Add `git_tag_list`

Lists all the tag references in a repository using a custom callback.
Includes unit tests courtesy of Emeric Fermas <3

include/git2/tag.h

@@ -275,6 +275,23 @@ GIT_EXTERN(int) git_tag_delete(
 		git_repository *repo,
 		const char *tag_name);
 
+/**
+ * Fill a list with all the tags in the Repository
+ *
+ * The string array will be filled with the names of the
+ * matching tags; these values are owned by the user and
+ * should be free'd manually when no longer needed, using
+ * `git_strarray_free`.
+ *
+ * @param array Pointer to a git_strarray structure where
+ *		the tag names will be stored
+ * @param repo Repository where to find the tags
+ * @return 0 on success; error code otherwise
+ */
+GIT_EXTERN(int) git_tag_list(
+		git_strarray *tag_names,
+		git_repository *repo);
+
 /** @} */
 GIT_END_DECL
 #endif

src/tag.c

@@ -377,3 +377,29 @@ int git_tag__parse(git_tag *tag, git_odb_object *obj)
 	return parse_tag_buffer(tag, obj->raw.data, (char *)obj->raw.data + obj->raw.len);
 }
 
+static int tag_list_cb(const char *tag_name, void *payload)
+{
+	if (git__prefixcmp(tag_name, GIT_REFS_TAGS_DIR) == 0)
+		return git_vector_insert((git_vector *)payload, git__strdup(tag_name));
+
+	return GIT_SUCCESS;
+}
+
+int git_tag_list(git_strarray *tag_names, git_repository *repo)
+{
+	int error;
+	git_vector taglist;
+
+	if (git_vector_init(&taglist, 8, NULL) < GIT_SUCCESS)
+		return GIT_ENOMEM;
+
+	error = git_reference_listcb(repo, GIT_REF_OID|GIT_REF_PACKED, &tag_list_cb, (void *)&taglist);
+	if (error < GIT_SUCCESS) {
+		git_vector_free(&taglist);
+		return error;
+	}
+
+	tag_names->strings = (char **)taglist.contents;
+	tag_names->count = taglist.length;
+	return GIT_SUCCESS;
+}

tests/t08-tag.c

@@ -64,6 +64,19 @@ BEGIN_TEST(read0, "read and parse a tag from the repository")
 	git_repository_free(repo);
 END_TEST
 
+BEGIN_TEST(read1, "list all tag names from the repository")
+	git_repository *repo;
+	git_strarray tag_list;
+
+	must_pass(git_repository_open(&repo, REPOSITORY_FOLDER));
+	must_pass(git_tag_list(&tag_list, repo));
+
+	must_be_true(tag_list.count == 3);
+
+	git_strarray_free(&tag_list);
+	git_repository_free(repo);
+END_TEST
+
 
 #define TAGGER_NAME "Vicent Marti"
 #define TAGGER_EMAIL "vicent@github.com"
@@ -227,6 +240,7 @@ END_TEST
 
 BEGIN_SUITE(tag)
 	ADD_TEST(read0);
+	ADD_TEST(read1);
 	ADD_TEST(write0);
 	ADD_TEST(write1);
 	ADD_TEST(write2);