chore: allow releases from older version branches (#388)

* chore: allow releases from older version branches

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

.github/release-please.yml

@@ -1,2 +1,11 @@
 releaseType: python
 handleGHRelease: true
+# NOTE: this section is generated by synthtool.languages.python
+# See https://github.com/googleapis/synthtool/blob/master/synthtool/languages/python.py
+branches:
+- branch: v1
+  handleGHRelease: true
+  releaseType: python
+- branch: v0
+  handleGHRelease: true
+  releaseType: python

owlbot.py

@@ -16,6 +16,7 @@
 
 import synthtool as s
 from synthtool import gcp
+from synthtool.languages import python
 
 common = gcp.CommonTemplates()
 
@@ -47,5 +48,6 @@
 
 s.replace(".github/workflows/lint.yml", "python-version: \"3.10\"", "python-version: \"3.7\"")
 
+python.configure_previous_major_version_branches()
 
 s.shell.run(["nox", "-s", "blacken"], hide_output=False)