Adding git_config_foreach_match() iteration fn

Adding a new config iteration function that let's you iterate
over just the config entries that match a particular regular
expression.  The old foreach becomes a simple use of this with
an empty pattern.

This also fixes an apparent bug in the existing `git_config_foreach`
where returning a non-zero value from the iteration callback was
not correctly aborting the iteration and the returned value was
not being propogated back to the caller of foreach.

Added to tests to cover all these changes.

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

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;

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;
 	}
 

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

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")