[PATCH] worktree: teach find_shared_symref to ignore current worktree

[Rubén Justo <rjusto@xxxxxxxxx>]

We prevent some operations from being executed on a branch checked out
in a worktree other than the current one.  An example of this was
introduced in b5cabb4 (rebase: refuse to switch to branch already
checked out elsewhere, 2020-02-23).

"find_shared_symref()" is sometimes used to find the worktree in which a
branch is checked out.  It performs its search starting with the current
worktree.

As we allow to have the same branch checked out in multiple worktrees
simultaneously...

	$ git worktree add foo
	$ git worktree add -f bar foo
	$ git checkout --ignore-other-worktrees foo

... if the branch checked out in the current worktree is also checked
out in another worktree, with "find_shared_symref()" we will not notice
this "other" working tree.

Let's teach "find_shared_symref()" to ignore the current worktree in the
search, based on the caller's needs.

Signed-off-by: Rubén Justo <rjusto@xxxxxxxxx>
---
 branch.c               | 4 ++--
 builtin/notes.c        | 2 +-
 builtin/receive-pack.c | 2 +-
 t/t3400-rebase.sh      | 3 +++
 worktree.c             | 6 +++++-
 worktree.h             | 3 ++-
 6 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/branch.c b/branch.c
index d182756827..2508e94add 100644
--- a/branch.c
+++ b/branch.c
@@ -822,8 +822,8 @@ void die_if_checked_out(const char *branch, int ignore_current_worktree)
 	struct worktree **worktrees = get_worktrees();
 	const struct worktree *wt;
 
-	wt = find_shared_symref(worktrees, "HEAD", branch);
-	if (wt && (!ignore_current_worktree || !wt->is_current)) {
+	wt = find_shared_symref(worktrees, "HEAD", branch, ignore_current_worktree);
+	if (wt) {
 		skip_prefix(branch, "refs/heads/", &branch);
 		die(_("'%s' is already checked out at '%s'"), branch, wt->path);
 	}
diff --git a/builtin/notes.c b/builtin/notes.c
index 80d9dfd25c..80326bdaab 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -869,7 +869,7 @@ static int merge(int argc, const char **argv, const char *prefix)
 		/* Store ref-to-be-updated into .git/NOTES_MERGE_REF */
 		worktrees = get_worktrees();
 		wt = find_shared_symref(worktrees, "NOTES_MERGE_REF",
-					default_notes_ref());
+					default_notes_ref(), 0);
 		if (wt)
 			die(_("a notes merge into %s is already in-progress at %s"),
 			    default_notes_ref(), wt->path);
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index a90af30363..18d400101c 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1460,7 +1460,7 @@ static const char *update(struct command *cmd, struct shallow_info *si)
 	int do_update_worktree = 0;
 	struct worktree **worktrees = get_worktrees();
 	const struct worktree *worktree =
-		find_shared_symref(worktrees, "HEAD", name);
+		find_shared_symref(worktrees, "HEAD", name, 0);
 
 	/* only refs/... are allowed */
 	if (!starts_with(name, "refs/") || check_refname_format(name + 5, 0)) {
diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
index d5a8ee39fc..874cfff8fe 100755
--- a/t/t3400-rebase.sh
+++ b/t/t3400-rebase.sh
@@ -407,6 +407,9 @@ test_expect_success 'refuse to switch to branch checked out elsewhere' '
 	git checkout main &&
 	git worktree add wt &&
 	test_must_fail git -C wt rebase main main 2>err &&
+	test_i18ngrep "already checked out" err &&
+	git worktree add --force wt2 main &&
+	test_must_fail git rebase main main &&
 	test_i18ngrep "already checked out" err
 '
 
diff --git a/worktree.c b/worktree.c
index aa43c64119..3d686137ef 100644
--- a/worktree.c
+++ b/worktree.c
@@ -405,7 +405,8 @@ int is_worktree_being_bisected(const struct worktree *wt,
  */
 const struct worktree *find_shared_symref(struct worktree **worktrees,
 					  const char *symref,
-					  const char *target)
+					  const char *target,
+					  int ignore_current_worktree)
 {
 	const struct worktree *existing = NULL;
 	int i = 0;
@@ -416,6 +417,9 @@ const struct worktree *find_shared_symref(struct worktree **worktrees,
 		struct ref_store *refs;
 		int flags;
 
+		if (wt->is_current && ignore_current_worktree)
+			continue;
+
 		if (wt->is_bare)
 			continue;
 
diff --git a/worktree.h b/worktree.h
index 9dcea6fc8c..a9f35ee990 100644
--- a/worktree.h
+++ b/worktree.h
@@ -147,7 +147,8 @@ void free_worktrees(struct worktree **);
  */
 const struct worktree *find_shared_symref(struct worktree **worktrees,
 					  const char *symref,
-					  const char *target);
+					  const char *target,
+					  int ignore_current_worktree);
 
 /*
  * Similar to head_ref() for all HEADs _except_ one from the current
-- 
2.39.0