git-completion.bash: add remote.pushdefault to config list

224c217 (remote.c: introduce remote.pushdefault, 2013-04-02)
introduced the remote.pushdefault configuration variable, but forgot
to teach git-completion.bash about it.  Fix this.

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

contrib/completion/git-completion.bash

@@ -1823,6 +1823,10 @@ _git_config ()
 		__gitcomp "false true"
 		return
 		;;
+	remote.pushdefault)
+		__gitcomp_nl "$(__git_remotes)"
+		return
+		;;
 	remote.*.fetch)
 		local remote="${prev#remote.}"
 		remote="${remote%.fetch}"
@@ -2202,6 +2206,7 @@ _git_config ()
 		receive.fsckObjects
 		receive.unpackLimit
 		receive.updateserverinfo
+		remote.pushdefault
 		remotes.
 		repack.usedeltabaseoffset
 		rerere.autoupdate