remote: Prevent create() from blindly overwriting

include/git2/remote.h

@@ -41,7 +41,7 @@ typedef int (*git_remote_rename_problem_cb)(const char *problematic_refspec, voi
  * @param repo the repository in which to create the remote
  * @param name the remote's name
  * @param url the remote's url
- * @return 0, GIT_EINVALIDSPEC or an error code
+ * @return 0, GIT_EINVALIDSPEC, GIT_EEXISTS or an error code
  */
 GIT_EXTERN(int) git_remote_create(
 		git_remote **out,

src/remote.c

@@ -106,11 +106,6 @@ static int create_internal(git_remote **out, git_repository *repo, const char *n
 	GITERR_CHECK_ALLOC(remote->url);
 
 	if (name != NULL) {
-		if ((error = ensure_remote_name_is_valid(name)) < 0) {
-			error = GIT_EINVALIDSPEC;
-			goto on_error;
-		}
-
 		remote->name = git__strdup(name);
 		GITERR_CHECK_ALLOC(remote->name);
 	}
@@ -135,6 +130,8 @@ on_error:
 	return error;
 }
 
+extern int ensure_remote_doesnot_exist(git_repository *repo, const char *name);
+
 int git_remote_create(git_remote **out, git_repository *repo, const char *name, const char *url)
 {
 	git_buf buf = GIT_BUF_INIT;
@@ -143,6 +140,9 @@ int git_remote_create(git_remote **out, git_repository *repo, const char *name,
 	if ((error = ensure_remote_name_is_valid(name)) < 0)
 		return error;
 
+	if ((error = ensure_remote_doesnot_exist(repo, name)) < 0)
+		return error;
+
 	if (git_buf_printf(&buf, "+refs/heads/*:refs/remotes/%s/*", name) < 0)
 		return -1;
 

tests-clar/network/remotes.c

@@ -346,3 +346,14 @@ void test_network_remotes__check_structure_version(void)
 	err = giterr_last();
 	cl_assert_equal_i(GITERR_INVALID, err->klass);
 }
+
+void test_network_remotes__cannot_create_a_remote_which_name_conflicts_with_an_existing_remote(void)
+{
+	git_remote *remote = NULL;
+
+	cl_assert_equal_i(
+		GIT_EEXISTS,
+		git_remote_create(&remote, _repo, "test", "git://github.com/libgit2/libgit2"));
+
+	cl_assert_equal_p(remote, NULL);
+}