Fail git pull --rebase when local merges present? (was: [ANNOUNCE] Git v2.11.1)

[Stephen Bash]

On Thu, Feb 2, 2017 at 6:05 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote:

>  * "git pull --rebase", when there is no new commits on our side since
>    we forked from the upstream, should be able to fast-forward without
>    invoking "git rebase", but it didn't.

As someone who has to mentor new developers to Git at my $dayjob, this
is really nice!  Thanks!

Slightly related (in that it's a pitfall of *always* using pull
--rebase), does anyone know if there is a way to make git pull
--rebase fail if there's a local merge?  For our workflow I'd like to
tell new people to just default to pull --rebase, but having to add
(and explain) the "don't rebase a merge" caveat tends to lose them...
(yes we mix merge and rebase; it works for us... most of the time)

Thanks,
Stephen