is-a-dev/.github/workflows/pr-branches.yml

name: PR Branches

on:
    workflow_dispatch:

jobs:
    update:
        name: Update
        runs-on: ubuntu-latest

        steps:
            - name: Update branches
              uses: actions/github-script@v8
              with:
                  github-token: ${{ secrets.BOT }}
                  script: |
                      const marker = "<!-- is-a-dev-bot: merge-conflict -->";

                      const prs = await github.paginate(
                          github.rest.pulls.list,
                          {
                              owner: context.repo.owner,
                              repo: context.repo.repo,
                              state: "open",
                              per_page: 100
                          }
                      );

                      console.log(`Found ${prs.length} open PRs`);

                      for (const pr of prs) {
                          try {
                              await github.rest.pulls.updateBranch({
                                  owner: context.repo.owner,
                                  repo: context.repo.repo,
                                  pull_number: pr.number
                              });

                              console.log(`Updated #${pr.number} (${pr.head.ref})`);
                          } catch (error) {
                              console.log(`Could not update #${pr.number}: ${error.message}`);

                              const { data: updatedPr } = await github.rest.pulls.get({
                                  owner: context.repo.owner,
                                  repo: context.repo.repo,
                                  pull_number: pr.number
                              });

                              if (updatedPr.mergeable !== false) {
                                  continue;
                              }

                              await github.rest.issues.addLabels({
                                  owner: context.repo.owner,
                                  repo: context.repo.repo,
                                  issue_number: pr.number,
                                  labels: ["reason: merge conflict"]
                              });

                              const comments = await github.paginate(
                                  github.rest.issues.listComments,
                                  {
                                      owner: context.repo.owner,
                                      repo: context.repo.repo,
                                      issue_number: pr.number
                                  }
                              );

                              const alreadyCommented = comments.some(
                                  (comment) =>
                                      comment.user?.login === "is-a-dev-bot" &&
                                      comment.body?.includes(marker)
                              );

                              if (!alreadyCommented) {
                                  const body = [
                                      marker,
                                      "## ❌ Merge conflict",
                                      "",
                                      "This pull request can not be merged because it has merge conflicts with `main`.",
                                      "",
                                      "***Please resolve the merge conflicts before this PR can be merged!***"
                                  ].join("\n");

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

                              console.log(`Marked #${pr.number} as having merge conflicts`);
                          }
                      }