checkout@v2 doesn't allow `git diff origin/master`

[wdanilo]

Hi, I have such a step in my actions config:

    name: Get list of changed files
    id: changed_files
    run: |
        list=`git diff --name-only origin/master HEAD`
        echo $list
        echo "::set-output name=list::$list"
    shell: bash

When using checkout@v1 it works, while with checkout@v2 I get

fatal: ambiguous argument 'origin/master': unknown revision or path not in the working tree.

[skovhus]

If you want to git diff to work, then you need to fetch more than 1 commit (which is the default) for checkout@v2. By setting the fetch-depth to 0, you will fetch the entire git history:

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

See more: https://github.com/actions/checkout#checkout-head

[ljharb]

@skovhus wouldn't a better default for a PR be to fetch whatever commits are needed to include the PR base?

[skovhus]

@skovhus wouldn't a better default for a PR be to fetch whatever commits are needed to include the PR base?

If possible yes. Please share if you know how to do that with actions/checkout@v2.

[ljharb]

ah sorry, i assumed you were a maintainer.

I don't think it's something we can configure; i think it's something that the checkout action would have to do, by first making a call to the github API, to figure out the requisite fetch depth.

[Vasfed]

In PRs usually required depth is fetch-depth: ${{ github.event.pull_request.commits + 1}}
but math is not supported inside ${{}}

[kolyshkin]

I found out that that if you want something like git diff origin/master, you can do so with

- uses: actions/checkout@v3
   with:
    fetch-depth: 2
  - run: git diff HEAD~1

This works because the last commit being fetched is the merge commit (somehow created by github) which shows the full diff for the PR.

[JohnStarich]

This worked for me:

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v3
    - name: checkout
      run: |
        commits=${{ github.event.pull_request.commits }}
        if [[ -n "$commits" ]]; then
          # Prepare enough depth for diffs with master
          git fetch --depth="$(( commits + 1 ))"
        fi

For some actions, the diff is a rich source for data analyses. While this works, I'd love a built-in option (or default) to fetch the current PR's history.

[AllanOricil]

I also had to use origin/main instead of main for my diffs.

this does not work, even fetching all branches (fetch-depth: 0)

git diff ${{ github.base_ref }}..${{ github.sha }} 

this works

git diff origin/${{ github.base_ref }}..${{ github.sha }}