Auto add the target branch as a label to the PR

auto-labeling-with-target-branch.yml

name: PR Branch Labeler

on:
  pull_request:
    types: [opened, synchronize, reopened]

jobs:
  label-branch:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write

    steps:
      - name: Add branch label
        uses: actions/github-script@v7
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const targetBranch = context.payload.pull_request.base.ref;
            const labelName = `branch:${targetBranch}`;
            
            const labels = await github.rest.issues.listLabelsOnIssue({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.payload.pull_request.number
            });
            
            for (const label of labels.data) {
              if (label.name.startsWith('branch:')) {
                await github.rest.issues.removeLabel({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  issue_number: context.payload.pull_request.number,
                  name: label.name
                });
              }
            }
            
            await github.rest.issues.addLabels({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.payload.pull_request.number,
              labels: [labelName]
            });