Re: [PATCH 3/4] Makefile: use the sha1collisiondetection submodule by default

[Kevin Daudt <me@ikke.info>]

On Tue, Dec 05, 2017 at 02:02:50AM -0500, Jeff King wrote:
> On Tue, Nov 28, 2017 at 09:32:13PM +0000, Ævar Arnfjörð Bjarmason wrote:
> 
> > Change the build process so that instead of needing to supply
> > DC_SHA1_SUBMODULE=YesPlease to use the sha1collisiondetection
> > submodule instead of the copy of the same code shipped in the sha1dc
> > directory, it uses the submodule by default unless
> > NO_DC_SHA1_SUBMODULE=UnfortunatelyYes is supplied.
> > 
> > This reverses the logic added by me in 86cfd61e6b ("sha1dc: optionally
> > use sha1collisiondetection as a submodule", 2017-07-01). Git has now
> > shipped with the submodule in git.git for two major releases, if we're
> > ever going to migrate to fully using it instead of perpetually
> > maintaining both sha1collisiondetection and the sha1dc directory this
> > is a logical first step.
> > 
> > This change removes the "auto" logic Junio added in
> > cac87dc01d ("sha1collisiondetection: automatically enable when
> > submodule is populated", 2017-07-01), I feel that automatically
> > falling back to using sha1dc would defeat the point, which is to smoke
> > out any remaining users of git.git who have issues cloning the
> > submodule for whatever reason.
> 
> I'm not sure how I feel about this. I see your point that there's no
> real value in maintaining two systems indefinitely.  At the same time, I
> wonder how much value the submodule strategy is actually bringing us.
> 
> IOW, are we agreed that the path forward is to get everybody using the
> submodule?
> 
> It seems like it's going to cause some minor pain for CI and packaging
> systems that now need to care about submodules (so at least flipping the
> switch, but maybe also dealing with having a network dependency for the
> build that was not already there).
> 
> I'll admit I'm more sensitive to this than most people, since I happen
> to maintain a fork of Git that I run through an internal CI system. And
> that CI otherwise depends only on the locally-held fork, not any
> external resources. But I'm probably in a fairly unique situation there.
> 
> -Peff

To add to this point, package systems such as Alpinelinux and Archlinux
(and probably others) work with released tarballs, not cloned
repositories. For them, there is no easy way to get the submodule
contents (the release tarballs would not contain it).

Once we would switch over to submodules only (because we do not want to
maintain 2 separate systems), it would be a lot of hassle for those
projects to get the sha1collisiondetection contents.

That's in my opinion a bigger disadvantage of submodules, commands like
git archive do not support it, making it harder to get self-contained
tarballs.

Perpahs there is a good solution to that problem, but then I'd like to
hear it.

Kevin.