completion: fix remote.pushdefault

When attempting to complete

  $ git config remote.push<TAB>

'pushdefault' doesn't come up. This is because "$cur" is matched with
"remote.*" and a list of remotes are completed. Add 'pushdefault' as a
candidate for completion too, using __gitcomp_nl_append ().

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -1884,6 +1884,7 @@ _git_config ()
 	remote.*)
 		local pfx="${cur%.*}." cur_="${cur#*.}"
 		__gitcomp_nl "$(__git_remotes)" "$pfx" "$cur_" "."
+		__gitcomp_nl_append "pushdefault" "$pfx" "$cur_"
 		return
 		;;
 	url.*.*)