[RFC PATCH] status: avoid reporting worktrees as "Untracked files"

[Edmundo Carmona Antoranz <eantoranz@gmail.com>]

Given that worktrees are tracked in their own special fashion separately,
it makes sense to _not_ report them as "untracked". Also, when seeing the
directory of a worktree listed as Untracked, it might be tempting to try
to do operations (like 'git add') on them from the parent worktree which,
at the moment, will silently do nothing.

With this patch, we check items against the list of worktrees to add
them into the untracked items list effectively hiding them.

END OF PATCH

Here are a few questions more inline with the "RFC" part of the patch.

About UI
- Would it make more sense to separate them from Untracked files instead
  of hiding them (perhaps add a --worktrees option to display them)?
- Follow-up if the previous answer is 'yes': List a worktree only if it
  is not clean?

About code:
- If keeping the idea/patch, Would it make more sense (performance-wise) to
  fist check an item in the list of worktrees before checking it in the
  index? In other words, reverse the conditions to add an item to the
  untracked list?
---
 wt-status.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/wt-status.c b/wt-status.c
index 9f45bf6949..5fd1e6007a 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -775,6 +775,7 @@ static void wt_status_collect_untracked(struct wt_status *s)
 	struct dir_struct dir = DIR_INIT;
 	uint64_t t_begin = getnanotime();
 	struct index_state *istate = s->repo->index;
+	struct worktree **worktrees;
 
 	if (!s->show_untracked_files)
 		return;
@@ -795,9 +796,12 @@ static void wt_status_collect_untracked(struct wt_status *s)
 
 	fill_directory(&dir, istate, &s->pathspec);
 
+	worktrees = get_worktrees();
+
 	for (i = 0; i < dir.nr; i++) {
 		struct dir_entry *ent = dir.entries[i];
-		if (index_name_is_other(istate, ent->name, ent->len))
+		if (index_name_is_other(istate, ent->name, ent->len) &&
+		    !find_worktree_by_path(worktrees, ent->name))
 			string_list_insert(&s->untracked, ent->name);
 	}
 
@@ -809,6 +813,9 @@ static void wt_status_collect_untracked(struct wt_status *s)
 
 	dir_clear(&dir);
 
+	if (worktrees)
+		free_worktrees(worktrees);
+
 	if (advice_enabled(ADVICE_STATUS_U_OPTION))
 		s->untracked_in_ms = (getnanotime() - t_begin) / 1000000;
 }
-- 
2.42.0