Merge pull request #101 from google/ojarjur/unshallow-mirror-workflow

Make the PR-mirroring workflow use the entire history of the current branch

.github/workflows/mirror-pull-requests.yaml

@@ -27,6 +27,7 @@ jobs:
 
       - name: Fetch upstream refs
         run: |
+          git fetch origin --unshallow
           git fetch origin '+refs/heads/*:refs/remotes/origin/*'
           git fetch origin '+refs/heads/master:refs/heads/master' || git pull
           git fetch origin '+refs/tags/*:refs/tags/*'