get_changed_env.yml

name: Get changed conda envs
on:
  workflow_call:
    outputs:
      matrix: 
        value: ${{ jobs.generate_matrix.outputs.matrix }}
jobs:
  generate_matrix:
    name: Determine changed environments
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.diff.outputs.matrix }}
    steps:
      - uses: actions/checkout@v4
      - name: Check changed environments
        id: diff
        run: |
          # See https://github.community/t/check-pushed-file-changes-with-git-diff-tree-in-github-actions/17220/10
          ### https://stackoverflow.com/questions/59977364/github-actions-how-use-strategy-matrix-with-script
          if [ $GITHUB_BASE_REF ]; then
            # Pull Request
            git fetch origin $GITHUB_BASE_REF --depth=1
            export DIFF=$( git diff --name-only origin/$GITHUB_BASE_REF $GITHUB_SHA )
            echo "Diff between origin/$GITHUB_BASE_REF and $GITHUB_SHA"
          else
            # Push
            git fetch origin ${{ github.event.before }} --depth=1
            export DIFF=$( git diff --name-only ${{ github.event.before }} $GITHUB_SHA )
            echo "Diff between ${{ github.event.before }} and $GITHUB_SHA"
          fi
          json="{\"include\":["
          for line in $DIFF; do
            if [[ $line =~ environments ]]; then
                env_name=$( basename ${line%/*} )
                if ! [[ $json =~ $env_name ]]; then
                    json="$json{\"environment\":\"$env_name\"},"
                fi
            fi
          done
          ### https://github.com/actions/runner/issues/2947
          echo "matrix=$( echo "${json%,}]}" | jq -r 'tostring' )" >> $GITHUB_OUTPUT