reflog: error when a directory is at reflog path

When a non-empty directory exists and prevents the creation of a
reflog, provide a more informative error message.

src/refdb_fs.c

@@ -1788,10 +1788,17 @@ static int reflog_append(refdb_fs_backend *backend, const git_reference *ref, co
 	/* If the new branch matches part of the namespace of a previously deleted branch,
 	 * there maybe an obsolete/unused directory (or directory hierarchy) in the way.
 	 */
-	if (git_path_isdir(git_buf_cstr(&path)) &&
-		(git_futils_rmdir_r(git_buf_cstr(&path), NULL, GIT_RMDIR_SKIP_NONEMPTY) < 0)) {
-		error = -1;
-		goto cleanup;
+	if (git_path_isdir(git_buf_cstr(&path))) {
+		if ((git_futils_rmdir_r(git_buf_cstr(&path), NULL, GIT_RMDIR_SKIP_NONEMPTY) < 0))
+			error = -1;
+		else if (git_path_isdir(git_buf_cstr(&path))) {
+			giterr_set(GITERR_REFERENCE, "cannot create reflog at '%s', there are reflogs beneath that folder",
+				ref->name);
+			error = GIT_EDIRECTORY;
+		}
+
+		if (error != 0)
+			goto cleanup;
 	}
 
 	error = git_futils_writebuffer(&buf, git_buf_cstr(&path), O_WRONLY|O_CREAT|O_APPEND, GIT_REFLOG_FILE_MODE);

tests/refs/reflog/reflog.c

@@ -143,6 +143,59 @@ void test_refs_reflog_reflog__deleting_the_reference_deletes_the_reflog(void)
 	git_buf_free(&master_log_path);
 }
 
+void test_refs_reflog_reflog__removes_empty_reflog_dir(void)
+{
+	git_reference *ref;
+	git_buf log_path = GIT_BUF_INIT;
+	git_oid id;
+
+	/* Create a new branch pointing at the HEAD */
+	git_oid_fromstr(&id, current_master_tip);
+	cl_git_pass(git_reference_create(&ref, g_repo, "refs/heads/new-dir/new-head", &id, 0, NULL));
+
+	git_buf_joinpath(&log_path, git_repository_path(g_repo), GIT_REFLOG_DIR);
+	git_buf_joinpath(&log_path, git_buf_cstr(&log_path), "refs/heads/new-dir/new-head");
+
+	cl_assert_equal_i(true, git_path_isfile(git_buf_cstr(&log_path)));
+
+	cl_git_pass(git_reference_delete(ref));
+	git_reference_free(ref);
+
+	/* new ref creation should succeed since new-dir is empty */
+	git_oid_fromstr(&id, current_master_tip);
+	cl_git_pass(git_reference_create(&ref, g_repo, "refs/heads/new-dir", &id, 0, NULL));
+	git_reference_free(ref);
+
+	git_buf_free(&log_path);
+}
+
+void test_refs_reflog_reflog__fails_gracefully_on_nonempty_reflog_dir(void)
+{
+	git_reference *ref;
+	git_buf log_path = GIT_BUF_INIT;
+	git_oid id;
+
+	/* Create a new branch pointing at the HEAD */
+	git_oid_fromstr(&id, current_master_tip);
+	cl_git_pass(git_reference_create(&ref, g_repo, "refs/heads/new-dir/new-head", &id, 0, NULL));
+	git_reference_free(ref);
+
+	git_buf_joinpath(&log_path, git_repository_path(g_repo), GIT_REFLOG_DIR);
+	git_buf_joinpath(&log_path, git_buf_cstr(&log_path), "refs/heads/new-dir/new-head");
+
+	cl_assert_equal_i(true, git_path_isfile(git_buf_cstr(&log_path)));
+
+	/* delete the ref manually, leave the reflog */
+	cl_must_pass(p_unlink("testrepo.git/refs/heads/new-dir/new-head"));
+
+	/* new ref creation should fail since new-dir contains reflogs still */
+	git_oid_fromstr(&id, current_master_tip);
+	cl_git_fail_with(GIT_EDIRECTORY, git_reference_create(&ref, g_repo, "refs/heads/new-dir", &id, 0, NULL));
+	git_reference_free(ref);
+
+	git_buf_free(&log_path);
+}
+
 static void assert_has_reflog(bool expected_result, const char *name)
 {
 	cl_assert_equal_i(expected_result, git_reference_has_log(g_repo, name));