Super slow on large private repo

[peterbe]

Please describe your suggestion: 提案の概要

I'm adding this:

      - name: Gather diff files
        uses: technote-space/get-diff-action@947c47d16bc66137e567e55d74cdf752fed2695c
        id: get_diff_files
        with:
          SET_ENV_NAME: DIFF_FILES

It works. But it's really really slow. It takes about 3 minutes to complete.
Yes, the repo has a lot of files. Just doing the actions/checkout takes 10-11 seconds. So I don't understand why it should take 3 minutes to execute the git diff. Is it because the action depends on doing a non-shallow checkout or something?

Describe the solution you'd like: 考えうる解決方法

That it doesn't take so long.

Describe alternatives you've considered: 考えうる代替案

None.

Additional context: 補足

I might be able to set up a reproducible case on a "mirror" of this repo.