[bug#50359] [PATCH 3/3] import: Add 'generic-git' updater.

[Xinglu Chen]

On Wed, Sep 15 2021, iskarian@mgsn.dev wrote:

> Hi,
>
> September 10, 2021 9:21 AM, "Xinglu Chen" <public@yoctocell.xyz> wrote:
>
>> * guix/git.scm (ls-remote-refs): New procedure.
>> * tests/git.scm ("remote-refs" "remote-refs: only tags"): New tests.
>> * guix/import/git.scm: New file.
>> * doc/guix.texi (Invoking guix refresh): Document it.
>> * tests/import-git.scm: New test file.
>> * Makefile.am (MODULES, SCM_TESTS): Register the new files.
>> 
>> Co-authored-by: Sarah Morgensen <iskarian@mgsn.dev>
>
> Overall this is looking good.  Thank you for adding tests (for
> remote-refs as well!), much appreciated.  It looks like you've done
> some good polishing.  I see a few nits, which I'll point out in a
> separate email when I'm not on mobile.  I'll also give it a good test.
>
> But... I've been thinking about the overall approach for a couple
> days, because I'm not very happy with the complexity of my heuristic.
>
> There can be a lot of weird tags in a repository--look at the one for
> xf86-video-intel for example.  My heuristic attempts to capture the
> assumption that repostories tend to move from using "_" or "-" to "."
> but it does fail to account for moving to or from dates (because dates
> don't compare with normal versions).

But if a repo moved from using versions to tags, or vice-versa, we still
wouldn’t know if say “3.0.1” is newer than “2021.03.02”.  We would have
to know when the “3.0.1” tag was created.

Maybe we could have a ‘release-tag-date-scheme?’ property, that way we
could just try to match dates?

> I also realized that we are not using a very useful piece of
> information--the previous version/tag combo.  I expect that in the
> vast majority of cases, the version delimiter for the newest version
> will be the same as the version delimiter for the last known version.
> (Perhaps the prefix as well?)  Can we use this information to make our
> guesses better?  What do you think?

That sounds like a good idea.  What should happen if the delimiter from
the previous version/tag combo is different from the one that the
‘guess-delimiter’ procedure returns?  Should the one from the previous
version/tag combo take precedence.

> Despite saying all that, it's probably better to not try to get it
> perfect on the first go--we can always adjust the internals later.  We
> just want to avoid showing bogus updates.

Yeah, we can always improve things later.
  
> (Later, I think I'll put together a dataset of tags and current
> versions to see if I can test how well a particular algorithm works.)

Cool, looking forward to that.  :-)

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