From: Jeff King <peff@peff.net>
Date: Fri, 16 Jan 2026 16:54:51 GMT
Subject: Re: [PATCH 0/2] more t/perf meson/GIT-BUILD-OPTIONS fallout
Message-ID: <20260116165451.GB1636797@coredump.intra.peff.net>
In-Reply-To: <1a430542-715e-4cf1-86f5-d9424951204a@ramsayjones.plus.com>

On Tue, Jan 06, 2026 at 05:07:11PM +0000, Ramsay Jones wrote:

> I hesitated to send this email because I have been reduced to simply skimming
> the git mailing list (very busy with other projects/real life!), and I may
> have misunderstood what you aim to do here. ;)
> 
> In essence, I was triggered by the 'GIT-BUILD-OPTIONS fallout' phrase in the
> subject line! That reminded me of a problem/patch I was looking at earlier
> this (wait, last) year. The patch (below) was a complete 'hack' (as you can
> see) to allow the environment to override the 'GIT-BUILD-OPTIONS' file. This
> was in an old branch named 'meson-wip' which I have been meaning to look at
> again to either delete or fix-up.
> 
> One of the many reasons (apart from being a disgusting hack) that I didn't
> progress this patch is because I felt that not all 'options' in that file
> should be able to be 'overridden'. So, that implies that the file needs to
> be split into two; one file of options which can be overridden from the
> environment and one that can't. If so, then someone has to decide which is
> which.

I think you understood my goal. :) This is more or less what my patch is
doing, but just for a select set of options (to un-break t/perf). I
think a larger fix may look something like this, but:

  1. I agree with you that we may need to consider which options should
     be able to be overridden and which should not.

  2. This hack has to go everywhere that GIT-BUILD-OPTIONS is read. So
     in test-lib.sh where you have it, but also in perf-lib.sh (matching
     the fix by Dscho earlier) and also in t/perf/run (matching the fix
     here).

It would be nice if we could write GIT-BUILD-OPTIONS in a way that did
the right thing. E.g., by writing:

  : ${GIT_FOO:=some-value}

And then the writer (which is the ultimate source of authority for which
variables are included) could decide which ones can be overridden.

I _thought_ this wouldn't work because we also source the build options
files from the Makefile (and so it has to support both syntaxes). But a
quick grep doesn't show us including it. So maybe we used to do so, or
maybe I'm mis-remembering (and confusing it with GIT-VERSION-FILE
perhaps?).

-Peff