, GIT_ATTR_FILE);
 
 	return error;
 }
@@ -407,6 +466,7 @@ static void release_attr_files(git_vector *files)
 
 static int collect_attr_files(
 	git_repository *repo,
+	git_attr_session *attr_session,
 	uint32_t flags,
 	const char *path,
 	git_vector *files)
@@ -416,7 +476,7 @@ static int collect_attr_files(
 	const char *workdir = git_repository_workdir(repo);
 	attr_walk_up_info info = { NULL };
 
-	if ((error = attr_setup(repo)) < 0)
+	if ((error = attr_setup(repo, attr_session)) < 0)
 		return error;
 
 	/* Resolve path in a non-bare repo */
@@ -435,12 +495,13 @@ static int collect_attr_files(
 	 */
 
 	error = push_attr_file(
-		repo, files, GIT_ATTR_FILE__FROM_FILE,
+		repo, attr_session, files, GIT_ATTR_FILE__FROM_FILE,
 		git_repository_path(repo), GIT_ATTR_FILE_INREPO);
 	if (error < 0)
 		goto cleanup;
 
-	info.repo  = repo;
+	info.repo = repo;
+	info.attr_session = attr_session;
 	info.flags = flags;
 	info.workdir = workdir;
 	if (git_repository_index__weakptr(&info.index, repo) < 0)
@@ -457,21 +518,21 @@ static int collect_attr_files(
 
 	if (git_repository_attr_cache(repo)->cfg_attr_file != NULL) {
 		error = push_attr_file(
-			repo, files, GIT_ATTR_FILE__FROM_FILE,
+			repo, attr_session, files, GIT_ATTR_FILE__FROM_FILE,
 			NULL, git_repository_attr_cache(repo)->cfg_attr_file);
 		if (error < 0)
 			goto cleanup;
 	}
 
 	if ((flags & GIT_ATTR_CHECK_NO_SYSTEM) == 0) {
-		error = git_sysdir_find_system_file(&dir, GIT_ATTR_FILE_SYSTEM);
+		error = system_attr_file(&dir, attr_session);
+
 		if (!error)
 			error = push_attr_file(
-				repo, files, GIT_ATTR_FILE__FROM_FILE, NULL, dir.ptr);
-		else if (error == GIT_ENOTFOUND) {
-			giterr_clear();
+				repo, attr_session, files, GIT_ATTR_FILE__FROM_FILE,
+				NULL, dir.ptr);
+		else if (error == GIT_ENOTFOUND)
 			error = 0;
-		}
 	}
 
  cleanup:
diff --git a/src/attr_file.c b/src/attr_file.c
index 5b008b0..8997946 100644
--- a/src/attr_file.c
+++ b/src/attr_file.c
@@ -96,6 +96,7 @@ static int attr_file_oid_from_index(
 int git_attr_file__load(
 	git_attr_file **out,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_attr_file_entry *entry,
 	git_attr_file_source source,
 	git_attr_file_parser parser)
@@ -105,6 +106,7 @@ int git_attr_file__load(
 	git_buf content = GIT_BUF_INIT;
 	git_attr_file *file;
 	struct stat st;
+	bool nonexistent = false;
 
 	*out = NULL;
 
@@ -127,22 +129,16 @@ int git_attr_file__load(
 	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 */
+		/* For open or read errors, pretend that we got ENOTFOUND. */
 		/* 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);
-
-		if (error < 0)
-			return GIT_ENOTFOUND;
+		if (p_stat(entry->fullpath, &st) < 0 ||
+			S_ISDIR(st.st_mode) ||
+			(fd = git_futils_open_ro(entry->fullpath)) < 0 ||
+			(error = git_futils_readbuffer_fd(&content, fd, (size_t)st.st_size)) < 0)
+			nonexistent = true;
+		else
+			p_close(fd);
 
 		break;
 	}
@@ -154,13 +150,21 @@ int git_attr_file__load(
 	if ((error = git_attr_file__new(&file, entry, source)) < 0)
 		goto cleanup;
 
+	/* store the key of the attr_reader; don't bother with cache
+	 * invalidation during the same attr reader session.
+	 */
+	if (attr_session)
+		file->session_key = attr_session->key;
+
 	if (parser && (error = parser(repo, file, git_buf_cstr(&content))) < 0) {
 		git_attr_file__free(file);
 		goto cleanup;
 	}
 
-	/* write cache breaker */
-	if (source == GIT_ATTR_FILE__FROM_INDEX)
+	/* write cache breakers */
+	if (nonexistent)
+		file->nonexistent = 1;
+	else 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);
@@ -175,11 +179,22 @@ cleanup:
 	return error;
 }
 
-int git_attr_file__out_of_date(git_repository *repo, git_attr_file *file)
+int git_attr_file__out_of_date(
+	git_repository *repo,
+	git_attr_session *attr_session,
+	git_attr_file *file)
 {
 	if (!file)
 		return 1;
 
+	/* we are never out of date if we just created this data in the same
+	 * attr_session; otherwise, nonexistent files must be invalidated
+	 */
+	if (attr_session && attr_session->key == file->session_key)
+		return 0;
+	else if (file->nonexistent)
+		return 1;
+
 	switch (file->source) {
 	case GIT_ATTR_FILE__IN_MEMORY:
 		return 0;
@@ -831,3 +846,22 @@ void git_attr_rule__free(git_attr_rule *rule)
 	git__free(rule);
 }
 
+int git_attr_session__init(git_attr_session *session, git_repository *repo)
+{
+	assert(repo);
+
+	session->key = git_atomic_inc(&repo->attr_session_key);
+
+	return 0;
+}
+
+void git_attr_session__free(git_attr_session *session)
+{
+	if (!session)
+		return;
+
+	git_buf_free(&session->sysdir);
+	git_buf_free(&session->tmp);
+
+	memset(session, 0, sizeof(git_attr_session));
+}
diff --git a/src/attr_file.h b/src/attr_file.h
index 93de84d..aa9a16d 100644
--- a/src/attr_file.h
+++ b/src/attr_file.h
@@ -38,11 +38,11 @@
 	 GIT_ATTR_FNMATCH_ALLOWMACRO | GIT_ATTR_FNMATCH_NOLEADINGDIR)
 
 typedef enum {
-	GIT_ATTR_FILE__IN_MEMORY  = 0,
-	GIT_ATTR_FILE__FROM_FILE  = 1,
-	GIT_ATTR_FILE__FROM_INDEX = 2,
+	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_NUM_SOURCES  = 3
 } git_attr_file_source;
 
 extern const char *git_attr__true;
@@ -84,6 +84,8 @@ typedef struct {
 	git_attr_file_source source;
 	git_vector rules;			/* vector of <rule*> or <fnmatch*> */
 	git_pool pool;
+	unsigned int nonexistent:1;
+	int session_key;
 	union {
 		git_oid oid;
 		git_futils_filestamp stamp;
@@ -96,11 +98,6 @@ struct git_attr_file_entry {
 	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;
@@ -108,6 +105,35 @@ typedef struct {
 	int      is_dir;
 } git_attr_path;
 
+/* A git_attr_session can provide an "instance" of reading, to prevent cache
+ * invalidation during a single operation instance (like checkout).
+ */
+
+typedef struct {
+	int key;
+	unsigned int init_setup:1,
+		init_sysdir:1;
+	git_buf sysdir;
+	git_buf tmp;
+} git_attr_session;
+
+extern int git_attr_session__init(git_attr_session *attr_session, git_repository *repo);
+extern void git_attr_session__free(git_attr_session *session);
+
+extern int git_attr_get_many_with_session(
+	const char **values_out,
+	git_repository *repo,
+	git_attr_session *attr_session,
+	uint32_t flags,
+	const char *path,
+	size_t num_attr,
+	const char **names);
+
+typedef int (*git_attr_file_parser)(
+	git_repository *repo,
+	git_attr_file *file,
+	const char *data);
+
 /*
  * git_attr_file API
  */
@@ -122,6 +148,7 @@ void git_attr_file__free(git_attr_file *file);
 int git_attr_file__load(
 	git_attr_file **out,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_attr_file_entry *ce,
 	git_attr_file_source source,
 	git_attr_file_parser parser);
@@ -130,7 +157,7 @@ int git_attr_file__load_standalone(
 	git_attr_file **out, const char *path);
 
 int git_attr_file__out_of_date(
-	git_repository *repo, git_attr_file *file);
+	git_repository *repo, git_attr_session *session, git_attr_file *file);
 
 int git_attr_file__parse_buffer(
 	git_repository *repo, git_attr_file *attrs, const char *data);
diff --git a/src/attrcache.c b/src/attrcache.c
index b4579bf..9a9b9d0 100644
--- a/src/attrcache.c
+++ b/src/attrcache.c
@@ -149,6 +149,7 @@ static int attr_cache_lookup(
 	git_attr_file **out_file,
 	git_attr_file_entry **out_entry,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_attr_file_source source,
 	const char *base,
 	const char *filename)
@@ -162,9 +163,12 @@ static int attr_cache_lookup(
 
 	/* join base and path as needed */
 	if (base != NULL && git_path_root(filename) < 0) {
-		if (git_buf_joinpath(&path, base, filename) < 0)
+		git_buf *p = attr_session ? &attr_session->tmp : &path;
+
+		if (git_buf_joinpath(p, base, filename) < 0)
 			return -1;
-		filename = path.ptr;
+
+		filename = p->ptr;
 	}
 
 	relfile = filename;
@@ -196,6 +200,7 @@ cleanup:
 int git_attr_cache__get(
 	git_attr_file **out,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_attr_file_source source,
 	const char *base,
 	const char *filename,
@@ -207,12 +212,12 @@ int git_attr_cache__get(
 	git_attr_file *file = NULL, *updated = NULL;
 
 	if ((error = attr_cache_lookup(
-			&file, &entry, repo, source, base, filename)) < 0)
+			&file, &entry, repo, attr_session, 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 (!file || (error = git_attr_file__out_of_date(repo, attr_session, file)) > 0)
+		error = git_attr_file__load(&updated, repo, attr_session, entry, source, parser);
 
 	/* if we loaded the file, insert into and/or update cache */
 	if (updated) {
diff --git a/src/attrcache.h b/src/attrcache.h
index be0a22f..44e1ffd 100644
--- a/src/attrcache.h
+++ b/src/attrcache.h
@@ -31,6 +31,7 @@ extern int git_attr_cache__do_init(git_repository *repo);
 extern int git_attr_cache__get(
 	git_attr_file **file,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_attr_file_source source,
 	const char *base,
 	const char *filename,
diff --git a/src/checkout.c b/src/checkout.c
index 52a076d..3f65a9e 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -28,6 +28,11 @@
 #include "buf_text.h"
 #include "merge_file.h"
 #include "path.h"
+#include "attr.h"
+#include "pool.h"
+#include "strmap.h"
+
+GIT__USE_STRMAP;
 
 /* See docs/checkout-internals.md for more information */
 
@@ -68,7 +73,8 @@ typedef struct {
 	size_t total_steps;
 	size_t completed_steps;
 	git_checkout_perfdata perfdata;
-	git_buf last_mkdir;
+	git_strmap *mkdir_map;
+	git_attr_session attr_session;
 } checkout_data;
 
 typedef struct {
@@ -1291,25 +1297,6 @@ fail:
 	return error;
 }
 
-static int checkout_mkdir(
-	checkout_data *data,
-	const char *path,
-	const char *base,
-	mode_t mode,
-	unsigned int flags)
-{
-	struct git_futils_mkdir_perfdata mkdir_perfdata = {0};
-
-	int error = git_futils_mkdir_withperf(
-		path, base, mode, flags, &mkdir_perfdata);
-
-	data->perfdata.mkdir_calls += mkdir_perfdata.mkdir_calls;
-	data->perfdata.stat_calls += mkdir_perfdata.stat_calls;
-	data->perfdata.chmod_calls += mkdir_perfdata.chmod_calls;
-
-	return error;
-}
-
 static bool should_remove_existing(checkout_data *data)
 {
 	int ignorecase = 0;
@@ -1325,31 +1312,43 @@ static bool should_remove_existing(checkout_data *data)
 #define MKDIR_REMOVE_EXISTING \
 	MKDIR_NORMAL | GIT_MKDIR_REMOVE_FILES | GIT_MKDIR_REMOVE_SYMLINKS
 
+static int checkout_mkdir(
+	checkout_data *data,
+	const char *path,
+	const char *base,
+	mode_t mode,
+	unsigned int flags)
+{
+	struct git_futils_mkdir_options mkdir_opts = {0};
+	int error;
+
+	mkdir_opts.dir_map = data->mkdir_map;
+	mkdir_opts.pool = &data->pool;
+
+	error = git_futils_mkdir_ext(
+		path, base, mode, flags, &mkdir_opts);
+
+	data->perfdata.mkdir_calls += mkdir_opts.perfdata.mkdir_calls;
+	data->perfdata.stat_calls += mkdir_opts.perfdata.stat_calls;
+	data->perfdata.chmod_calls += mkdir_opts.perfdata.chmod_calls;
+
+	return error;
+}
+
 static int mkpath2file(
 	checkout_data *data, const char *path, unsigned int mode)
 {
-	git_buf *mkdir_path = &data->tmp;
 	struct stat st;
 	bool remove_existing = should_remove_existing(data);
+	unsigned int flags =
+		(remove_existing ? MKDIR_REMOVE_EXISTING : MKDIR_NORMAL) |
+		GIT_MKDIR_SKIP_LAST;
 	int error;
 
-	if ((error = git_buf_sets(mkdir_path, path)) < 0)
+	if ((error = checkout_mkdir(
+			data, path, data->opts.target_directory, mode, flags)) < 0)
 		return error;
 
-	git_buf_rtruncate_at_char(mkdir_path, '/');
-
-	if (!data->last_mkdir.size ||
-		data->last_mkdir.size != mkdir_path->size ||
-		memcmp(mkdir_path->ptr, data->last_mkdir.ptr, mkdir_path->size) != 0) {
-
-		if ((error = checkout_mkdir(
-				data, mkdir_path->ptr, data->opts.target_directory, mode,
-				remove_existing ? MKDIR_REMOVE_EXISTING : MKDIR_NORMAL)) < 0)
-			return error;
-
-		git_buf_swap(&data->last_mkdir, mkdir_path);
-	}
-
 	if (remove_existing) {
 		data->perfdata.stat_calls++;
 
@@ -1425,8 +1424,8 @@ static int blob_content_to_file(
 		hint_path = path;
 
 	if (!data->opts.disable_filters)
-		error = git_filter_list_load(
-			&fl, git_blob_owner(blob), blob, hint_path,
+		error = git_filter_list__load_with_attr_session(
+			&fl, data->repo, &data->attr_session, blob, hint_path,
 			GIT_FILTER_TO_WORKTREE, GIT_FILTER_OPT_DEFAULT);
 
 	if (!error)
@@ -2008,7 +2007,8 @@ static int checkout_write_merge(
 		in_data.ptr = (char *)result.ptr;
 		in_data.size = result.len;
 
-		if ((error = git_filter_list_load(&fl, data->repo, NULL, git_buf_cstr(&path_workdir),
+		if ((error = git_filter_list__load_with_attr_session(
+				&fl, data->repo, &data->attr_session, NULL, git_buf_cstr(&path_workdir),
 				GIT_FILTER_TO_WORKTREE, GIT_FILTER_OPT_DEFAULT)) < 0 ||
 			(error = git_filter_list_apply_to_data(&out_data, fl, &in_data)) < 0)
 			goto done;
@@ -2212,12 +2212,17 @@ static void checkout_data_clear(checkout_data *data)
 	git__free(data->pfx);
 	data->pfx = NULL;
 
-	git_buf_free(&data->last_mkdir);
+	git_strmap_free(data->mkdir_map);
+
 	git_buf_free(&data->path);
 	git_buf_free(&data->tmp);
 
 	git_index_free(data->index);
 	data->index = NULL;
+
+	git_strmap_free(data->mkdir_map);
+
+	git_attr_session__free(&data->attr_session);
 }
 
 static int checkout_data_init(
@@ -2355,11 +2360,14 @@ static int checkout_data_init(
 		(error = git_vector_init(&data->update_conflicts, 0, NULL)) < 0 ||
 		(error = git_pool_init(&data->pool, 1, 0)) < 0 ||
 		(error = git_buf_puts(&data->path, data->opts.target_directory)) < 0 ||
-		(error = git_path_to_dir(&data->path)) < 0)
+		(error = git_path_to_dir(&data->path)) < 0 ||
+		(error = git_strmap_alloc(&data->mkdir_map)) < 0)
 		goto cleanup;
 
 	data->workdir_len = git_buf_len(&data->path);
 
+	git_attr_session__init(&data->attr_session, data->repo);
+
 cleanup:
 	if (error < 0)
 		checkout_data_clear(data);
diff --git a/src/fileops.c b/src/fileops.c
index 4a62d21..eddd5a8 100644
--- a/src/fileops.c
+++ b/src/fileops.c
@@ -7,11 +7,14 @@
 #include "common.h"
 #include "fileops.h"
 #include "global.h"
+#include "strmap.h"
 #include <ctype.h>
 #if GIT_WIN32
 #include "win32/findfile.h"
 #endif
 
+GIT__USE_STRMAP;
+
 int git_futils_mkpath2file(const char *file_path, const mode_t mode)
 {
 	return git_futils_mkdir(
@@ -321,12 +324,12 @@ GIT_INLINE(int) validate_existing(
 	return 0;
 }
 
-int git_futils_mkdir_withperf(
+int git_futils_mkdir_ext(
 	const char *path,
 	const char *base,
 	mode_t mode,
 	uint32_t flags,
-	struct git_futils_mkdir_perfdata *perfdata)
+	struct git_futils_mkdir_options *opts)
 {
 	int error = -1;
 	git_buf make_path = GIT_BUF_INIT;
@@ -401,11 +404,14 @@ int git_futils_mkdir_withperf(
 		*tail = '\0';
 		st.st_mode = 0;
 
+		if (opts->dir_map && git_strmap_exists(opts->dir_map, make_path.ptr))
+			continue;
+
 		/* See what's going on with this path component */
-		perfdata->stat_calls++;
+		opts->perfdata.stat_calls++;
 
 		if (p_lstat(make_path.ptr, &st) < 0) {
-			perfdata->mkdir_calls++;
+			opts->perfdata.mkdir_calls++;
 
 			if (errno != ENOENT || p_mkdir(make_path.ptr, mode) < 0) {
 				giterr_set(GITERR_OS, "Failed to make directory '%s'", make_path.ptr);
@@ -423,7 +429,7 @@ int git_futils_mkdir_withperf(
 			}
 
 			if ((error = validate_existing(
-				make_path.ptr, &st, mode, flags, perfdata)) < 0)
+				make_path.ptr, &st, mode, flags, &opts->perfdata)) < 0)
 					goto done;
 		}
 
@@ -432,7 +438,7 @@ int git_futils_mkdir_withperf(
 			 (lastch == '\0' && (flags & GIT_MKDIR_CHMOD) != 0)) &&
 			st.st_mode != mode) {
 
-			perfdata->chmod_calls++;
+			opts->perfdata.chmod_calls++;
 
 			if ((error = p_chmod(make_path.ptr, mode)) < 0 &&
 				lastch == '\0') {
@@ -441,6 +447,17 @@ int git_futils_mkdir_withperf(
 				goto done;
 			}
 		}
+
+		if (opts->dir_map && opts->pool) {
+			char *cache_path = git_pool_malloc(opts->pool, make_path.size + 1);
+			GITERR_CHECK_ALLOC(cache_path);
+
+			memcpy(cache_path, make_path.ptr, make_path.size + 1);
+
+			git_strmap_insert(opts->dir_map, cache_path, cache_path, error);
+			if (error < 0)
+				goto done;
+		}
 	}
 
 	error = 0;
@@ -448,7 +465,7 @@ int git_futils_mkdir_withperf(
 	/* check that full path really is a directory if requested & needed */
 	if ((flags & GIT_MKDIR_VERIFY_DIR) != 0 &&
 		lastch != '\0') {
-		perfdata->stat_calls++;
+		opts->perfdata.stat_calls++;
 
 		if (p_stat(make_path.ptr, &st) < 0 || !S_ISDIR(st.st_mode)) {
 			giterr_set(GITERR_OS, "Path is not a directory '%s'",
@@ -468,8 +485,8 @@ int git_futils_mkdir(
 	mode_t mode,
 	uint32_t flags)
 {
-	struct git_futils_mkdir_perfdata perfdata = {0};
-	return git_futils_mkdir_withperf(path, base, mode, flags, &perfdata);
+	struct git_futils_mkdir_options options = {0};
+	return git_futils_mkdir_ext(path, base, mode, flags, &options);
 }
 
 int git_futils_mkdir_r(const char *path, const char *base, const mode_t mode)
diff --git a/src/fileops.h b/src/fileops.h
index 4aaf178..0f6466c 100644
--- a/src/fileops.h
+++ b/src/fileops.h
@@ -11,6 +11,8 @@
 #include "map.h"
 #include "posix.h"
 #include "path.h"
+#include "pool.h"
+#include "strmap.h"
 
 /**
  * Filebuffer methods
@@ -95,6 +97,13 @@ struct git_futils_mkdir_perfdata
 	size_t chmod_calls;
 };
 
+struct git_futils_mkdir_options
+{
+	git_strmap *dir_map;
+	git_pool *pool;
+	struct git_futils_mkdir_perfdata perfdata;
+};
+
 /**
  * Create a directory or entire path.
  *
@@ -106,10 +115,10 @@ struct git_futils_mkdir_perfdata
  * @param base Root for relative path.  These directories will never be made.
  * @param mode The mode to use for created directories.
  * @param flags Combination of the mkdir flags above.
- * @param perfdata Performance data, use `git_futils_mkdir` if you don't want this data.
+ * @param opts Extended options, use `git_futils_mkdir` if you are not interested.
  * @return 0 on success, else error code
  */
-extern int git_futils_mkdir_withperf(const char *path, const char *base, mode_t mode, uint32_t flags, struct git_futils_mkdir_perfdata *perfdata);
+extern int git_futils_mkdir_ext(const char *path, const char *base, mode_t mode, uint32_t flags, struct git_futils_mkdir_options *opts);
 
 /**
  * Create a directory or entire path.  Similar to `git_futils_mkdir_withperf`
diff --git a/src/filter.c b/src/filter.c
index b5a8bdd..22eaf51 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -394,15 +394,19 @@ static int filter_list_new(
 }
 
 static int filter_list_check_attributes(
-	const char ***out, git_filter_def *fdef, const git_filter_source *src)
+	const char ***out,
+	git_repository *repo,
+	git_attr_session *attr_session,
+	git_filter_def *fdef,
+	const git_filter_source *src)
 {
 	int error;
 	size_t i;
 	const char **strs = git__calloc(fdef->nattrs, sizeof(const char *));
 	GITERR_CHECK_ALLOC(strs);
 
-	error = git_attr_get_many(
-		strs, src->repo, 0, src->path, fdef->nattrs, fdef->attrs);
+	error = git_attr_get_many_with_session(
+		strs, repo, attr_session, 0, src->path, fdef->nattrs, fdef->attrs);
 
 	/* if no values were found but no matches are needed, it's okay! */
 	if (error == GIT_ENOTFOUND && !fdef->nmatches) {
@@ -448,9 +452,10 @@ int git_filter_list_new(
 	return filter_list_new(out, &src);
 }
 
-int git_filter_list_load(
+int git_filter_list__load_with_attr_session(
 	git_filter_list **filters,
 	git_repository *repo,
+	git_attr_session *attr_session,
 	git_blob *blob, /* can be NULL */
 	const char *path,
 	git_filter_mode_t mode,
@@ -481,7 +486,9 @@ int git_filter_list_load(
 			continue;
 
 		if (fdef->nattrs > 0) {
-			error = filter_list_check_attributes(&values, fdef, &src);
+			error = filter_list_check_attributes(
+				&values, repo, attr_session, fdef, &src);
+
 			if (error == GIT_ENOTFOUND) {
 				error = 0;
 				continue;
@@ -523,6 +530,18 @@ int git_filter_list_load(
 	return error;
 }
 
+int git_filter_list_load(
+	git_filter_list **filters,
+	git_repository *repo,
+	git_blob *blob, /* can be NULL */
+	const char *path,
+	git_filter_mode_t mode,
+	uint32_t options)
+{
+	return git_filter_list__load_with_attr_session(
+		filters, repo, NULL, blob, path, mode, options);
+}
+
 void git_filter_list_free(git_filter_list *fl)
 {
 	uint32_t i;
diff --git a/src/filter.h b/src/filter.h
index 5a36610..390ffeb 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -8,6 +8,7 @@
 #define INCLUDE_filter_h__
 
 #include "common.h"
+#include "attr_file.h"
 #include "git2/filter.h"
 
 /* Amount of file to examine for NUL byte when checking binary-ness */
@@ -25,6 +26,15 @@ typedef enum {
 
 extern void git_filter_free(git_filter *filter);
 
+extern int git_filter_list__load_with_attr_session(
+	git_filter_list **filters,
+	git_repository *repo,
+	git_attr_session *attr_session,
+	git_blob *blob, /* can be NULL */
+	const char *path,
+	git_filter_mode_t mode,
+	uint32_t options);
+
 /*
  * Available filters
  */
diff --git a/src/ignore.c b/src/ignore.c
index 6e00f7d..dd299f0 100644
--- a/src/ignore.c
+++ b/src/ignore.c
@@ -161,7 +161,7 @@ static int push_ignore_file(
 	git_attr_file *file = NULL;
 
 	error = git_attr_cache__get(
-		&file, ignores->repo, GIT_ATTR_FILE__FROM_FILE,
+		&file, ignores->repo, NULL, GIT_ATTR_FILE__FROM_FILE,
 		base, filename, parse_ignore_file);
 	if (error < 0)
 		return error;
@@ -189,7 +189,7 @@ static int get_internal_ignores(git_attr_file **out, git_repository *repo)
 		return error;
 
 	error = git_attr_cache__get(
-		out, repo, GIT_ATTR_FILE__IN_MEMORY, NULL, GIT_IGNORE_INTERNAL, NULL);
+		out, repo, NULL, GIT_ATTR_FILE__IN_MEMORY, NULL, GIT_IGNORE_INTERNAL, NULL);
 
 	/* if internal rules list is empty, insert default rules */
 	if (!error && !(*out)->rules.length)
diff --git a/src/repository.h b/src/repository.h
index 6da8c28..dffa9a8 100644
--- a/src/repository.h
+++ b/src/repository.h
@@ -133,6 +133,8 @@ struct git_repository {
 		has_8dot3_default:1;
 	unsigned int lru_counter;
 
+	git_atomic attr_session_key;
+
 	git_cvar_value cvar_cache[GIT_CVAR_CACHE_MAX];
 };
 
diff --git a/tests/checkout/tree.c b/tests/checkout/tree.c
index f37e6d3..239ee55 100644
--- a/tests/checkout/tree.c
+++ b/tests/checkout/tree.c
@@ -1130,3 +1130,57 @@ void test_checkout_tree__can_collect_perfdata(void)
 
 	git_object_free(obj);
 }
+
+void update_attr_callback(
+	const char *path,
+	size_t completed_steps,
+	size_t total_steps,
+	void *payload)
+{
+	GIT_UNUSED(completed_steps);
+	GIT_UNUSED(total_steps);
+	GIT_UNUSED(payload);
+
+	if (path && strcmp(path, "ident1.txt") == 0)
+		cl_git_write2file("testrepo/.gitattributes",
+			"*.txt ident\n", 12, O_RDWR|O_CREAT, 0666);
+}
+
+void test_checkout_tree__caches_attributes_during_checkout(void)
+{
+	git_checkout_options opts = GIT_CHECKOUT_OPTIONS_INIT;
+	git_oid oid;
+	git_object *obj = NULL;
+	git_buf ident1 = GIT_BUF_INIT, ident2 = GIT_BUF_INIT;
+	char *ident_paths[] = { "ident1.txt", "ident2.txt" };
+
+	opts.progress_cb = update_attr_callback;
+
+	assert_on_branch(g_repo, "master");
+	opts.checkout_strategy = GIT_CHECKOUT_FORCE;
+	opts.paths.strings = ident_paths;
+	opts.paths.count = 2;
+
+	cl_git_pass(git_reference_name_to_id(&oid, g_repo, "refs/heads/ident"));
+	cl_git_pass(git_object_lookup(&obj, g_repo, &oid, GIT_OBJ_ANY));
+
+	cl_git_pass(git_checkout_tree(g_repo, obj, &opts));
+
+	cl_git_pass(git_futils_readbuffer(&ident1, "testrepo/ident1.txt"));
+	cl_git_pass(git_futils_readbuffer(&ident2, "testrepo/ident2.txt"));
+
+	cl_assert_equal_strn(ident1.ptr, "# $Id$", 6);
+	cl_assert_equal_strn(ident2.ptr, "# $Id$", 6);
+
+	cl_git_pass(git_checkout_tree(g_repo, obj, &opts));
+
+	cl_git_pass(git_futils_readbuffer(&ident1, "testrepo/ident1.txt"));
+	cl_git_pass(git_futils_readbuffer(&ident2, "testrepo/ident2.txt"));
+
+	cl_assert_equal_strn(ident1.ptr, "# $Id: ", 7);
+	cl_assert_equal_strn(ident2.ptr, "# $Id: ", 7);
+
+	git_buf_free(&ident1);
+	git_buf_free(&ident2);
+	git_object_free(obj);
+}
diff --git a/tests/refs/list.c b/tests/refs/list.c
index de5c0fd..374943b 100644
--- a/tests/refs/list.c
+++ b/tests/refs/list.c
@@ -36,7 +36,7 @@ void test_refs_list__all(void)
 	/* We have exactly 12 refs in total if we include the packed ones:
 	 * there is a reference that exists both in the packfile and as
 	 * loose, but we only list it once */
-	cl_assert_equal_i((int)ref_list.count, 14);
+	cl_assert_equal_i((int)ref_list.count, 15);
 
 	git_strarray_free(&ref_list);
 }
@@ -51,7 +51,7 @@ void test_refs_list__do_not_retrieve_references_which_name_end_with_a_lock_exten
 		"144344043ba4d4a405da03de3844aa829ae8be0e\n");
 
 	cl_git_pass(git_reference_list(&ref_list, g_repo));
-	cl_assert_equal_i((int)ref_list.count, 14);
+	cl_assert_equal_i((int)ref_list.count, 15);
 
 	git_strarray_free(&ref_list);
 }
diff --git a/tests/repo/iterator.c b/tests/repo/iterator.c
index a1aa4b2..26e8954 100644
--- a/tests/repo/iterator.c
+++ b/tests/repo/iterator.c
@@ -906,6 +906,7 @@ void test_repo_iterator__fs2(void)
 	static const char *expect_base[] = {
 		"heads/br2",
 		"heads/dir",
+		"heads/ident",
 		"heads/long-file-name",
 		"heads/master",
 		"heads/packed-test",
@@ -923,7 +924,7 @@ void test_repo_iterator__fs2(void)
 
 	cl_git_pass(git_iterator_for_filesystem(
 		&i, "testrepo/.git/refs", 0, NULL, NULL));
-	expect_iterator_items(i, 12, expect_base, 12, expect_base);
+	expect_iterator_items(i, 13, expect_base, 13, expect_base);
 	git_iterator_free(i);
 }
 
diff --git a/tests/resources/testrepo/.gitted/objects/6f/d5c7dd2ab27b48c493023f794be09861e9045f b/tests/resources/testrepo/.gitted/objects/6f/d5c7dd2ab27b48c493023f794be09861e9045f
new file mode 100644
index 0000000..7f0c6fe
--- /dev/null
+++ b/tests/resources/testrepo/.gitted/objects/6f/d5c7dd2ab27b48c493023f794be09861e9045f
@@ -0,0 +1 @@
+x
��A�!D��}�G�
�Mr�\�m[F��1��1gȢ�(�G�Rr3�Co"�v�^hq�<7��A�Y{��"�&$�D�S�g��([B!�ΡwƳY��g���l$%E�������ֲ�'\d�_w-�[�k�'����1h���Z�t��B��&;��:��A���"�m�%�
�V
\ No newline at end of file
diff --git a/tests/resources/testrepo/.gitted/objects/c3/6d8ea75da8cb510fcb0c408c1d7e53f9a99dbe b/tests/resources/testrepo/.gitted/objects/c3/6d8ea75da8cb510fcb0c408c1d7e53f9a99dbe
new file mode 100644
index 0000000..0975f7f
Binary files /dev/null and b/tests/resources/testrepo/.gitted/objects/c3/6d8ea75da8cb510fcb0c408c1d7e53f9a99dbe differ
diff --git a/tests/resources/testrepo/.gitted/objects/e3/6900c3224db4adf4c7f7a09d4ac80247978a13 b/tests/resources/testrepo/.gitted/objects/e3/6900c3224db4adf4c7f7a09d4ac80247978a13
new file mode 100644
index 0000000..e74291f
Binary files /dev/null and b/tests/resources/testrepo/.gitted/objects/e3/6900c3224db4adf4c7f7a09d4ac80247978a13 differ
diff --git a/tests/resources/testrepo/.gitted/refs/heads/ident b/tests/resources/testrepo/.gitted/refs/heads/ident
new file mode 100644
index 0000000..2cfd880
--- /dev/null
+++ b/tests/resources/testrepo/.gitted/refs/heads/ident
@@ -0,0 +1 @@
+6fd5c7dd2ab27b48c493023f794be09861e9045f
diff --git a/tests/revwalk/basic.c b/tests/revwalk/basic.c
index ff05fa2..4ae9527 100644
--- a/tests/revwalk/basic.c
+++ b/tests/revwalk/basic.c
@@ -177,7 +177,7 @@ void test_revwalk_basic__glob_heads_with_invalid(void)
 		/* walking */;
 
 	/* git log --branches --oneline | wc -l => 16 */
-	cl_assert_equal_i(17, i);
+	cl_assert_equal_i(18, i);
 }
 
 void test_revwalk_basic__push_head(void)