Push i18n POT file to a separate branch

Author: webknjaz

.github/workflows/translation.yml

@@ -9,19 +9,46 @@ on:
      types:
      - completed
 
+env:
+  I18N_BRANCH: translation/source
+
 jobs:
    build:
      runs-on: ubuntu-latest
 
      steps:
        - name: Grab the repo src
          uses: actions/checkout@v2
+         with:
+           fetch-depth: 0  # To reach the common commit
        - name: Setup git user as [bot]
          # Refs:
          # * https://github.community/t/github-actions-bot-email-address/17204/6
          # * https://github.com/actions/checkout/issues/13#issuecomment-724415212
          uses: fregante/setup-git-user@v1.0.1
 
+       - name: Switch to the translation source branch
+         run: |
+           sh -x
+
+           git fetch origin \
+             '+refs/heads/${{
+                 env.I18N_BRANCH
+             }}:refs/remotes/origin/${{
+                 env.SRC_BRANCH
+             }}'
+
+           git checkout -B '${{ env.I18N_BRANCH }}' \
+             'origin/${{ env.I18N_BRANCH }}'
+
+       - name: >-
+           Merge '${{ github.event.repository.default_branch }}'
+           to '${{ env.I18N_BRANCH }}'
+         run: |
+           sh -x
+
+           git merge '${{ github.event.repository.default_branch }}'
+
        - name: Set up Python
          uses: actions/setup-python@v2
          with:
@@ -37,15 +64,12 @@ jobs:
        - name: Commit the POT file to Git
          run: |
            git_hash=$(git rev-parse --short "${GITHUB_SHA}")
-           git commit -m "Update messages.pot as of version ${git_hash}" locales/messages.pot
-
-       - name: Check if any sources have changed since the last update
-         if: failure()
-         run: echo "There are no changes to the RST sources since the last update. Nothing to do."
+           git commit \
+             -m "Update messages.pot as of version ${git_hash}" \
+             locales/messages.pot
 
        - name: >-
-           Push the updated POT file back to
-           ${{ github.repository }}@${{ github.event.repository.default_branch }}
-           on GitHub
+           Push the updated POT file back to '${{ env.I18N_BRANCH }}'
+           branch on GitHub
          run: |
-           git push --atomic origin HEAD:${{ github.event.repository.default_branch }}
+           git push --atomic origin 'HEAD:${{ env.I18N_BRANCH }}'