alternate-workflow.yml

name: Autoupdate PR branches from fork

on:
  issue_comment: 
    types: [created]

jobs:
  autoupdate-pr:
    if: >
      github.event_name == 'issue_comment' && (
        contains(github.event.comment.body, '/update') ||
        contains(github.event.comment.body, '/u')
      )
    runs-on: ubuntu-latest
    steps:
      - name: Get Pull Request Details
        id: pr
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.BOT_TOKEN || secrets.GITHUB_TOKEN }}
          previews: 'merge-info-preview' # https://docs.github.com/en/graphql/overview/schema-previews#merge-info-preview-more-detailed-information-about-a-pull-requests-merge-state-preview
          script: |
            const prNumber = context.payload.issue.number;
            core.debug(`PR Number: ${prNumber}`);
            const { data: pr } = await github.rest.pulls.get({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: prNumber
            });

            // If the PR has conflicts, we don't want to update it
            const updateable = ['behind', 'blocked', 'unknown', 'draft', 'clean'].includes(pr.mergeable_state);
            console.log(`PR #${prNumber} is ${pr.mergeable_state} and is ${updateable ? 'updateable' : 'not updateable'}`);
            core.setOutput('updateable', updateable);

            core.debug(`Updating PR #${prNumber} with head ${pr.head.sha}`);

            return {
              id: pr.node_id,
              number: prNumber,
              head: pr.head.sha,
            }
      - name: Update the Pull Request
        if: steps.pr.outputs.updateable == 'true'
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.BOT_TOKEN }}
          script: |
            const mutation = `mutation update($input: UpdatePullRequestBranchInput!) {
              updatePullRequestBranch(input: $input) {
                pullRequest {
                  mergeable
                }
              }
            }`;

            const pr_details = ${{ steps.pr.outputs.result }};

            try {
              const { data } = await github.graphql(mutation, {
                input: {
                  pullRequestId: pr_details.id,
                  expectedHeadOid: pr_details.head,
                }
              });
            } catch (GraphQLError) {
              core.debug(GraphQLError);
              if (
                GraphQLError.name === 'GraphqlResponseError' &&
                GraphQLError.errors.some(
                  error => error.type === 'FORBIDDEN' || error.type === 'UNAUTHORIZED'
                )
              ) {
                // Add comment to PR if the bot doesn't have permissions to update the PR

                const comment = `@${context.actor} I don't have permissions to update this PR. Please ask the PR author to check the "Allow edits from maintainers" checkbox in the PR settings.`;

                await github.rest.issues.createComment({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  issue_number: context.issue.number,
                  body: comment
                });

                core.setFailed('Bot does not have permissions to update the PR');
              } else {
                core.setFailed(GraphQLError.message);
              }
            }