Re: [PATCH 2/2] xdiff: implement empty line chunk heuristic

From: Jeff King <peff@peff.net>
Date: Apr 30, 2016, 03:06 UTC
Message-ID: <20160430030620.GB25719@sigill.intra.peff.net>
In-Reply-To: <CAGZ79kZu=keNaCbt4T=CzH3i9qr+BxXw6AiWR-q1Cs4U80Jzng@mail.gmail.com>

On Fri, Apr 29, 2016 at 03:35:54PM -0700, Stefan Beller wrote:

Show 14 quoted lines

> > -- >8 --
> > diff: enable "compaction heuristics" and lose experimentation knob
> >
> > It seems that the new "find a good hunk boundary by locating a blank
> > line" heuristics gives much more pleasant result without much
> > noticeable downsides.  Let's make it the new algorithm for real,
> > without the opt-out knob we added while experimenting with it.
> 
> I would remove the opt-out knob much later in the game, i.e.
> 
>     1) make a patch that removes the documentation only
>        before the next release (i.e. before 2.9)
>     2) make a patch to remove the actual (unlabeled) knobs,
>         merge into master before 2.10 (i.e. just after the 2.9 release)

Yeah, I think it might be a good idea to keep some sort of undocumented safety valve in the release, at least for a cycle or two. The heuristic won't _really_ see wide use until it is in a released version of git, as much as we would like it to be otherwise.

So I am anticipating a possible conversation where somebody reports that the new output looks bad, and it would be nice to say "try it with this flag (or environment variable, or whatever) and see if that looks better". And then based on that conversation we can decide what the right next is (a real user-visible flag, or reversion, or deciding the user's case isn't worth it). Or maybe if we're lucky that conversation never happens.

The "whatever" in the instructions can obviously be "build with this patch" or "try with an older version of git", but we're a lot more likely to get a good response if it's easy for the user to do.

-Peff