Error: fatal: bad object ac7ed0108181239e44712926a3582ca96902bc68

[securestep9]

trying to run this action on a PR produces an error:
++ grep '.py$'
fatal: bad object ac7ed0108181239e44712926a3582ca96902bc68

[Athanasius]

Are you using checkout@v2 as first step? It defaults to git fetch ... --depth=1 which caused just such an issue for me. Easily work-around though:

    steps:
    - uses: actions/checkout@v2
      with:
        fetch-depth: 0

That makes it not do that, but fetch the entire history instead.