Re: [PATCH 0/2] Make diff plumbing commands respect the indentHeuristic.

From: Jeff King <peff@peff.net>
Date: May 9, 2017, 03:16 UTC
Message-ID: <20170509031653.7hc36pil3vzrobsz@sigill.intra.peff.net>
In-Reply-To: <CACBZZX5f81HKCjRjTDyXzNMVuef9Z_ECS+0SVk2xpbwXudgxCw@mail.gmail.com>

On Mon, May 01, 2017 at 12:34:38PM +0200, Ævar Arnfjörð Bjarmason wrote:

Show 14 quoted lines

> > I don't know if we would want to be extra paranoid about patch-ids.
> > There is no helping:
> >
> >   git rev-list HEAD | git diff-tree --stdin -p | git patch-id --stable
> >
> > because diff-tree doesn't know that it's trying for "--stable" output.
> > But the diffs we compute internally for patch-id could disable the
> > heuristics. I'm not sure if those matter, though. AFAIK those are used
> > only for internal comparisons within a single program. I.e., we never
> > compare them against input from the user, nor do we output them to the
> > user. So they'll change, but I don't think anybody would care.
> 
> I have a few-million row table with commit_id as one column & patch_id
> as another. I.e. a commit -> patch_id mapping.

Thanks for this data point. It's always interesting to hear about unforeseen uses of the tools.

Out of curiosity, how do you generate the patch-ids? Is it with something like diff-tree piped to patch-id?

I do feel a bit sad about breaking this case (or at the very least forcing you to set an option to retain cross-version compatibility). But my gut says that we don't want to lock ourselves into never changing the diff algorithm (and I'm sure we've done it inadvertently a few times over the years; even the recent switch to turning on renames would have had that impact).

-Peff