git-remote show: Also shorten non-fast-forward refs in the 'push' listing

git-remote show: Also shorten non-fast-forward refs in the 'push' listing

'git-remote show remote-name' lists the refs that are pushed to the remote
by showing the 'Push' line from the config file. But before showing it,
it shortened 'refs/heads/here:refs/heads/there' to 'here:there'. However,
if the Push line is prefixed with a plus, the ref was not shortened.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>