thodg/libgit2

diff --git a/include/git2/config.h b/include/git2/config.h
index 36946c4..c46e7fc 100644
--- a/include/git2/config.h
+++ b/include/git2/config.h
@@ -33,7 +33,7 @@ struct git_config_file {
 	int (*set)(struct git_config_file *, const char *key, const char *value);
 	int (*set_multivar)(git_config_file *cfg, const char *name, const char *regexp, const char *value);
 	int (*del)(struct git_config_file *, const char *key);
-	int (*foreach)(struct git_config_file *, int (*fn)(const char *, const char *, void *), void *data);
+	int (*foreach)(struct git_config_file *, const char *, int (*fn)(const char *, const char *, void *), void *data);
 	void (*free)(struct git_config_file *);
 };
 
@@ -314,6 +314,24 @@ GIT_EXTERN(int) git_config_foreach(
 	int (*callback)(const char *var_name, const char *value, void *payload),
 	void *payload);
 
+/**
+ * Perform an operation on each config variable matching a regular expression.
+ *
+ * This behaviors like `git_config_foreach` with an additional filter of a
+ * regular expression that filters which config keys are passed to the
+ * callback.
+ *
+ * @param cfg where to get the variables from
+ * @param regexp regular expression to match against config names
+ * @param callback the function to call on each variable
+ * @param payload the data to pass to the callback
+ * @return 0 or the return value of the callback which didn't return 0
+ */
+GIT_EXTERN(int) git_config_foreach_match(
+	git_config *cfg,
+	const char *regexp,
+	int (*callback)(const char *var_name, const char *value, void *payload),
+	void *payload);
 
 /**
  * Query the value of a config variable and return it mapped to
diff --git a/src/config.c b/src/config.c
index d18b85c..98fb3b2 100644
--- a/src/config.c
+++ b/src/config.c
@@ -136,17 +136,27 @@ int git_config_add_file(git_config *cfg, git_config_file *file, int priority)
  * Loop over all the variables
  */
 
-int git_config_foreach(git_config *cfg, int (*fn)(const char *, const char *, void *), void *data)
+int git_config_foreach(
+	git_config *cfg, int (*fn)(const char *, const char *, void *), void *data)
+{
+	return git_config_foreach_match(cfg, NULL, fn, data);
+}
+
+int git_config_foreach_match(
+	git_config *cfg,
+	const char *regexp,
+	int (*fn)(const char *, const char *, void *),
+	void *data)
 {
 	int ret = 0;
 	unsigned int i;
 	file_internal *internal;
 	git_config_file *file;
 
-	for(i = 0; i < cfg->files.length && ret == 0; ++i) {
+	for (i = 0; i < cfg->files.length && ret == 0; ++i) {
 		internal = git_vector_get(&cfg->files, i);
 		file = internal->file;
-		ret = file->foreach(file, fn, data);
+		ret = file->foreach(file, regexp, fn, data);
 	}
 
 	return ret;
diff --git a/src/config_file.c b/src/config_file.c
index fd1aa8d..1f3ebfc 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -188,25 +188,46 @@ static void backend_free(git_config_file *_backend)
 	git__free(backend);
 }
 
-static int file_foreach(git_config_file *backend, int (*fn)(const char *, const char *, void *), void *data)
+static int file_foreach(
+	git_config_file *backend,
+	const char *regexp,
+	int (*fn)(const char *, const char *, void *),
+	void *data)
 {
 	diskfile_backend *b = (diskfile_backend *)backend;
 	cvar_t *var;
 	const char *key;
+	regex_t regex;
+	int result = 0;
 
 	if (!b->values)
 		return 0;
 
+	if (regexp != NULL) {
+		if ((result = regcomp(&regex, regexp, REG_EXTENDED)) < 0) {
+			giterr_set_regex(&regex, result);
+			regfree(&regex);
+			return -1;
+		}
+	}
+
 	git_strmap_foreach(b->values, key, var,
-		do {
-			if (fn(key, var->value, data) < 0)
-				break;
+		for (; var != NULL; var = CVAR_LIST_NEXT(var)) {
+			/* skip non-matching keys if regexp was provided */
+			if (regexp && regexec(&regex, key, 0, NULL, 0) != 0)
+				continue;
 
-			var = CVAR_LIST_NEXT(var);
-		} while (var != NULL);
+			/* abort iterator on non-zero return value */
+			if ((result = fn(key, var->value, data)) != 0)
+				goto cleanup;
+		}
 	);
 
-	return 0;
+cleanup:
+	if (regexp != NULL)
+		regfree(&regex);
+
+	return result;
 }
 
 static int config_set(git_config_file *cfg, const char *name, const char *value)
@@ -337,6 +358,7 @@ static int config_get_multivar(
 		result = regcomp(&regex, regex_str, REG_EXTENDED);
 		if (result < 0) {
 			giterr_set_regex(&regex, result);
+			regfree(&regex);
 			return -1;
 		}
 
@@ -396,6 +418,7 @@ static int config_set_multivar(
 	if (result < 0) {
 		git__free(key);
 		giterr_set_regex(&preg, result);
+		regfree(&preg);
 		return -1;
 	}
 
diff --git a/src/config_file.h b/src/config_file.h
index 0080b57..c312928 100644
--- a/src/config_file.h
+++ b/src/config_file.h
@@ -19,12 +19,27 @@ GIT_INLINE(void) git_config_file_free(git_config_file *cfg)
 	cfg->free(cfg);
 }
 
+GIT_INLINE(int) git_config_file_set_string(
+	git_config_file *cfg, const char *name, const char *value)
+{
+	return cfg->set(cfg, name, value);
+}
+
 GIT_INLINE(int) git_config_file_foreach(
 	git_config_file *cfg,
 	int (*fn)(const char *key, const char *value, void *data),
 	void *data)
 {
-	return cfg->foreach(cfg, fn, data);
+	return cfg->foreach(cfg, NULL, fn, data);
+}
+
+GIT_INLINE(int) git_config_file_foreach_match(
+	git_config_file *cfg,
+	const char *regexp,
+	int (*fn)(const char *key, const char *value, void *data),
+	void *data)
+{
+	return cfg->foreach(cfg, regexp, fn, data);
 }
 
 #endif
diff --git a/tests-clar/config/read.c b/tests-clar/config/read.c
index f33bdd8..a8504da 100644
--- a/tests-clar/config/read.c
+++ b/tests-clar/config/read.c
@@ -191,6 +191,81 @@ void test_config_read__escaping_quotes(void)
 	git_config_free(cfg);
 }
 
+static int count_cfg_entries(
+	const char *var_name, const char *value, void *payload)
+{
+	int *count = payload;
+	GIT_UNUSED(var_name);
+	GIT_UNUSED(value);
+	(*count)++;
+	return 0;
+}
+
+static int cfg_callback_countdown(
+	const char *var_name, const char *value, void *payload)
+{
+	int *count = payload;
+	GIT_UNUSED(var_name);
+	GIT_UNUSED(value);
+	(*count)--;
+	if (*count == 0)
+		return -100;
+	return 0;
+}
+
+void test_config_read__foreach(void)
+{
+	git_config *cfg;
+	int count, ret;
+
+	cl_git_pass(git_config_open_ondisk(&cfg, cl_fixture("config/config9")));
+
+	count = 0;
+	cl_git_pass(git_config_foreach(cfg, count_cfg_entries, &count));
+	cl_assert_equal_i(5, count);
+
+	count = 3;
+	cl_git_fail(ret = git_config_foreach(cfg, cfg_callback_countdown, &count));
+	cl_assert_equal_i(-100, ret);
+
+	git_config_free(cfg);
+}
+
+void test_config_read__foreach_match(void)
+{
+	git_config *cfg;
+	int count;
+
+	cl_git_pass(git_config_open_ondisk(&cfg, cl_fixture("config/config9")));
+
+	count = 0;
+	cl_git_pass(
+		git_config_foreach_match(cfg, "core.*", count_cfg_entries, &count));
+	cl_assert_equal_i(3, count);
+
+	count = 0;
+	cl_git_pass(
+		git_config_foreach_match(cfg, "remote\\.ab.*", count_cfg_entries, &count));
+	cl_assert_equal_i(2, count);
+
+	count = 0;
+	cl_git_pass(
+		git_config_foreach_match(cfg, ".*url$", count_cfg_entries, &count));
+	cl_assert_equal_i(2, count);
+
+	count = 0;
+	cl_git_pass(
+		git_config_foreach_match(cfg, ".*dummy.*", count_cfg_entries, &count));
+	cl_assert_equal_i(2, count);
+
+	count = 0;
+	cl_git_pass(
+		git_config_foreach_match(cfg, ".*nomatch.*", count_cfg_entries, &count));
+	cl_assert_equal_i(0, count);
+
+	git_config_free(cfg);
+}
+
 #if 0
 
 BEGIN_TEST(config10, "a repo's config overrides the global config")