git-completion.bash: add completion for stash list

Since stash list accepts git-log options, add the following useful
options that make sense in the context of the `git stash list` command:

  --name-status --oneline --patch-with-stat

Signed-off-by: Steven Fernandez <steve@lonetwin.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2567,6 +2567,9 @@ _git_stash ()
 		drop,--*)
 			__gitcomp "--quiet"
 			;;
+		list,--*)
+			__gitcomp "--name-status --oneline --patch-with-stat"
+			;;
 		show,--*|branch,--*)
 			;;
 		branch,*)