ci: compliance: fetch only the last revision and skip tags

[fabiobaltieri]

Add some west update flags to do a shallow fetch of the modules and skip the tags. That data is not needed anyway, should make the compliance check initialization a bit faster.

---

Speeds up the "west setup" step from ~3:30m to ~1m40.

[marc-hb]

This would work only for PRs that have a single commit

./scripts/ci/check_compliance.py -h

options:
  -h, --help            show this help message and exit
  -c COMMITS, --commits COMMITS
                        Commit range in the form: a..[b], default is HEAD~1..HEAD

Try west update --fetch-opt=--filter=tree:0

We've been using that for a long time and it worked great in CI

• thesofproject/sof@6838224

• Consider adding config option for treeless clones (--fetch-opt=--filter=...) west#638

• Shallow cloning can create pull requests with one million commits thesofproject/linux#2556 (comment)

Just realized this is only for modules sorry

[fabiobaltieri]

@marc-hb thanks for the comment - yes it's only for the modules so it should work fine, I actualy never used the filter option, will look into that, thanks for the pointers. :-)

I did look into optimizing the main checkout as well but it's tricky to do a shallow fetch and not mess up the rebase step, maybe there's some clever filter that could be use to expand the history on top of a shallow fetch to just the right amount.

[marc-hb]

maybe there's some clever filter that could be use to expand the history on top of a shallow fetch to just the right amount.

It is when trying exactly that that I ended up with Pull Requests with a million commits, see picture in

• Shallow cloning can create pull requests with one million commits thesofproject/linux#2556 (comment)

Granted: this was in a repo with a lot of git merges and other git "backflips". It wouldn't happen with a linear history like Zephyr's.

I thought there would be a Github Action ready to "Just give me all the commits in the PR" but I later realized it is actually quite tricky in the general case.

https://github.com/thesofproject/sof/blob/main/.github/workflows/shallowfetchPRcommits.sh has been working fine for a long time but again this has been on a mostly linear git history. It's also an ugly shellscript, not a proper Github Action. Note a shell script is probably easier to test locally..

See also (too) long discussion in

• How do I fetch all commits only in the PR branch actions/checkout#552