get_worktrees() must return main worktree as first item even on error

This is required by git-worktree.txt, stating that the main worktree is
the first line (especially in --porcelain mode when we can't just change
behavior at will).

There's only one case when get_worktrees() may skip main worktree, when
parse_ref() fails. Update the code so that we keep first item as main
worktree and return something sensible in this case:

 - In user-friendly mode, since we're not constraint by anything,
   returning "(error)" should do the job (we already show "(detached
   HEAD)" which is not machine-friendly). Actually errors should be
   printed on stderr by parse_ref() (*)

 - In plumbing mode, we do not show neither 'bare', 'detached' or
   'branch ...', which is possible by the format description if I read
   it right.

Careful readers may realize that when the local variable "head_ref" in
get_main_worktree() is emptied, add_head_info() will do nothing to
wt->head_sha1. But that's ok because head_sha1 is zero-ized in the
previous patch.

(*) Well, it does not. But it's supposed to be a stop gap implementation
    until we can reuse refs code to parse "ref: " stuff in HEAD, from
    resolve_refs_unsafe(). Now may be the time since refs refactoring is
    mostly done.

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

1 files changed, 3 insertions, 7 deletions

diff --git a/worktree.c b/worktree.c
index f7c1b5e24d..3145522536 100644
--- a/worktree.c
+++ b/worktree.c
@@ -88,16 +88,13 @@ static struct worktree *get_main_worktree(void)
 
 	strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
 
-	if (parse_ref(path.buf, &head_ref, &is_detached) < 0)
-		goto done;
-
 	worktree = xcalloc(1, sizeof(*worktree));
 	worktree->path = strbuf_detach(&worktree_path, NULL);
 	worktree->is_bare = is_bare;
 	worktree->is_detached = is_detached;
-	add_head_info(&head_ref, worktree);
+	if (!parse_ref(path.buf, &head_ref, &is_detached))
+		add_head_info(&head_ref, worktree);
 
-done:
 	strbuf_release(&path);
 	strbuf_release(&worktree_path);
 	strbuf_release(&head_ref);
@@ -173,8 +170,7 @@ struct worktree **get_worktrees(void)
 
 	list = xmalloc(alloc * sizeof(struct worktree *));
 
-	if ((list[counter] = get_main_worktree()))
-		counter++;
+	list[counter++] = get_main_worktree();
 
 	strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
 	dir = opendir(path.buf);