ref-filter API user: add and use a ref_sorting_release()

Add a ref_sorting_release() and use it for some of the current API
users, the ref_sorting_default() function and its siblings will do a
malloc() which wasn't being free'd previously.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/for-each-ref.c

@@ -96,6 +96,6 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	ref_array_clear(&array);
 	free_commit_list(filter.with_commit);
 	free_commit_list(filter.no_commit);
-	UNLEAK(sorting);
+	ref_sorting_release(sorting);
 	return 0;
 }

builtin/tag.c

@@ -630,6 +630,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		       find_unique_abbrev(&prev, DEFAULT_ABBREV));
 
 cleanup:
+	ref_sorting_release(sorting);
 	strbuf_release(&buf);
 	strbuf_release(&ref);
 	strbuf_release(&reflog_msg);

ref-filter.c

@@ -2705,6 +2705,15 @@ int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
+void ref_sorting_release(struct ref_sorting *sorting)
+{
+	while (sorting) {
+		struct ref_sorting *next = sorting->next;
+		free(sorting);
+		sorting = next;
+	}
+}
+
 int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset)
 {
 	struct ref_filter *rf = opt->value;

ref-filter.h

@@ -127,6 +127,8 @@ void parse_ref_sorting(struct ref_sorting **sorting_tail, const char *atom);
 int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset);
 /*  Default sort option based on refname */
 struct ref_sorting *ref_default_sorting(void);
+/* Release a "struct ref_sorting" */
+void ref_sorting_release(struct ref_sorting *);
 /*  Function to parse --merged and --no-merged options */
 int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset);
 /*  Get the current HEAD's description */