worktree remove: allow it when $GIT_WORK_TREE is already gone

"git worktree remove" basically consists of two things

- delete $GIT_WORK_TREE
- delete $GIT_DIR (which is $SUPER_GIT_DIR/worktrees/something)

If $GIT_WORK_TREE is already gone for some reason, we should be able
to finish the job by deleting $GIT_DIR.

Two notes:

- $GIT_WORK_TREE _can_ be missing if the worktree is locked. In that
  case we must not delete $GIT_DIR because the real $GIT_WORK_TREE may
  be in a usb stick somewhere. This is already handled because we
  check for lock first.

- validate_worktree() is still called because it may do more checks in
  future (and it already does something else, like checking main
  worktree, but that's irrelevant in this case)

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

builtin/worktree.c

@@ -674,7 +674,7 @@ static int move_worktree(int ac, const char **av, const char *prefix)
 			    reason);
 		die(_("cannot move a locked working tree"));
 	}
-	if (validate_worktree(wt, &errmsg))
+	if (validate_worktree(wt, &errmsg, 0))
 		die(_("validation failed, cannot move working tree: %s"),
 		    errmsg.buf);
 	strbuf_release(&errmsg);
@@ -799,15 +799,17 @@ static int remove_worktree(int ac, const char **av, const char *prefix)
 			    reason);
 		die(_("cannot remove a locked working tree"));
 	}
-	if (validate_worktree(wt, &errmsg))
+	if (validate_worktree(wt, &errmsg, WT_VALIDATE_WORKTREE_MISSING_OK))
 		die(_("validation failed, cannot remove working tree: %s"),
 		    errmsg.buf);
 	strbuf_release(&errmsg);
 
-	if (!force)
-		check_clean_worktree(wt, av[0]);
+	if (file_exists(wt->path)) {
+		if (!force)
+			check_clean_worktree(wt, av[0]);
 
-	ret |= delete_git_work_tree(wt);
+		ret |= delete_git_work_tree(wt);
+	}
 	/*
 	 * continue on even if ret is non-zero, there's no going back
 	 * from here.

t/t2028-worktree-move.sh

@@ -126,4 +126,21 @@ test_expect_success 'force remove worktree with untracked file' '
 	test_path_is_missing destination
 '
 
+test_expect_success 'remove missing worktree' '
+	git worktree add to-be-gone &&
+	test -d .git/worktrees/to-be-gone &&
+	mv to-be-gone gone &&
+	git worktree remove to-be-gone &&
+	test_path_is_missing .git/worktrees/to-be-gone
+'
+
+test_expect_success 'NOT remove missing-but-locked worktree' '
+	git worktree add gone-but-locked &&
+	git worktree lock gone-but-locked &&
+	test -d .git/worktrees/gone-but-locked &&
+	mv gone-but-locked really-gone-now &&
+	test_must_fail git worktree remove gone-but-locked &&
+	test_path_is_dir .git/worktrees/gone-but-locked
+'
+
 test_done

worktree.c

@@ -267,7 +267,8 @@ static void strbuf_addf_gently(struct strbuf *buf, const char *fmt, ...)
 	va_end(params);
 }
 
-int validate_worktree(const struct worktree *wt, struct strbuf *errmsg)
+int validate_worktree(const struct worktree *wt, struct strbuf *errmsg,
+		      unsigned flags)
 {
 	struct strbuf wt_path = STRBUF_INIT;
 	char *path = NULL;
@@ -303,6 +304,12 @@ int validate_worktree(const struct worktree *wt, struct strbuf *errmsg)
 		goto done;
 	}
 
+	if (flags & WT_VALIDATE_WORKTREE_MISSING_OK &&
+	    !file_exists(wt->path)) {
+		ret = 0;
+		goto done;
+	}
+
 	if (!file_exists(wt_path.buf)) {
 		strbuf_addf_gently(errmsg, _("'%s' does not exist"), wt_path.buf);
 		goto done;

worktree.h

@@ -61,12 +61,15 @@ extern int is_main_worktree(const struct worktree *wt);
  */
 extern const char *is_worktree_locked(struct worktree *wt);
 
+#define WT_VALIDATE_WORKTREE_MISSING_OK (1 << 0)
+
 /*
  * Return zero if the worktree is in good condition. Error message is
  * returned if "errmsg" is not NULL.
  */
 extern int validate_worktree(const struct worktree *wt,
-			     struct strbuf *errmsg);
+			     struct strbuf *errmsg,
+			     unsigned flags);
 
 /*
  * Update worktrees/xxx/gitdir with the new path.