Re: [PATCH 0/2] Reinstate the helpful message when `git pull --rebase` fails

[Paul Tan <pyokagan@gmail.com>]

On Fri, Oct 9, 2015 at 8:52 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Johannes Schindelin <johannes.schindelin@gmx.de> writes:
>
>> Brendan Forster noticed that we no longer see the helpful message after
>> a failed `git pull --rebase`. It turns out that the builtin `am` calls
>> the recursive merge function directly, not via a separate process.
>>
>> But that function was not really safe to be called that way, as it
>> die()s pretty liberally.

I'm not too familiar with the merge-recursive.c code, but I was under
the impression that it only called die() under fatal conditions. In
common use cases, such as merge conflicts, it just errors out and the
helpful error message does get printed. Is there a reproduction recipe
for this?

That said, I do agree that even if we die(), we could try to be more
helpful by printing additional helpful instructions.

> If that is the case, I'd thinkg that we'd prefer, as a regression
> fix to correct "that", i.e., let recursive-merge die and let the
> caller catch its exit status.

We could do that, but I don't think it would be worth the overhead to
spawn an additional process for every patch just to print an
additional message should merge_recursive() call die().

Instead, stepping back a bit, I wonder if we can extend coverage of
the helpful message to all die() calls when running git-am. We could
just install a die routine with set_die_routine() in builtin/am.c.
Then, should die() be called anywhere, the helpful error message will
be printed as well. fast-import.c and http-backend.c seem to do this.

Regards,
Paul