Re: [PATCH] filter-branch: return 2 when nothing to rewrite

[Jeff King <peff@peff.net>]

On Thu, Mar 15, 2018 at 08:42:54AM -0700, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > On Thu, Mar 15, 2018 at 02:03:59PM +0100, Michele Locati wrote:
> >
> >> Using the --state-branch option allows us to perform incremental filtering.
> >> This may lead to having nothing to rewrite in subsequent filtering, so we need
> >> a way to recognize this case.
> >> So, let's exit with 2 instead of 1 when this "error" occurs.
> >
> > That sounds like a good feature. It doesn't look like we use "2" for
> > anything else currently.
> 
> I do not want to sound overly negative against the first
> contribution from a new contributor, but I am not sure if this is a
> good idea.  While I do agree that the caller of filter-branch would
> want _some_ way to tell if the call
> 
>  - got some new stuff,
>  - got no error but did not get anything new, or
>  - failed
> 
> and act accordingly, changing the exit code to a non-zero value for
> the second case above would mean that existing scripts that have
> happily been working would suddenly start failing.  Due to the lack
> of an easy way to tell the first two cases apart, they may have been
> doing _extra_ work after calling filter-branch when it found no new
> development (resulting in an expensive no-op), or perhaps they
> implemented their own way to tell the second case apart from the
> first one and efficiently omitting extra work in the second case
> already.  In either case, these scripts will get broken with this
> change.

Hrm. I took the goal to mean that we used to exit with a failing "1" in
this case, and now we would switch to a more-specific "2". And I think
that matches the behavior of the patch:

-test $commits -eq 0 && die "Found nothing to rewrite"
+test $commits -eq 0 && die_with_status 2 "Found nothing to rewrite"

Am I missing something?

-Peff