How I keep open PRs in sync with main branch

• Github actions
• Ci cd
• Automation
• Workflow

I checked out Elastic’s docs-content repo, specifically its stale-sweep workflow: it flags documentation pages nobody has touched in a while and files issues to get them fixed. That reminded me of a related problem: open pull requests (PRs) drifting out of date. This post walks through a GitHub Actions workflow that keeps every open PR branch current with main automatically, so continuous integration (CI) always tests against it.

Why open PR branches fall behind

If you work in a docs-as-code workflow while managing multiple products, you’ve probably had several PRs open at once. You keep opening newer ones and merging them while the earlier ones wait on:

• a review that hasn’t happened yet
• a release that hasn’t shipped yet
• a change that needs a stakeholder’s sign-off
• an engineer who still needs to verify a technical detail

That’s all normal, and none of it means the PRs are wrong. But every merge to main leaves the waiting PRs a little further behind, and nothing flags it. A branch that’s fallen behind still passes every check, because those checks ran against an old main, not the current one.

Mine just needed to stay in sync with main while I moved on to the next thing. That’s the part I automated.

The fix

I set up a workflow built on the pull-request-updater action. In plain terms: whenever new commits land on main, it finds every open PR whose branch has fallen behind and merges them in automatically, skipping the ones already current. It doesn’t build, test, or deploy anything. It’s branch hygiene that runs alongside your CI checks.

Here’s the workflow file I’m running:

name: Auto-update PR branches
on:
  push:
    branches: [main] # run after every merge to main

jobs:
  autoupdate:
    runs-on: ubuntu-latest
    permissions:
      contents: write # update the PR branch
      pull-requests: write # act on open PRs
      issues: write # comment on each PR it updates (GitHub treats PR comments as issue comments)
    steps:
      - uses: wechuli/pull-request-updater@v2
        with:
          base: main # only update PRs that target main
          token: ${{ secrets.GITHUB_TOKEN }}

The base: main line scopes it to PRs that target main. Leave it out and the action updates every open PR, whatever branch it’s based on.

The challenge this doesn’t solve

Even with branches kept current, one thing still needs you: merge conflicts. When a PR’s changes collide with what’s already on main, GitHub marks it as conflicted, and you have to resolve it yourself before it can merge.

The pull-request-updater action is a small addition, but it keeps every open PR branch current with main on its own.

Have you run into PRs piling up in your own documentation workflow? I’d like to hear what you’ve tried.