quoted

and that even without
setting the variables, "git cherry-pick" will pick a new commit date but
"git cherry-pick --ff" wouldn't.  The latter, I think is the only
difference that is worth pondering further.

Because --no-ff could be used when the GIT_COMMITTER_* and GIT_AUTHOR_* env
variable should be respected? Or because we should check if one of these
env variable is set and, if that is the case, we should not fast forward?

I wish it could be the former, at least in the long run; after all git 
merge fast-forwards by default, and it doesn't adjust its behavior if 
GIT_COMMITTER_* is passed.

Anyway, your plan of starting with --ff and changing the default to 
--no-ff later seems fine.  Maybe you can add --no-ff now already, though 
it would be a no-op.

quoted

Note that "-e --ff" would error out; however if --ff would be the
default, "-e" would probably choose between fast-forward and
non-fast-forward depending on whether the commit message was edited.

Yeah, but let's change the default later please.

Sure.

Paolo