tg-push: prevent handing branches more than once to git-push

tg-push: prevent handing branches more than once to git-push

Doing otherwise can result in a lot of warnings and errors:

	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master
	warning, no base found top-bases/master

	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/master is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/master
	error: Ref refs/heads/bw/log is at a16df35cc7009b36f6f71717ae3d9a3dc29987da but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/heads/bw/log
	error: Ref refs/top-bases/bw/log is at b725fc951a37854fc65945ac5bcab3bc61ccbd94 but expected 0000000000000000000000000000000000000000
	error: failed to lock refs/top-bases/bw/log

	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] master -> master (failed to lock)
	 ! [remote rejected] bw/log -> bw/log (failed to lock)
	 ! [remote rejected] refs/top-bases/bw/log -> refs/top-bases/bw/log (failed to lock)

Note, the result is OK only the output is irritating.

Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>