Optimise fetching all commits in a pull request

[kellyselden]

My goal is to lint all commit messages in a pull request, or in other words, since branching off the default branch. My workaround is

    - uses: actions/checkout@v2
      with:
        fetch-depth: 0
        ref: ${{ github.event.pull_request.head.sha }}
    # grab default branch to calculate branch point to know when to stop linting
    - if: ${{ github.base_ref }}
      run: git branch ${{ github.base_ref }} origin/${{ github.base_ref }}

but for large repos, it would be nice if this action could do the smart thing and only fetch what is needed. Thanks in advance.

[ericzolf]

My use case is different but the need is the same: I want to be able to list all files changed in the PR (and decide accordingly if a step needs to be run) but it can only work if the base_ref is also fetched, which currently, not knowing the number of commits required, can only be done by fetching the whole repository.

[ericsciple]

if the base_ref is also fetched

An easy workaround given the existing behavior may be to add an additional checkout step (first) that checks out the base ref. That way all the files get fetched, and you can do the diff after the second checkout step.

I say "easy" because it's easier than scripting the fetch command yourself and formulating the correct refspec and other options :)

[so0k]

what does the correct refspec look like, what's the difference with running

git branch ${{ github.base_ref }} origin/${{ github.base_ref }}

I don't see anything in the pull_request body that tells me how many commits to fetch if you do a shallow clone

the alternative seems to be

https://stackoverflow.com/a/56113247

while [ -z $( git merge-base  ${{ github.base_ref }}  ${{ github.head_ref }}) ]; do
    git fetch -q --deepen=10 origin ${{ github.base_ref }}  ${{ github.head_ref }};
done

EDIT: the --deepen gave me an infinite loop

[aaglietti-itsrizzoli]

@kellyselden I run in a similar issue and I've manage to avoid using the full fetch-depth, take a look here https://github.com/ITSRizzoli/2021-23.SA.UFS07/blob/00e213128951cbc05c2ef7ba186923da10417653/.github/workflows/scripts/pr-requirements/pr-incoming-convetional-commits-lint.sh#L26

[polarathene]

I don't see anything in the pull_request body that tells me how many commits to fetch if you do a shallow clone

${{ github.event.pull_request.commits }} is available for that. I guess it was not a year ago.