As suggested in issue1025, an alternative solution would be to have a
'local_darcs' preference in the remote repository telling anyone interacting
with that repo how to call darcs on this machine.

This way, if on my machine I have darcs installed in /some/funky/path/darcs-sfx,
I can just set local_darcs to that path. Anyone pushing to my repository will
execute this command.

If flag proliferation is a problem, instead of a flag, include it in the url
scheme, like so: 'darcs push toto@machine:/repo#darcs-command'. This way, it can
be saved in the repos file, and persist between session.