reflog: keep the reflog name in sync with the reference name

src/reflog.c

@@ -183,6 +183,18 @@ static int retrieve_reflog_path(git_buf *path, git_reference *ref)
 		git_reference_owner(ref)->path_repository, GIT_REFLOG_DIR, ref->name);
 }
 
+int create_new_reflog_file(const char *filepath)
+{
+	int fd;
+
+	if ((fd = p_open(filepath,
+			O_WRONLY | O_CREAT | O_TRUNC,
+			GIT_REFLOG_FILE_MODE)) < 0)
+		return -1;
+
+	return p_close(fd);
+}
+
 int git_reflog_read(git_reflog **reflog, git_reference *ref)
 {
 	int error;
@@ -204,6 +216,10 @@ int git_reflog_read(git_reflog **reflog, git_reference *ref)
 	if (error < 0 && error != GIT_ENOTFOUND)
 		goto cleanup;
 
+	if ((error == GIT_ENOTFOUND) &&
+		((error = create_new_reflog_file(git_buf_cstr(&log_path))) < 0))
+		goto cleanup;
+
 	if ((error = reflog_parse(log,
 		git_buf_cstr(&log_file), git_buf_len(&log_file))) < 0)
 		goto cleanup;
@@ -237,6 +253,12 @@ int git_reflog_write(git_reflog *reflog)
 		git_repository_path(reflog->owner), GIT_REFLOG_DIR, reflog->ref_name) < 0)
 		return -1;
 
+	if (!git_path_isfile(git_buf_cstr(&log_path))) {
+		giterr_set(GITERR_INVALID,
+			"Log file for reference '%s' doesn't exist.", reflog->ref_name);
+		goto cleanup;
+	}
+
 	if ((error = git_filebuf_open(&fbuf, git_buf_cstr(&log_path), 0)) < 0)
 		goto cleanup;
 

tests-clar/refs/reflog/reflog.c

@@ -149,3 +149,24 @@ void test_refs_reflog_reflog__reading_the_reflog_from_a_reference_with_no_log_re
 	git_reference_free(subtrees);
 	git_buf_free(&subtrees_log_path);
 }
+
+void test_refs_reflog_reflog__cannot_write_a_moved_reflog(void)
+{
+	git_reference *master;
+	git_buf master_log_path = GIT_BUF_INIT, moved_log_path = GIT_BUF_INIT;
+	git_reflog *reflog;
+
+	cl_git_pass(git_reference_lookup(&master, g_repo, "refs/heads/master"));
+	cl_git_pass(git_reflog_read(&reflog, master));
+
+	cl_git_pass(git_reflog_write(reflog));
+	
+	cl_git_pass(git_reference_rename(master, "refs/moved", 0));
+
+	cl_git_fail(git_reflog_write(reflog));
+
+	git_reflog_free(reflog);
+	git_reference_free(master);
+	git_buf_free(&moved_log_path);
+	git_buf_free(&master_log_path);
+}