mq: support "qimport --existing --name renametothis thatexistingpatch"
Before this change, the command would abort with a not too clear "patch
renametothis does not exist" error.
This change makes:
qimport --existing --name renametothis thatexistingpatch
equivalent to:
qimport --existing thatexistingpatch; qrename thatexistingpatch renametothis
% inserve
A dir/c
? a
? dir/b
? hg.pid
% moving dir out
% status
! dir/c
? a
? hg.pid
Are we able to kill the service? if not, the service died on some error