action.yml

name: Check branch behind
description: |
  Checks if the current revision is at head of the default branch.

  Use this step if you want to be sure that you run CI job using the HEAD of the branch. Local branch in CI runner might be not up to date with remote because CI jobs are usually triggered on commit push and checkout this commit.

  As a result this step can exit with `1` status code or set output depending on `exit_on_fail` parameter.
inputs:
  is_base_ref:
    description: 'If true, performs the check using the current commit as base ref'
    required: false
    default: "false"
  exit_on_fail:
    description: 'If true, throws on error'
    required: false
    default: "false"
  remote_update:
    description: 'Use git remote update instead of fetch'
    required: false
    default: "false"
  git_default_branch:
    description: 'Default git branch'
    required: false
    default: "master"
outputs:
  branch_up_to_date:
    description: "true if the branch is up to date"
    value: ${{ steps.check_branch_behind.outputs.branch_up_to_date }}
runs:
  using: "composite"
  steps:
    - name: Check if at head of branch
      id: check_branch_behind
      shell: bash
      run: |
        if [[ "${{ inputs.is_base_ref }}" == "true" ]]; then
          if [[ "${{ inputs.remote_update }}" == "true" ]]; then
            git remote update
          else
            git fetch --depth=1 origin "${{ inputs.git_default_branch }}"
          fi
          
          local=${{ github.sha }}
          remote=$(git rev-parse origin/"${{ inputs.git_default_branch }}")
        else
          git fetch --depth=1 origin "${{ github.head_ref }}"
          local=${{ github.event.pull_request.head.sha }}
          remote=$(git rev-parse "origin/${{ github.head_ref }}")
        fi
        
        echo "$remote"
        if [ "$local" == "$remote" ]; then
          echo "Looks like we're at the head of the branch."
          echo "branch_up_to_date=true" >> "$GITHUB_OUTPUT"
        else
          echo "Local branch is not up to date with remote. Exiting."
        
          if [[ "${{ inputs.exit_on_fail }}" == "true" ]]; then
            exit 1
          fi
         
          echo "branch_up_to_date=false" >> "$GITHUB_OUTPUT"
        fi