action.yml

name: Commit changes
description: >-
  Commits what changed under the given paths (screenshots, baselines, generated files) as
  github-actions[bot] and pushes it to the branch the workflow runs on. Nothing changed: nothing
  is committed. The job needs contents: write; a push with the GITHUB_TOKEN starts no other workflow.
  It pushes with whatever actions/checkout set up, e.g. its ssh-key for a deploy key.

inputs:
  paths:
    description: What is committed, one path or glob per line
    required: true
  message:
    description: Commit message
    default: Update screenshots

outputs:
  changed:
    description: "true when something was committed"
    value: ${{ steps.commit.outputs.changed }}

runs:
  using: composite
  steps:
    - id: commit
      shell: bash
      env:
        PATHS: ${{ inputs.paths }}
        MESSAGE: ${{ inputs.message }}
      run: |
        set -euo pipefail
        if [[ "$GITHUB_REF" != refs/heads/* ]]; then
          echo "::error::Run this on a branch, not on $GITHUB_REF"
          exit 1
        fi
        # In a container the workspace belongs to another user
        git config --global --add safe.directory "$GITHUB_WORKSPACE"
        git config user.name "github-actions[bot]"
        git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
        mapfile -t pathspecs < <(printf '%s\n' "$PATHS" | sed '/^[[:space:]]*$/d')
        git add -- "${pathspecs[@]}"
        if git diff --cached --quiet; then
          echo "Nothing changed." | tee -a "$GITHUB_STEP_SUMMARY"
          echo "changed=false" >> "$GITHUB_OUTPUT"
          exit 0
        fi
        { echo "Committed:"; git diff --cached --name-only | sed 's/^/- /'; } >> "$GITHUB_STEP_SUMMARY"
        git commit -m "$MESSAGE"
        # The branch may have moved during the run (a push, another run): put the commit on top
        # of it and try again; a conflict in the same files stops here
        branch="${GITHUB_REF#refs/heads/}"
        for attempt in 1 2 3 4 5; do
          git push origin "HEAD:$GITHUB_REF" && break
          if (( attempt == 5 )); then
            echo "::error::Could not push to $branch"
            exit 1
          fi
          sleep $((attempt * 2))
          git fetch origin "$branch"
          git rebase "origin/$branch"
        done
        echo "changed=true" >> "$GITHUB_OUTPUT"