Enforce "Squash and Merge" depending on PR label rather than specific branch. New feature request: Label protection rules

[ferdymercury]

🏷️ Discussion Type

Question

💬 Feature/Topic Area

Workflow Configuration

Discussion Details

In a PR, one could choose freely between "Merge" or "Squash and Merge".
I would like to use a GitHub action to disallow one of the two options depending on a specific label that I add to the PR.

This is different from configuring a specific branch to have only one of the two (https://github.com/orgs/community/discussions/10809). It's done dynamically depending on the PR of the contributor to which I would add a label "squash" or "not-squash", eg.

I see it's possible to fully block the merge using https://bgenc.net/2023.02.18.github-actions-do-not-merge-label/ but I don't know if it's doable to only block one of the two variants?

If that's impossible, is it doable to switch the default enabled button to one or the other depending on that label? I only found this very generic related answer: https://github.com/orgs/community/discussions/148702

If not, I'd would recommend this as a new feature for GitHub called "Label protection rules" on top of the "Branch protection rules"!

Thanks in advance for your advice.

[ideepakchauhan7]

Hey @ferdymercury! Unfortunately, GitHub doesn't currently offer a native way to restrict which merge button (Merge vs Squash and Merge) is available based on PR labels — the merge method enforcement in branch/repository rules applies globally to a branch, not conditionally per-label.

That said, here's a practical workaround using GitHub Actions that achieves the same goal: label-driven auto-merge via the API, so the merge method is enforced programmatically rather than through the UI.

Approach: Label-triggered auto-merge with the correct method

1. Disable all merge methods except one in repo settings (or use a ruleset to block direct UI merges) so contributors can't click the button themselves.
2. Use a workflow that watches for a specific label (e.g., automerge-squash or automerge-merge) and calls the GitHub API with the correct merge_method.

name: Label-driven merge

on:
  pull_request:
    types: [labeled]

jobs:
  merge:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
      contents: write
    steps:
      - name: Determine merge method from label
        id: method
        run: |
          LABELS='${{ toJson(github.event.pull_request.labels.*.name) }}'
          if echo "$LABELS" | grep -q '"automerge-squash"'; then
            echo "method=squash" >> $GITHUB_OUTPUT
          elif echo "$LABELS" | grep -q '"automerge-merge"'; then
            echo "method=merge" >> $GITHUB_OUTPUT
          else
            echo "method=none" >> $GITHUB_OUTPUT
          fi

      - name: Merge PR with correct method
        if: steps.method.outputs.method != 'none'
        uses: actions/github-script@v7
        with:
          script: |
            await github.rest.pulls.merge({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: context.payload.pull_request.number,
              merge_method: '${{ steps.method.outputs.method }}'
            });

If you only want to block a specific merge method (not auto-merge)

This is harder because GitHub Actions can't intercept a UI merge button click before it happens. The closest you can get is:

• Add a required status check that runs on every PR
• In that check, detect the label and set the check to failure with a message like "This PR is labeled 'squash-only' — please use Squash and Merge"
• This won't prevent the wrong button from being clicked, but it will block the merge from completing if the branch protection requires all checks to pass

Unfortunately that still doesn't technically restrict the UI button — it just blocks merging entirely, which isn't quite what you're after.

Feature request

Agreed this would be a great addition as "Label protection rules" — essentially making merge method a per-PR ruleset condition. You might want to upvote or reference the existing feature discussion at https://github.com/orgs/community/discussions/148702 to help get traction on it.

Hope that helps!

[ferdymercury]

Thanks for the suggestion about automerge labels, however that is suboptimal, since the advantage of the Squash and Merge button in the GUI is that the maintainer can customize the squashed message by hand.

[KunalSiyag]

Hi @ferdymercury! Currently, GitHub doesn't support dynamic UI changes (like hiding specific merge buttons) based on PR labels. Merge options are managed globally in the repo settings.

However, you can achieve the same enforcement by using a GitHub Action as a Required Status Check:

• The Workflow: Create an Action that triggers on pull_request labeled events.
• The Logic: Have the Action check the PR's labels. If the label doesn't match the intended merge style (or if a label is missing), the Action fails.
• The Protection: In your Branch Protection Rules, enable 'Require status checks to pass before merging'.

While this won't hide the button, it will stay grayed out and prevent anyone from merging until the conditions of your label-logic are met.

Hope this works.