git-p4: support updating an existing shelved changelist
Adds new option "--update-shelve CHANGELIST" which updates
an existing shelved changelist.
The original changelist must have been created by the current user.
This allows workflow something like:
hack hack hack
git commit
git p4 submit --shelve
$mail interested parties about shelved changelist
make corrections
git commit --amend
git p4 submit --update-shelve $CHANGELIST
$mail interested parties about shelved changelist
etc
Signed-off-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>