Improve UML workflow branch and PR handling (#581)

The workflow now deletes any existing 'update-uml-diagrams' branch locally and remotely before creating a new one, ensuring a clean state. PR creation will fail gracefully if a PR already exists, preventing errors in repeated runs.

Author: drbenvincent

.github/workflows/uml.yml

@@ -58,16 +58,25 @@ jobs:
       - name: Create PR for changes
         if: steps.changes.outputs.changes_exist == 'true'
         run: |
-          git checkout -b update-uml-diagrams
+          BRANCH_NAME="update-uml-diagrams"
+
+          # Delete the branch locally and remotely if it exists
+          git branch -D $BRANCH_NAME 2>/dev/null || true
+          git push origin --delete $BRANCH_NAME 2>/dev/null || true
+
+          # Create and push the new branch
+          git checkout -b $BRANCH_NAME
           git commit -m "Update UML Diagrams"
-          git push -u origin update-uml-diagrams
+          git push -u origin $BRANCH_NAME
+
+          # Create PR (will fail gracefully if PR already exists)
           gh pr create \
             --base main \
             --title "Update UML Diagrams" \
             --body "This PR updates the UML diagrams
             This PR was created automatically by the [UML workflow](https://github.com/pymc-labs/CausalPy/blob/main/.github/workflows/uml.yml).
             See the logs [here](https://github.com/pymc-labs/CausalPy/actions/workflows/uml.yml) for more details." \
             --label "no releasenotes" \
-            --reviewer drbenvincent
+            --reviewer drbenvincent || echo "PR may already exist"
         env:
           GH_TOKEN: ${{ github.token }}