.github/workflows/post-merge.yml

# Workflow that runs after a merge to the default branch, analyses changes in test executions
# and posts the result to the merged PR.

name: Post merge analysis

on:
  push:
    branches:
      - main

jobs:
  analysis:
    runs-on: ubuntu-24.04
    if: github.repository == 'rust-lang/rust'
    permissions:
      pull-requests: write
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          # Make sure that we have enough commits to find the parent merge commit.
          # Since all merges should be through merge commits, fetching two commits
          # should be enough to get the parent bors merge commit.
          fetch-depth: 2
      - name: Perform analysis and send PR
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          # Give GitHub some time to propagate the information that the PR was merged
          sleep 60

          # Get closest bors merge commit
          PARENT_COMMIT=`git rev-list --author='bors@rust-lang.org' --author='122020455+rust-bors\[bot\]@users.noreply.github.com' -n1 --first-parent HEAD^1`
          echo "Parent: ${PARENT_COMMIT}"

          # Find PR for the current commit
          HEAD_PR=`gh pr list --search "${{ github.sha }}" --state merged --json number --jq '.[0].number'`
          if [ -z "${HEAD_PR}" ]; then
            echo "PR for commit SHA ${{ github.sha }} not found, exiting"
            exit 1
          fi
          echo "HEAD: ${{ github.sha }} (#${HEAD_PR})"

          cd src/ci/citool

          printf "<details>\n<summary>What is this?</summary>\n" >> output.log
          printf "This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.\n" >> output.log
          printf "</details>\n\n" >> output.log

          cargo run --release post-merge-report ${PARENT_COMMIT} ${{ github.sha }} >> output.log

          cat output.log

          gh pr comment ${HEAD_PR} -F output.log