Update update-release-branch.py to take token from stdin

.github/update-release-branch.py

@@ -16,12 +16,23 @@ No user facing changes.
 """
 
 # NB: This exact commit message is used to find commits for reverting during backports.
-# Changing it requires a transition period where both old and new versions are supported.
+# Changing it requires a transition period where both old and new versions are supported.
 BACKPORT_COMMIT_MESSAGE = 'Update version and changelog for v'
 
 # Name of the remote
 ORIGIN = 'origin'
 
+# Environment variables to check for a GitHub API token.
+TOKEN_ENVIRONMENT_VARIABLES = ('GH_TOKEN', 'GITHUB_TOKEN')
+
+# Gets a GitHub API token from one of the supported environment variables.
+def get_github_token():
+  for variable_name in TOKEN_ENVIRONMENT_VARIABLES:
+    token = os.environ.get(variable_name, '').strip()
+    if token:
+      return token
+  raise Exception('Missing GitHub token. Set GITHUB_TOKEN or GH_TOKEN.')
+
 # Runs git with the given args and returns the stdout.
 # Raises an error if git does not exit successfully (unless passed
 # allow_non_zero_exit_code=True).
@@ -270,12 +281,6 @@ def update_changelog(version):
 def main():
   parser = argparse.ArgumentParser('update-release-branch.py')
 
-  parser.add_argument(
-    '--github-token',
-    type=str,
-    required=True,
-    help='GitHub token, typically from GitHub Actions.'
-  )
   parser.add_argument(
     '--repository-nwo',
     type=str,
@@ -313,7 +318,7 @@ def main():
   target_branch = args.target_branch
   is_primary_release = args.is_primary_release
 
-  repo = Github(args.github_token).get_repo(args.repository_nwo)
+  repo = Github(get_github_token()).get_repo(args.repository_nwo)
 
   # the target branch will be of the form releases/vN, where N is the major version number
   target_branch_major_version = target_branch.strip('releases/v')

.github/workflows/update-release-branch.yml

@@ -64,11 +64,12 @@ jobs:
 
     - name: Update current release branch
       if: github.event_name == 'workflow_dispatch'
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
         echo SOURCE_BRANCH=${REF_NAME}
         echo TARGET_BRANCH=releases/${MAJOR_VERSION}
         python .github/update-release-branch.py \
-          --github-token ${{ secrets.GITHUB_TOKEN }} \
           --repository-nwo ${{ github.repository }} \
           --source-branch '${{ env.REF_NAME }}' \
           --target-branch 'releases/${{ env.MAJOR_VERSION }}' \
@@ -107,11 +108,12 @@ jobs:
     - uses: ./.github/actions/release-initialise
 
     - name: Update older release branch
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
         echo SOURCE_BRANCH=${SOURCE_BRANCH}
         echo TARGET_BRANCH=${TARGET_BRANCH}
         python .github/update-release-branch.py \
-          --github-token ${{ secrets.GITHUB_TOKEN }} \
           --repository-nwo ${{ github.repository }} \
           --source-branch ${SOURCE_BRANCH} \
           --target-branch ${TARGET_BRANCH} \