stash: pass the pathspec argument to git reset

For "git stash -p --no-keep-index", the pathspec argument is currently
not passed to "git reset".  This means that changes that are staged but
that are excluded from the pathspec still get unstaged by git stash -p.

Make sure that doesn't happen by passing the pathspec argument to the
git reset in question, bringing the behaviour in line with "git stash --
<pathspec>".

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-stash.sh

@@ -322,7 +322,7 @@ push_stash () {
 
 		if test "$keep_index" != "t"
 		then
-			git reset -q
+			git reset -q -- "$@"
 		fi
 	fi
 }

t/t3904-stash-patch.sh

@@ -77,6 +77,14 @@ test_expect_success 'git stash --no-keep-index -p' '
 	verify_state dir/foo work index
 '
 
+test_expect_success 'stash -p --no-keep-index -- <pathspec> does not unstage other files' '
+	set_state HEAD HEADfile_work HEADfile_index &&
+	set_state dir/foo work index &&
+	echo y | git stash push -p --no-keep-index -- HEAD &&
+	verify_state HEAD committed committed &&
+	verify_state dir/foo work index
+'
+
 test_expect_success 'none of this moved HEAD' '
 	verify_saved_head
 '