Bug#930487: lintian: use GitLab caching of test packages to speed up test suite CI

["Chris Lamb" <lamby@debian.org>]

Felix Lechner wrote:

> > I've been hacking on this on a Salsa-local fork of Lintian that splits
> > the generation of the test packages and the testing itself, crucially
> > caching the result of the former if the tests and some other key files
> > have not changed.
> 
> How do you tell when files have changed? I would like to use an MD5
> manifest of all files generated after templating.

Computing the checksum of the output not only seems unnecessarily
complicated but prone to error in the details. I am hashing the entire
"input" roughly as follows:

 $ find t/ debian/ -type f | sort | xargs sha1sum | sha1sum | cut -d' ' -f1
 
.. throwing the entire set of build packages away in the case of cache
miss.

Of course there are more refined approaches but, in lieu of that, if
you skim over the pipeline job history this will save the testsuite
package builds almost all of the time. This also has the advantage of
being obvious how it works and captures any type of change, including
the missing files that you specifically highlight, but possibly even
others we have not yet thought of.

I am very much disposed towards simple and braindead obvious in things
like this, especially when they hit 90% of the use-case. And then we
can get back to other stuff...

Anyway, without the Salsa caching working, all of this is moot.


Regards,

-- 
      ,''`.
     : :'  :     Chris Lamb
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