[PATCH 2/3] get_worktrees() must return main worktree as first item even on error

[Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>]

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 refs we can reuse 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@xxxxxxxxx>
---
 builtin/worktree.c | 8 +++++---
 worktree.c         | 6 ++----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/builtin/worktree.c b/builtin/worktree.c
index 5c4854d..b835b91 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -388,7 +388,7 @@ static void show_worktree_porcelain(struct worktree *wt)
 		printf("HEAD %s\n", sha1_to_hex(wt->head_sha1));
 		if (wt->is_detached)
 			printf("detached\n");
-		else
+		else if (wt->head_ref)
 			printf("branch %s\n", wt->head_ref);
 	}
 	printf("\n");
@@ -406,10 +406,12 @@ static void show_worktree(struct worktree *wt, int path_maxlen, int abbrev_len)
 	else {
 		strbuf_addf(&sb, "%-*s ", abbrev_len,
 				find_unique_abbrev(wt->head_sha1, DEFAULT_ABBREV));
-		if (!wt->is_detached)
+		if (wt->is_detached)
+			strbuf_addstr(&sb, "(detached HEAD)");
+		else if (wt->head_ref)
 			strbuf_addf(&sb, "[%s]", shorten_unambiguous_ref(wt->head_ref, 0));
 		else
-			strbuf_addstr(&sb, "(detached HEAD)");
+			strbuf_addstr(&sb, "(error)");
 	}
 	printf("%s\n", sb.buf);
 
diff --git a/worktree.c b/worktree.c
index f7c1b5e..a674efa 100644
--- a/worktree.c
+++ b/worktree.c
@@ -89,7 +89,7 @@ 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;
+		strbuf_reset(&head_ref);
 
 	worktree = xcalloc(1, sizeof(*worktree));
 	worktree->path = strbuf_detach(&worktree_path, NULL);
@@ -97,7 +97,6 @@ static struct worktree *get_main_worktree(void)
 	worktree->is_detached = is_detached;
 	add_head_info(&head_ref, worktree);
 
-done:
 	strbuf_release(&path);
 	strbuf_release(&worktree_path);
 	strbuf_release(&head_ref);
@@ -173,8 +172,7 @@ 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);
-- 
2.8.2.524.g6ff3d78