ci(branch conventions): Make sure all PRs follow merge conventions

Author: amilcarlucas

.github/workflows/test_branch_conventions.yml

@@ -0,0 +1,64 @@
+name: Fail on Malformed Commits in PR Branch
+
+# brazenly copied from ArduPilot's test_branch_conventions.yml
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  check-merge-commits:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Harden the runner (Audit all outbound calls)
+        uses: step-security/harden-runner@95d9a5deda9de15063e7595e9719c11c38c90ae2 # v2.13.2
+        with:
+          egress-policy: audit
+
+      - name: Checkout PR branch
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
+        with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.event.pull_request.head.ref }}
+          fetch-depth: 0
+
+      - name: Fetch base branch
+        run: |
+          git remote -v
+          git remote add upstream ${{ github.event.pull_request.base.repo.clone_url }}
+          git fetch upstream ${{ github.base_ref }}
+          git show upstream/${{ github.base_ref }}
+
+      - name: Check for merge commits in PR branch
+        run: |
+          # Find merge-base between base branch and (rebased) PR branch
+          echo "Merge target is origin/${{ github.base_ref }}"
+          echo "github.event.pull_request.base.ref=${{ github.event.pull_request.base.ref }} "
+
+          # Look for merge commits in PR branch only
+          MERGE_COMMITS=$(git log upstream/${{ github.base_ref }}..HEAD --merges --oneline)
+          echo "Merge commits:"
+          echo "$MERGE_COMMITS"
+
+          if [[ -n "$MERGE_COMMITS" ]]; then
+            echo "❌ Merge commits detected in the PR branch (not allowed):"
+            echo "Please see https://github.com/ArduPilot/MethodicConfigurator/blob/master/CONTRIBUTING.md"
+            exit 1
+          else
+            echo "✅ No merge commits found in the PR branch."
+          fi
+
+          # Look for fixup! commits in PR branch only
+          COMMITS=$(git log upstream/${{ github.base_ref }}..HEAD --oneline)
+          echo "Commits:"
+          echo "$COMMITS"
+
+          if [[ "$COMMITS" == *"fixup!"* ]]; then
+            echo "❌ fixup commits detected in the PR branch (not allowed):"
+            echo "$COMMITS"
+            echo "Please see https://github.com/ArduPilot/MethodicConfigurator/blob/master/CONTRIBUTING.md"
+            exit 1
+          else
+            echo "✅ No fixup commits found in the PR branch."
+          fi

CONTRIBUTING.md

@@ -127,6 +127,7 @@ The review includes both automated checks and manual inspection.
   [Pyright](https://github.com/ArduPilot/MethodicConfigurator/actions/workflows/pyright.yml) validation
 * **Security Scanning**: Automated vulnerability detection via [CodeQL](https://github.com/ArduPilot/MethodicConfigurator/actions/workflows/codeql.yml) and dependency reviews
 * **Testing**: Comprehensive test suite execution with [pytest](https://github.com/ArduPilot/MethodicConfigurator/actions/workflows/pytest.yml)
+* **Git branching conventions**: Is the [pull request branch free of merge commits](https://github.com/ArduPilot/MethodicConfigurator/actions/workflows/test_branch_conventions.yml)?
 
 ### Manual Review Criteria
 
@@ -142,7 +143,6 @@ We manually verify the following aspects:
 * Do the [git commit messages follow conventional commit standards](https://www.conventionalcommits.org/en/v1.0.0/)?
 * Is at least the last commit in the pull request branch [signed off](https://developercertificate.org/) by the contributor?
 * Does the pull request have a clear description of the changes and their rationale?
-* Is the pull request branch free of merge commits?
 
 #### Architecture & Design