Use most recent release when creating stable branch the first time

Refs #1, #2

Author: simonw

.github/workflows/stable-docs.yml

@@ -22,22 +22,27 @@ jobs:
       run: |
         git config user.name "Automated"
         git config user.email "[email protected]"
-
     - name: Check if stable branch exists
       run: |
         if ! git ls-remote --heads origin stable | grep stable; then
+          # Fetch all tags and sort them in descending order
+          LATEST_RELEASE=$(git tag | sort -Vr | head -n1)
+          # If no release is found, default to the main branch
+          if [ -z "$LATEST_RELEASE" ]; then
+            LATEST_RELEASE="main"
+          fi
+          # Check out the latest release or main branch
+          git checkout $LATEST_RELEASE
           git checkout -b stable
           git push -u origin stable
         fi
-
     - name: Handle Release
       if: github.event_name == 'release'
       run: |
         git fetch --all
         git checkout stable
         git reset --hard ${GITHUB_REF#refs/tags/}
         git push origin stable --force
-
     - name: Handle Commit to Main
       if: contains(github.event.head_commit.message, '!stable-docs')
       run: |