Right now, hg help graft says:
The -c/--continue option does not reapply earlier options, except for --force.
which should be treated as a bug.
A good user experience is that the commands remember the arguments passed
initially and preserve them during hg graft --continue.
This patch starts storing the user and date information in graftstate if user
passed it. Upcoming patches will make sure we preserve that information during
--continue and them don't allow user to pass any new arguments with --continue.
I don't think there is any another --continue flag which allows new options to
be passed with it.