builtin/worktree: create refdb via ref backend

When creating a worktree we create the worktree's ref database manually
by first writing a "HEAD" file so that the directory is recognized as a
Git repository by other commands, and then running git-update-ref(1) or
git-symbolic-ref(1) to write the actual value. But while this is fine
for the files backend, this logic simply assumes too much about how the
ref backend works and will leave behind an invalid ref database once any
other ref backend lands.

Refactor the code to instead use `refs_init_db()` to initialize the ref
database so that git-worktree(1) itself does not need to know about how
to initialize it. This will allow future ref backends to customize how
the per-worktree ref database is set up. Furthermore, as we now already
have a worktree ref store around, we can also avoid spawning external
commands to write the HEAD reference and instead use the refs API to do
so.

Note that we do not have an equivalent to passing the `--quiet` flag to
git-symbolic-ref(1) as we did before. This flag does not have an effect
anyway though, as git-symbolic-ref(1) only honors it when reading a
symref, but never when writing one.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/worktree.c

@@ -416,15 +416,15 @@ static int add_worktree(const char *path, const char *refname,
 	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT, realpath = STRBUF_INIT;
 	const char *name;
-	struct child_process cp = CHILD_PROCESS_INIT;
 	struct strvec child_env = STRVEC_INIT;
 	unsigned int counter = 0;
 	int len, ret;
 	struct strbuf symref = STRBUF_INIT;
 	struct commit *commit = NULL;
 	int is_branch = 0;
 	struct strbuf sb_name = STRBUF_INIT;
-	struct worktree **worktrees;
+	struct worktree **worktrees, *wt = NULL;
+	struct ref_store *wt_refs;
 
 	worktrees = get_worktrees();
 	check_candidate_path(path, opts->force, worktrees, "add");
@@ -500,15 +500,26 @@ static int add_worktree(const char *path, const char *refname,
 	write_file(sb.buf, "../..");
 
 	/*
-	 * This is to keep resolve_ref() happy. We need a valid HEAD
-	 * or is_git_directory() will reject the directory. Any value which
-	 * looks like an object ID will do since it will be immediately
-	 * replaced by the symbolic-ref or update-ref invocation in the new
-	 * worktree.
+	 * Set up the ref store of the worktree and create the HEAD reference.
 	 */
-	strbuf_reset(&sb);
-	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
-	write_file(sb.buf, "%s", oid_to_hex(null_oid()));
+	wt = get_linked_worktree(name, 1);
+	if (!wt) {
+		ret = error(_("could not find created worktree '%s'"), name);
+		goto done;
+	}
+	wt_refs = get_worktree_ref_store(wt);
+
+	ret = refs_init_db(wt_refs, REFS_INIT_DB_IS_WORKTREE, &sb);
+	if (ret)
+		goto done;
+
+	if (!is_branch && commit)
+		ret = refs_update_ref(wt_refs, NULL, "HEAD", &commit->object.oid,
+				      NULL, 0, UPDATE_REFS_MSG_ON_ERR);
+	else
+		ret = refs_create_symref(wt_refs, "HEAD", symref.buf, NULL);
+	if (ret)
+		goto done;
 
 	/*
 	 * If the current worktree has sparse-checkout enabled, then copy
@@ -527,22 +538,6 @@ static int add_worktree(const char *path, const char *refname,
 
 	strvec_pushf(&child_env, "%s=%s", GIT_DIR_ENVIRONMENT, sb_git.buf);
 	strvec_pushf(&child_env, "%s=%s", GIT_WORK_TREE_ENVIRONMENT, path);
-	cp.git_cmd = 1;
-
-	if (!is_branch && commit) {
-		strvec_pushl(&cp.args, "update-ref", "HEAD",
-			     oid_to_hex(&commit->object.oid), NULL);
-	} else {
-		strvec_pushl(&cp.args, "symbolic-ref", "HEAD",
-			     symref.buf, NULL);
-		if (opts->quiet)
-			strvec_push(&cp.args, "--quiet");
-	}
-
-	strvec_pushv(&cp.env, child_env.v);
-	ret = run_command(&cp);
-	if (ret)
-		goto done;
 
 	if (opts->orphan &&
 	    (ret = make_worktree_orphan(refname, opts, &child_env)))
@@ -588,6 +583,7 @@ static int add_worktree(const char *path, const char *refname,
 	strbuf_release(&sb_git);
 	strbuf_release(&sb_name);
 	strbuf_release(&realpath);
+	free_worktree(wt);
 	return ret;
 }