David Kastrup [off-list ref] writes:
I get
Option -m cannot be combined with -c/-C/-F/--amend.
but that makes no sense: of course there is ample reason for providing
an amended commit message on the command line. -c, -C and -F indeed
all provide an alternative commit message, but --amend doesn't.
The option --amend is about "reusing the original commit message
and make amending edit on top". If you are restarting the
message from scratch, --amend does not make much sense.
You can do:
$ git reset HEAD^
$ git commit -m "blah"
if you do not want to reuse the commit message.