stash: ensure --no-keep-index and --patch can be used in any order

Don't assume one comes after the other on the command line. Use a
three-state variable to track and check its value accordingly.

Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-stash.sh

@@ -136,11 +136,12 @@ save_stash () {
 			keep_index=t
 			;;
 		--no-keep-index)
-			keep_index=
+			keep_index=n
 			;;
 		-p|--patch)
 			patch_mode=t
-			keep_index=t
+			# only default to keep if we don't already have an override
+			test -z "$keep_index" && keep_index=t
 			;;
 		-q|--quiet)
 			GIT_QUIET=t
@@ -185,15 +186,15 @@ save_stash () {
 	then
 		git reset --hard ${GIT_QUIET:+-q}
 
-		if test -n "$keep_index" && test -n $i_tree
+		if test "$keep_index" = "t" && test -n $i_tree
 		then
 			git read-tree --reset -u $i_tree
 		fi
 	else
 		git apply -R < "$TMP-patch" ||
 		die "Cannot remove worktree changes"
 
-		if test -z "$keep_index"
+		if test "$keep_index" != "t"
 		then
 			git reset
 		fi

t/t3904-stash-patch.sh

@@ -48,7 +48,7 @@ test_expect_success PERL 'git stash -p --no-keep-index' '
 	verify_state bar dummy bar_index
 '
 
-test_expect_failure PERL 'git stash --no-keep-index -p' '
+test_expect_success PERL 'git stash --no-keep-index -p' '
 	set_state dir/foo work index &&
 	set_state bar bar_work bar_index &&
 	(echo n; echo y) | git stash save --no-keep-index -p &&