kousu / cache Goto Github PK

TravisCI is limited in what folders it will cache, but it is smart about detecting when they have been updated: https://docs.travis-ci.com/user/caching/.

In contrast, GithubCI's caching mechanism expects that you can pre-compute, from only the contents of your repo, a cache key to identify your cache. Caches are write-once in Github. The closest thing to updating a cache is by using restore-keys eg.

    - name: Download annex cache
      id: cache
      uses: actions/cache@v2
      with:
        path: |
          ~/.annex-cache
        key: annex-${{ hashFiles('**/*.nii.gz, **/*.nii') }}
        restore-keys: |
          annex-

In this, annex- is a prefix of every cache, so if the exact cache doesn't exist yet, the most recently generated cache will be downloaded instead.

This is inconvenient, and can even fail if:

• you haven't precisely pinned your dependencies and they update under you
• some other content in your cache shifts

I don't want to have to think about all that.

The idea of this fork is to behave more like Travis: download the most recent cache, but then upload. So far, it needs to be used like this:

    - name: caching
      uses: kousu/cache@main
      with:
        path: .cache
        key: mycache-${{ hashFiles('.cache') }}
        restore-keys: |
          mycache-

because I haven't found where or if hashFiles() is available in the Github javascript libraries, it needs to be fed in from the Workflow language. You need to make sure the path used in hashFiles() matches the path used in path: and that the restore-keys: prefix matches the prefix used in key:. Another caveat is that hashFiles is strictly limited, I guess as an anti-abuse measure, to reading files within your repo, so you'll need to, I dunno, rsync or symlink or something to cache things in e.g. ~/.npm or ~/.cache/pip.