stash: fix git stash branch regression when branch creation fails

"git stash branch <branch> <stash>" started discarding the stash
when the branch creation fails.  It should have kept the stash
intact when aborting.

Signed-off-by: Jon Seymour <jon.seymour@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-stash.sh

@@ -446,9 +446,9 @@ apply_to_branch () {
 	assert_stash_like "$@"
 
 	git checkout -b $branch $REV^ &&
-	apply_stash "$@"
-
-	test -z "$IS_STASH_REF" || drop_stash "$@"
+	apply_stash "$@" && {
+		test -z "$IS_STASH_REF" || drop_stash "$@"
+	}
 }
 
 PARSE_CACHE='--not-parsed'

t/t3903-stash.sh

@@ -545,7 +545,7 @@ test_expect_success 'invalid ref of the form stash@{n}, n >= N' '
 	git stash drop
 '
 
-test_expect_failure 'stash branch should not drop the stash if the branch exists' '
+test_expect_success 'stash branch should not drop the stash if the branch exists' '
 	git stash clear &&
 	echo foo >file &&
 	git add file &&