Wesley Schwengle [off-list ref] writes:

I like the idea of the warning, but it could be loud indeed and you'll
want to turn it off in that case.

I tend to think that a single-liner warning would not be too
intrusive (it might actually be too subtle to be noticed),
especially given that it is issued only when the fork-point does
move the target commit from what was given.

Giving a shortlog of what is lost in the history does sound like a
bit too loud, I am afraind, though.