Re: git gc seems to break --symbolic-full-name

From: Jeff King <peff@peff.net>
Date: Jul 26, 2017, 13:23 UTC
Message-ID: <20170726132322.4cfj73tynrko264o@sigill.intra.peff.net>
In-Reply-To: <a6738cae-ad8d-cf51-0fbb-428cf0f88703@list.ru>

On Wed, Jul 26, 2017 at 11:40:46AM +0300, Stas Sergeev wrote:

Show 22 quoted lines

> 26.07.2017 03:36, Jacob Keller пишет:
> > If your goal is to make it so users filling out bug reports have a
> > version, then using git descrsibe and making that be part of your
> > version (based off your tags, and commits) is how pretty much every
> > other project I've worked on does this.
> > 
> > I really don't think that's your goal here, given you're doing things
> > in make with timestamps and builds, so I guess I misunderstood your
> > answer?
> There are 2 different things:
> 1. put git describe output into some header file
> 2. make things to rebuild with every new commit
> 
> So I actually stuck at solving 2, because 1 is trivial.
> My original solution for 2 was to "depend" on
> refs/heads/*. This worked besides git gc, but had
> a lot of troubles with worktrees. And this time I
> switched to the "touch tmpfile" trick with the date
> taken from git log. This requires .LOW_RESOLUTION_TIME
> in makefile, so probably not the best solution again,
> but should hopefully be more future-proof than the
> previous one.

In git.git we do something like:

-- >8 --
other: version
	cat $< >$@

.PHONY: FORCE
version: FORCE
	@git rev-parse HEAD >$@+
	@if cmp $@+ $@ >/dev/null 2>&1; then rm $@+; else mv $@+ $@; fi
-- >8 --

The "version" commands run always, but they only update the file if there's a change. At least GNU make is smart enough to know that if "version" was not updated, then "other" does not need to be re-built. I don't know if all makes would so, though.

-Peff