completion: complete show-branch "--date-order"

Signed-off-by: Paul Wagland <paul@kungfoocoder.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Paul Wagland

contrib/completion/git-completion.bash

@@ -2368,7 +2368,7 @@ _git_show_branch ()
 	case "$cur" in
 	--*)
 		__gitcomp "
-			--all --remotes --topo-order --current --more=
+			--all --remotes --topo-order --date-order --current --more=
 			--list --independent --merge-base --no-name
 			--color --no-color
 			--sha1-name --sparse --topics --reflog