Use caching in the github actions

[bschmalhofer]

Here is another idea. When looking at https://github.com/RotherOSS/otobo/runs/3684898399?check_suite_focus=true we see that there is one step that takes most of the time. That's installing the CPAN dependencies from cpanfile.docker. This could be eliminated by using a dedicated Docker image with all the dependencies installed. A better idea might be to simply cache the CPAN dependencies. Either the directory with the installed Perl modules, or the .cpanm workdir.

Originally posted by @bschmalhofer in https://github.com/RotherOSS/CodePolicy/issues/51#issuecomment-925749171

[bschmalhofer]

It is not clear whether this works as expected. There are several cases to be checked:

• action on push: cache is used when pushing to the same branch
• action on pull_request: cache is used when rerunning the job
• action on pull_request, no cache in parent branch: cache is not used on the next PR
• action on pull_request, with cache in parent branch: cache is used on the next PR

[bschmalhofer]

Another optimisation in cache_local_lib.yml. For getting a checksum on cpanfile.docker, we don't need a complete checkout of the branch. We can ask Github directly via the REST interface. Unfortunately the SHA from the webservice is not the same value as returned by hashfiles(). This can be redeemed by using git rev-parse :cpanfile.docker in the other workflows.

Still not closing, in case problems crop up.

[bschmalhofer]

After discussion with @svenoe and consulting #1110 we deciding to merge the two check actions.

[bschmalhofer]

Looks good. Only the code_policy.yml workflow is now executed. This workflow contains the syntax check.

[bschmalhofer]

This seems to work without hassle. Let's use it for rel-10_0 as well.

[bschmalhofer]

Another idea for a speedup. Install Code::TidyAll and dependencies via cpanm. This should make the installation of Debian packages faster.

[bschmalhofer]

Closing this issue. Any problems that pop up should be fixed in #1278.