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

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

Hi all,

> lintian: use GitLab caching of test packages to speed up test suite CI

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.

I have something working except that I am running into a blocker
whereby the GitLab cache is not seen in subsequent runs.

For example, the cache is being stored at the end of the test package
build stage:

    Creating cache default-2...
    .cache/: found 2 matching files                    
    No URL provided, cache will be not uploaded to shared cache server. Cache will be stored only locally. 
    Created cache

… but it is not seen when you re-run that same pipeline:

    Checking cache for default-2...
    No URL provided, cache will not be downloaded from shared cache server. Instead a local version of cache will be extracted. 
    Successfully extracted cache
    
    $ ls -l .cache || true
    ls: cannot access '.cache': No such file or directory

I will try and hunt down a Salsa admin during DebConf. This might be
due to the use of shared runners and us not using a centralised cache.


Regards,

-- 
      ,''`.
     : :'  :     Chris Lamb
     `. `'`      lamby@debian.org / chris-lamb.co.uk
       `-