worktree: teach 'add' to respect --force for registered but missing path

For safety, "git worktree add <path>" will refuse to add a new
worktree at <path> if <path> is already associated with a worktree
entry, even if <path> is missing (for instance, has been deleted or
resides on non-mounted removable media or network share). The typical
way to re-create a worktree at <path> in such a situation is either to
prune all "broken" entries ("git worktree prune") or to selectively
remove the worktree entry manually ("git worktree remove <path>").

However, neither of these approaches ("prune" nor "remove") is
especially convenient, and they may be unsuitable for scripting when a
tool merely wants to re-use a worktree if it exists or create it from
scratch if it doesn't (much as a tool might use "mkdir -p" to re-use
or create a directory).

Therefore, teach 'add' to respect --force as a convenient way to
re-use a path already associated with a worktree entry if the path is
non-existent. For a locked worktree, require --force to be specified
twice.

Signed-off-by: Eric Sunshine <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: sunshineco

Documentation/git-worktree.txt

@@ -120,8 +120,12 @@ OPTIONS
 --force::
 	By default, `add` refuses to create a new working tree when
 	`<commit-ish>` is a branch name and is already checked out by
-	another working tree and `remove` refuses to remove an unclean
-	working tree. This option overrides these safeguards.
+	another working tree, or if `<path>` is already assigned to some
+	working tree but is missing (for instance, if `<path>` was deleted
+	manually). This option overrides these safeguards. To add a missing but
+	locked working tree path, specify `--force` twice.
++
+`remove` refuses to remove an unclean working tree unless `--force` is used.
 
 -b <new-branch>::
 -B <new-branch>::

builtin/worktree.c

@@ -241,10 +241,16 @@ static void validate_worktree_add(const char *path, const struct add_opts *opts)
 		goto done;
 
 	locked = !!is_worktree_locked(wt);
+	if ((!locked && opts->force) || (locked && opts->force > 1)) {
+		if (delete_git_dir(wt->id))
+		    die(_("unable to re-add worktree '%s'"), path);
+		goto done;
+	}
+
 	if (locked)
-		die(_("'%s' is a missing but locked worktree;\nuse 'unlock' and 'prune' or 'remove' to clear"), path);
+		die(_("'%s' is a missing but locked worktree;\nuse 'add -f -f' to override, or 'unlock' and 'prune' or 'remove' to clear"), path);
 	else
-		die(_("'%s' is a missing but already registered worktree;\nuse 'prune' or 'remove' to clear"), path);
+		die(_("'%s' is a missing but already registered worktree;\nuse 'add -f' to override, or 'prune' or 'remove' to clear"), path);
 
 done:
 	free_worktrees(worktrees);

t/t2025-worktree-add.sh

@@ -556,7 +556,18 @@ test_expect_success '"add" an existing but missing worktree' '
 	git worktree add --detach pneu &&
 	test_must_fail git worktree add --detach pneu &&
 	rm -fr pneu &&
-	test_must_fail git worktree add --detach pneu
+	test_must_fail git worktree add --detach pneu &&
+	git worktree add --force --detach pneu
+'
+
+test_expect_success '"add" an existing locked but missing worktree' '
+	git worktree add --detach gnoo &&
+	git worktree lock gnoo &&
+	test_when_finished "git worktree unlock gnoo || :" &&
+	rm -fr gnoo &&
+	test_must_fail git worktree add --detach gnoo &&
+	test_must_fail git worktree add --force --detach gnoo &&
+	git worktree add --force --force --detach gnoo
 '
 
 test_done