Re: [PATCH] format-patch: cancel useAutoBase if base is invalid

Junio C Hamano [off-list ref] writes:

If we are doing the usual "prime with configuration variables and
then override from the commnad line option" thing, then you cannot
tell these two cases apart, but I happen to think that it is better
to fail (and not to ignore silently) consistently whether the
"compute an appropriate base automatically" came from config or
command line, so...

If we really need to tell these two apart, we'd invent a new
variable (we only need a single bit) to record "did we get this base
setting from the command line?" along with what we are already
doing.  You would need to use a option callback instead of a simple
OPT_STRING() to parse the "base" option, but I think it should be
straightforward.