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doc/contributor/howto-guide-update-googleapis-sha.md

@@ -4,6 +4,15 @@ As of 11-07-2023, we are using a GHA to update the googleapis SHA. This runs
 once a week on Sundays and is generated by
 [updated-googleapis-sha](updated-googleapis-sha).
 
+To manually invoke the workflow, create a branch on the upstream repo with the
+prefix `ci-gha-googleapis`, and push an empty commit to it.
+
+```shell
+git checkout -b ci-gha-googleapis-circa-$(date +%Y-%m-%d)
+git commit --allow-empty
+git push
+```
+
 This document remains for anyone who wishes to perform the manual steps. This
 document describes the manual steps required to update the commit SHA for the
 [googleapis][googleapis-repo] repository. The document is intended for
@@ -54,4 +63,3 @@ git push --set-upstream origin "$(git branch --show-current)"
 Then use your favorite workflow to create the PR.
 
 [googleapis-repo]: https://github.com/googleapis/googleapis.git
-[updated-googleapis-sha]: https://github.com/googleapis/google-cloud-cpp/.github/workflows/update-googleapis-sha