worktree.c: store "id" instead of "git_dir"

We can reconstruct git_dir from id quite easily. It's a bit hackier to
do the reverse.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

branch.c

@@ -357,7 +357,8 @@ int replace_each_worktree_head_symref(const char *oldref, const char *newref)
 		if (strcmp(oldref, worktrees[i]->head_ref))
 			continue;
 
-		if (set_worktree_head_symref(worktrees[i]->git_dir, newref)) {
+		if (set_worktree_head_symref(get_worktree_git_dir(worktrees[i]),
+					     newref)) {
 			ret = -1;
 			error(_("HEAD of working tree %s is not updated"),
 			      worktrees[i]->path);

worktree.c

@@ -9,7 +9,7 @@ void free_worktrees(struct worktree **worktrees)
 
 	for (i = 0; worktrees[i]; i++) {
 		free(worktrees[i]->path);
-		free(worktrees[i]->git_dir);
+		free(worktrees[i]->id);
 		free(worktrees[i]->head_ref);
 		free(worktrees[i]);
 	}
@@ -74,13 +74,11 @@ static struct worktree *get_main_worktree(void)
 	struct worktree *worktree = NULL;
 	struct strbuf path = STRBUF_INIT;
 	struct strbuf worktree_path = STRBUF_INIT;
-	struct strbuf gitdir = STRBUF_INIT;
 	struct strbuf head_ref = STRBUF_INIT;
 	int is_bare = 0;
 	int is_detached = 0;
 
-	strbuf_addf(&gitdir, "%s", absolute_path(get_git_common_dir()));
-	strbuf_addbuf(&worktree_path, &gitdir);
+	strbuf_addstr(&worktree_path, absolute_path(get_git_common_dir()));
 	is_bare = !strbuf_strip_suffix(&worktree_path, "/.git");
 	if (is_bare)
 		strbuf_strip_suffix(&worktree_path, "/.");
@@ -92,7 +90,7 @@ static struct worktree *get_main_worktree(void)
 
 	worktree = xmalloc(sizeof(struct worktree));
 	worktree->path = strbuf_detach(&worktree_path, NULL);
-	worktree->git_dir = strbuf_detach(&gitdir, NULL);
+	worktree->id = NULL;
 	worktree->is_bare = is_bare;
 	worktree->head_ref = NULL;
 	worktree->is_detached = is_detached;
@@ -100,7 +98,6 @@ static struct worktree *get_main_worktree(void)
 
 done:
 	strbuf_release(&path);
-	strbuf_release(&gitdir);
 	strbuf_release(&worktree_path);
 	strbuf_release(&head_ref);
 	return worktree;
@@ -111,16 +108,13 @@ static struct worktree *get_linked_worktree(const char *id)
 	struct worktree *worktree = NULL;
 	struct strbuf path = STRBUF_INIT;
 	struct strbuf worktree_path = STRBUF_INIT;
-	struct strbuf gitdir = STRBUF_INIT;
 	struct strbuf head_ref = STRBUF_INIT;
 	int is_detached = 0;
 
 	if (!id)
 		die("Missing linked worktree name");
 
-	strbuf_addf(&gitdir, "%s/worktrees/%s",
-			absolute_path(get_git_common_dir()), id);
-	strbuf_addf(&path, "%s/gitdir", gitdir.buf);
+	strbuf_git_common_path(&path, "worktrees/%s/gitdir", id);
 	if (strbuf_read_file(&worktree_path, path.buf, 0) <= 0)
 		/* invalid gitdir file */
 		goto done;
@@ -140,7 +134,7 @@ static struct worktree *get_linked_worktree(const char *id)
 
 	worktree = xmalloc(sizeof(struct worktree));
 	worktree->path = strbuf_detach(&worktree_path, NULL);
-	worktree->git_dir = strbuf_detach(&gitdir, NULL);
+	worktree->id = xstrdup(id);
 	worktree->is_bare = 0;
 	worktree->head_ref = NULL;
 	worktree->is_detached = is_detached;
@@ -148,7 +142,6 @@ static struct worktree *get_linked_worktree(const char *id)
 
 done:
 	strbuf_release(&path);
-	strbuf_release(&gitdir);
 	strbuf_release(&worktree_path);
 	strbuf_release(&head_ref);
 	return worktree;
@@ -188,6 +181,16 @@ struct worktree **get_worktrees(void)
 	return list;
 }
 
+const char *get_worktree_git_dir(const struct worktree *wt)
+{
+	if (!wt)
+		return get_git_dir();
+	else if (!wt->id)
+		return get_git_common_dir();
+	else
+		return git_common_path("worktrees/%s", wt->id);
+}
+
 char *find_shared_symref(const char *symref, const char *target)
 {
 	char *existing = NULL;
@@ -199,7 +202,9 @@ char *find_shared_symref(const char *symref, const char *target)
 	for (i = 0; worktrees[i]; i++) {
 		strbuf_reset(&path);
 		strbuf_reset(&sb);
-		strbuf_addf(&path, "%s/%s", worktrees[i]->git_dir, symref);
+		strbuf_addf(&path, "%s/%s",
+			    get_worktree_git_dir(worktrees[i]),
+			    symref);
 
 		if (parse_ref(path.buf, &sb, NULL)) {
 			continue;

worktree.h

@@ -3,7 +3,7 @@
 
 struct worktree {
 	char *path;
-	char *git_dir;
+	char *id;
 	char *head_ref;
 	unsigned char head_sha1[20];
 	int is_detached;
@@ -22,6 +22,12 @@ struct worktree {
  */
 extern struct worktree **get_worktrees(void);
 
+/*
+ * Return git dir of the worktree. Note that the path may be relative.
+ * If wt is NULL, git dir of current worktree is returned.
+ */
+extern const char *get_worktree_git_dir(const struct worktree *wt);
+
 /*
  * Free up the memory for worktree(s)
  */