stash: do not attempt to remove startup_info->original_cwd

Since stash spawns a `clean` subprocess, make sure we run that from the
startup_info->original_cwd directory, so that the `clean` processs knows
to protect that directory.  Also, since the `clean` command might no
longer run from the toplevel, pass the ':/' magic pathspec to ensure we
still clean from the toplevel.

Acked-by: Derrick Stolee <[email protected]>
Acked-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

builtin/stash.c

@@ -1485,8 +1485,10 @@ static int do_push_stash(const struct pathspec *ps, const char *stash_msg, int q
 			struct child_process cp = CHILD_PROCESS_INIT;
 
 			cp.git_cmd = 1;
+			if (startup_info->original_cwd)
+				cp.dir = startup_info->original_cwd;
 			strvec_pushl(&cp.args, "clean", "--force",
-				     "--quiet", "-d", NULL);
+				     "--quiet", "-d", ":/", NULL);
 			if (include_untracked == INCLUDE_ALL_FILES)
 				strvec_push(&cp.args, "-x");
 			if (run_command(&cp)) {

t/t2501-cwd-empty.sh

@@ -236,7 +236,7 @@ test_expect_success 'clean does not remove cwd incidentally' '
 '
 
 test_expect_success 'stash does not remove cwd incidentally' '
-	test_incidental_untracked_dir_removal failure \
+	test_incidental_untracked_dir_removal success \
 		git stash --include-untracked
 '