caching pip and git-lfs in CI

[ismael-mendoza]

It might be nice to cache pip installation in the CI with like:

    - name: Cache pip
      uses: actions/cache@v2
      with:
        # This path is specific to Ubuntu
        path: ~/.cache/pip
        # Look to see if there is a cache hit for the corresponding requirements file
        key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
        restore-keys: |
          ${{ runner.os }}-pip-
          ${{ runner.os }}-

but I got inconsistent runs (sometimes taking longer than just installing) so more investigation is needed. It also caused an error for me in at least one test run

Also caching git-lfs might give us even more speed up: actions/checkout#165
but havent' tried it out yet.

[jeff-regier]

git-lfs appears to only take a few seconds to run, so there's probably not much benefit to caching that data it pulls.

I wonder how much time we'd save by caching the dependencies pip installs.

[ismael-mendoza]

hmm good point, I tried caching pip once and it didn't really help much. I just assumed that I was doing it wrong but perhaps I wasn't. I'll close this for now, it consistently takes 2 min to pip install all dependencies which is not terrible.