thodg/libgit2

diff --git a/cmake/Modules/FindStatNsec.cmake b/cmake/Modules/FindStatNsec.cmake
index fa550a2..a4a09fa 100644
--- a/cmake/Modules/FindStatNsec.cmake
+++ b/cmake/Modules/FindStatNsec.cmake
@@ -1,3 +1,5 @@
+INCLUDE(FeatureSummary)
+
 CHECK_STRUCT_HAS_MEMBER ("struct stat" st_mtim "sys/types.h;sys/stat.h"
 	HAVE_STRUCT_STAT_ST_MTIM LANGUAGE C)
 CHECK_STRUCT_HAS_MEMBER ("struct stat" st_mtimespec "sys/types.h;sys/stat.h"
@@ -17,4 +19,8 @@ ENDIF()
 
 IF (HAVE_STRUCT_STAT_NSEC OR WIN32)
 	OPTION( USE_NSEC		"Care about sub-second file mtimes and ctimes"	ON  )
+ELSE()
+	SET(USE_NSEC OFF)
 ENDIF()
+
+ADD_FEATURE_INFO(nanoseconds USE_NSEC "whether to use sub-second file mtimes and ctimes")
diff --git a/examples/common.h b/examples/common.h
index c1d444e..724a5c0 100644
--- a/examples/common.h
+++ b/examples/common.h
@@ -39,6 +39,7 @@ extern int lg2_blame(git_repository *repo, int argc, char **argv);
 extern int lg2_cat_file(git_repository *repo, int argc, char **argv);
 extern int lg2_checkout(git_repository *repo, int argc, char **argv);
 extern int lg2_clone(git_repository *repo, int argc, char **argv);
+extern int lg2_config(git_repository *repo, int argc, char **argv);
 extern int lg2_describe(git_repository *repo, int argc, char **argv);
 extern int lg2_diff(git_repository *repo, int argc, char **argv);
 extern int lg2_fetch(git_repository *repo, int argc, char **argv);
diff --git a/examples/config.c b/examples/config.c
new file mode 100644
index 0000000..f7fa70e
--- /dev/null
+++ b/examples/config.c
@@ -0,0 +1,62 @@
+/*
+ * libgit2 "config" example - shows how to use the config API
+ *
+ * Written by the libgit2 contributors
+ *
+ * To the extent possible under law, the author(s) have dedicated all copyright
+ * and related and neighboring rights to this software to the public domain
+ * worldwide. This software is distributed without any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication along
+ * with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#include "common.h"
+
+static int config_get(git_config *cfg, const char *key)
+{
+	git_config_entry *entry;
+	int error;
+
+	if ((error = git_config_get_entry(&entry, cfg, key)) < 0) {
+		if (error != GIT_ENOTFOUND)
+			printf("Unable to get configuration: %s\n", git_error_last()->message);
+		return 1;
+	}
+
+	puts(entry->value);
+	return 0;
+}
+
+static int config_set(git_config *cfg, const char *key, const char *value)
+{
+	if (git_config_set_string(cfg, key, value) < 0) {
+		printf("Unable to set configuration: %s\n", git_error_last()->message);
+		return 1;
+	}
+	return 0;
+}
+
+int lg2_config(git_repository *repo, int argc, char **argv)
+{
+	git_config *cfg;
+	int error;
+
+	if ((error = git_repository_config(&cfg, repo)) < 0) {
+		printf("Unable to obtain repository config: %s\n", git_error_last()->message);
+		goto out;
+	}
+
+	if (argc == 2) {
+		error = config_get(cfg, argv[1]);
+	} else if (argc == 3) {
+		error = config_set(cfg, argv[1], argv[2]);
+	} else {
+		printf("USAGE: %s config <KEY> [<VALUE>]\n", argv[0]);
+		error = 1;
+	}
+
+out:
+	return error;
+}
diff --git a/examples/lg2.c b/examples/lg2.c
index b3df02d..4ee0110 100644
--- a/examples/lg2.c
+++ b/examples/lg2.c
@@ -15,6 +15,7 @@ struct {
 	{ "cat-file",     lg2_cat_file,     1 },
 	{ "checkout",     lg2_checkout,     1 },
 	{ "clone",        lg2_clone,        0 },
+	{ "config",       lg2_config,       1 },
 	{ "describe",     lg2_describe,     1 },
 	{ "diff",         lg2_diff,         1 },
 	{ "fetch",        lg2_fetch,        1 },
diff --git a/src/config_file.c b/src/config_file.c
index 27b9cc5..3865327 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -44,7 +44,7 @@ typedef struct {
 	git_filebuf locked_buf;
 	git_buf locked_content;
 
-	struct config_file file;
+	git_config_file file;
 } diskfile_backend;
 
 typedef struct {
@@ -62,6 +62,7 @@ typedef struct {
 } diskfile_parse_state;
 
 static int config_read(git_config_entries *entries, const git_repository *repo, git_config_file *file, git_config_level_t level, int depth);
+static int config_read_buffer(git_config_entries *entries, const git_repository *repo, git_config_file *file, git_config_level_t level, int depth, const char *buf, size_t buflen);
 static int config_write(diskfile_backend *cfg, const char *orig_key, const char *key, const p_regex_t *preg, const char *value);
 static char *escape_value(const char *ptr);
 
@@ -95,9 +96,9 @@ static git_config_entries *diskfile_entries_take(diskfile_header *h)
 	return entries;
 }
 
-static void config_file_clear(struct config_file *file)
+static void config_file_clear(git_config_file *file)
 {
-	struct config_file *include;
+	git_config_file *include;
 	uint32_t i;
 
 	if (file == NULL)
@@ -133,7 +134,7 @@ static int config_open(git_config_backend *cfg, git_config_level_t level, const 
 	return res;
 }
 
-static int config_is_modified(int *modified, struct config_file *file)
+static int config_is_modified(int *modified, git_config_file *file)
 {
 	git_config_file *include;
 	git_buf buf = GIT_BUF_INIT;
@@ -143,6 +144,9 @@ static int config_is_modified(int *modified, struct config_file *file)
 
 	*modified = 0;
 
+	if (!git_futils_filestamp_check(&file->stamp, file->path))
+		goto check_includes;
+
 	if ((error = git_futils_readbuffer(&buf, file->path)) < 0)
 		goto out;
 
@@ -154,6 +158,7 @@ static int config_is_modified(int *modified, struct config_file *file)
 		goto out;
 	}
 
+check_includes:
 	git_array_foreach(file->includes, i, include) {
 		if ((error = config_is_modified(modified, include)) < 0 || *modified)
 			goto out;
@@ -165,48 +170,74 @@ out:
 	return error;
 }
 
-static int config_refresh(git_config_backend *cfg)
+static int config_set_entries(git_config_backend *cfg, git_config_entries *entries)
 {
 	diskfile_backend *b = (diskfile_backend *)cfg;
-	git_config_entries *entries = NULL, *tmp;
+	git_config_entries *old = NULL;
 	git_config_file *include;
-	int error, modified;
-	uint32_t i;
+	int error;
+	size_t i;
 
 	if (b->header.parent.readonly)
 		return config_error_readonly();
 
-	error = config_is_modified(&modified, &b->file);
-	if (error < 0 && error != GIT_ENOTFOUND)
-		goto out;
-
-	if (!modified)
-		return 0;
-
-	if ((error = git_config_entries_new(&entries)) < 0)
-		goto out;
-
-	/* Reparse the current configuration */
-	git_array_foreach(b->file.includes, i, include) {
+	git_array_foreach(b->file.includes, i, include)
 		config_file_clear(include);
-	}
 	git_array_clear(b->file.includes);
 
-	if ((error = config_read(entries, b->header.repo, &b->file, b->header.level, 0)) < 0)
-		goto out;
-
 	if ((error = git_mutex_lock(&b->header.values_mutex)) < 0) {
 		git_error_set(GIT_ERROR_OS, "failed to lock config backend");
 		goto out;
 	}
 
-	tmp = b->header.entries;
+	old = b->header.entries;
 	b->header.entries = entries;
-	entries = tmp;
 
 	git_mutex_unlock(&b->header.values_mutex);
 
 out:
+	git_config_entries_free(old);
+	return error;
+}
+
+static int config_refresh_from_buffer(git_config_backend *cfg, const char *buf, size_t buflen)
+{
+	diskfile_backend *b = GIT_CONTAINER_OF(cfg, diskfile_backend, header.parent);
+	git_config_entries *entries = NULL;
+	int error;
+
+	if ((error = git_config_entries_new(&entries)) < 0 ||
+	    (error = config_read_buffer(entries, b->header.repo, &b->file,
+					b->header.level, 0, buf, buflen)) < 0 ||
+	    (error = config_set_entries(cfg, entries)) < 0)
+		goto out;
+
+	entries = NULL;
+out:
+	git_config_entries_free(entries);
+	return error;
+}
+
+static int config_refresh(git_config_backend *cfg)
+{
+	diskfile_backend *b = GIT_CONTAINER_OF(cfg, diskfile_backend, header.parent);
+	git_config_entries *entries = NULL;
+	int error, modified;
+
+	error = config_is_modified(&modified, &b->file);
+	if (error < 0 && error != GIT_ENOTFOUND)
+		goto out;
+
+	if (!modified)
+		return 0;
+
+	if ((error = git_config_entries_new(&entries)) < 0 ||
+	    (error = config_read(entries, b->header.repo, &b->file, b->header.level, 0)) < 0 ||
+	    (error = config_set_entries(cfg, entries)) < 0)
+		goto out;
+
+	entries = NULL;
+out:
 	git_config_entries_free(entries);
 
 	return (error == GIT_ENOTFOUND) ? 0 : error;
@@ -280,8 +311,6 @@ static int config_set(git_config_backend *cfg, const char *name, const char *val
 	if ((error = config_write(b, name, key, NULL, esc_value)) < 0)
 		goto out;
 
-	error = config_refresh(cfg);
-
 out:
 	git_config_entries_free(entries);
 	git__free(esc_value);
@@ -348,8 +377,6 @@ static int config_set_multivar(
 	if ((result = config_write(b, name, key, &preg, value)) < 0)
 		goto out;
 
-	result = config_refresh(cfg);
-
 out:
 	git__free(key);
 	p_regfree(&preg);
@@ -381,9 +408,6 @@ static int config_delete(git_config_backend *cfg, const char *name)
 	if ((error = config_write(b, name, entry->name, NULL, NULL)) < 0)
 		goto out;
 
-	if ((error =  config_refresh(cfg)) < 0)
-		goto out;
-
 out:
 	git_config_entries_free(entries);
 	git__free(key);
@@ -422,9 +446,6 @@ static int config_delete_multivar(git_config_backend *cfg, const char *name, con
 	if ((result = config_write(b, name, key, &preg, NULL)) < 0)
 		goto out;
 
-	if ((result = config_refresh(cfg)) < 0)
-		goto out;
-
 out:
 	git_config_entries_free(entries);
 	git__free(key);
@@ -659,7 +680,7 @@ static char *escape_value(const char *ptr)
 static int parse_include(git_config_parser *reader,
 	diskfile_parse_state *parse_data, const char *file)
 {
-	struct config_file *include;
+	git_config_file *include;
 	git_buf path = GIT_BUF_INIT;
 	char *dir;
 	int result;
@@ -851,16 +872,17 @@ static int read_on_variable(
 	return result;
 }
 
-static int config_read(
+static int config_read_buffer(
 	git_config_entries *entries,
 	const git_repository *repo,
 	git_config_file *file,
 	git_config_level_t level,
-	int depth)
+	int depth,
+	const char *buf,
+	size_t buflen)
 {
 	diskfile_parse_state parse_data;
 	git_config_parser reader;
-	git_buf contents = GIT_BUF_INIT;
 	int error;
 
 	if (depth >= MAX_INCLUDE_DEPTH) {
@@ -868,21 +890,15 @@ static int config_read(
 		return -1;
 	}
 
-	if ((error = git_futils_readbuffer(&contents, file->path)) < 0)
-		goto out;
-
-	git_parse_ctx_init(&reader.ctx, contents.ptr, contents.size);
-
-	if ((error = git_hash_buf(&file->checksum, contents.ptr, contents.size)) < 0)
-		goto out;
-
 	/* Initialize the reading position */
 	reader.file = file;
-	git_parse_ctx_init(&reader.ctx, contents.ptr, contents.size);
+	git_parse_ctx_init(&reader.ctx, buf, buflen);
 
 	/* If the file is empty, there's nothing for us to do */
-	if (!reader.ctx.content || *reader.ctx.content == '\0')
+	if (!reader.ctx.content || *reader.ctx.content == '\0') {
+		error = 0;
 		goto out;
+	}
 
 	parse_data.repo = repo;
 	parse_data.file_path = file->path;
@@ -893,6 +909,37 @@ static int config_read(
 	error = git_config_parse(&reader, NULL, read_on_variable, NULL, NULL, &parse_data);
 
 out:
+	return error;
+}
+
+static int config_read(
+	git_config_entries *entries,
+	const git_repository *repo,
+	git_config_file *file,
+	git_config_level_t level,
+	int depth)
+{
+	git_buf contents = GIT_BUF_INIT;
+	struct stat st;
+	int error;
+
+	if (p_stat(file->path, &st) < 0) {
+		error = git_path_set_error(errno, file->path, "stat");
+		goto out;
+	}
+
+	if ((error = git_futils_readbuffer(&contents, file->path)) < 0)
+		goto out;
+
+	git_futils_filestamp_set_from_stat(&file->stamp, &st);
+	if ((error = git_hash_buf(&file->checksum, contents.ptr, contents.size)) < 0)
+		goto out;
+
+	if ((error = config_read_buffer(entries, repo, file, level, depth,
+					contents.ptr, contents.size)) < 0)
+		goto out;
+
+out:
 	git_buf_dispose(&contents);
 	return error;
 }
@@ -1197,7 +1244,12 @@ static int config_write(diskfile_backend *cfg, const char *orig_key, const char 
 		git_buf_attach(&cfg->locked_content, git_buf_detach(&buf), len);
 	} else {
 		git_filebuf_write(&file, git_buf_cstr(&buf), git_buf_len(&buf));
-		result = git_filebuf_commit(&file);
+
+		if ((result = git_filebuf_commit(&file)) < 0)
+			goto done;
+
+		if ((result = config_refresh_from_buffer(&cfg->header.parent, buf.ptr, buf.size)) < 0)
+			goto done;
 	}
 
 done:
diff --git a/src/config_parse.h b/src/config_parse.h
index 81a13fc..4db31bd 100644
--- a/src/config_parse.h
+++ b/src/config_parse.h
@@ -8,7 +8,9 @@
 #define INCLUDE_config_parse_h__
 
 #include "common.h"
+
 #include "array.h"
+#include "fileops.h"
 #include "oid.h"
 #include "parse.h"
 
@@ -16,13 +18,14 @@ extern const char *git_config_escapes;
 extern const char *git_config_escaped;
 
 typedef struct config_file {
+	git_futils_filestamp stamp;
 	git_oid checksum;
 	char *path;
 	git_array_t(struct config_file) includes;
 } git_config_file;
 
 typedef struct {
-	struct config_file *file;
+	git_config_file *file;
 	git_parse_ctx ctx;
 } git_config_parser;
 
diff --git a/tests/clar_libgit2.h b/tests/clar_libgit2.h
index 5ea62e7..63cd266 100644
--- a/tests/clar_libgit2.h
+++ b/tests/clar_libgit2.h
@@ -220,6 +220,12 @@ void cl_fake_home_cleanup(void *);
 void cl_sandbox_set_search_path_defaults(void);
 
 #ifdef GIT_WIN32
+# define cl_msleep(x) Sleep(x)
+#else
+# define cl_msleep(x) usleep(1000 * (x))
+#endif
+
+#ifdef GIT_WIN32
 bool cl_sandbox_supports_8dot3(void);
 #endif
 
diff --git a/tests/config/stress.c b/tests/config/stress.c
index d86a11d..ad09c87 100644
--- a/tests/config/stress.c
+++ b/tests/config/stress.c
@@ -123,6 +123,7 @@ void test_config_stress__quick_write(void)
 	for (i = 0; i < 10; i++) {
 		int32_t val;
 		cl_git_pass(git_config_set_int32(config_w, key, i));
+		cl_msleep(1);
 		cl_git_pass(git_config_get_int32(&val, config_r, key));
 		cl_assert_equal_i(i, val);
 	}