git-checkout: allow pathspec to recover lost working tree directory

It is often wanted on the #git channel that this were to work to
recover removed directory:

	rm -fr Documentation
	git checkout -- Documentation
	git checkout HEAD -- Documentation ;# alternatively

Now it does.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-checkout.sh

@@ -112,7 +112,11 @@ Did you intend to checkout '$@' which can not be resolved as commit?"
 		git-ls-tree --full-name -r "$new" "$@" |
 		git-update-index --index-info || exit $?
 	fi
-	git-checkout-index -f -u -- "$@"
+
+	# Make sure the request is about existing paths.
+	git-ls-files --error-unmatch -- "$@" >/dev/null || exit
+	git-ls-files -- "$@" |
+	git-checkout-index -f -u --stdin
 	exit $?
 else
 	# Make sure we did not fall back on $arg^{tree} codepath