Source branch validation

.github/workflows/check-source-branch.yml

@@ -0,0 +1,94 @@
+name: Check PR Branch Origin
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  check-branch-origin:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Fetch all branches
+        run: |
+            git fetch origin
+            git fetch --all
+            git branch -r
+
+      - name: Check if branch was created from starlight-dev
+        run: |
+          PR_BRANCH="${{ github.head_ref }}"
+          HEAD_REPO="${{ github.event.pull_request.head.repo.full_name }}"
+          BASE_REPO="${{ github.event.pull_request.base.repo.full_name }}"
+
+          echo "PR Branch: $PR_BRANCH"
+          echo "Head repository: $HEAD_REPO"  
+          echo "Base repository: $BASE_REPO"
+
+          if [ "$HEAD_REPO" != "$BASE_REPO" ]; then
+            echo "Adding fork as remote..."
+            git remote add fork https://github.com/$HEAD_REPO.git
+            git fetch fork
+            FORK_BRANCH="fork/$PR_BRANCH"
+          else
+            FORK_BRANCH="origin/$PR_BRANCH"
+          fi
+
+          if ! git show-ref --verify --quiet refs/remotes/origin/starlight-dev; then
+            echo "Branch 'starlight-dev' not found in origin"
+            exit 1
+          fi
+
+          if ! git show-ref --verify --quiet refs/remotes/$FORK_BRANCH 2>/dev/null && ! git show-ref --verify --quiet refs/remotes/origin/$PR_BRANCH 2>/dev/null; then
+            echo "Branch '$PR_BRANCH' not found"
+            echo "Available branches:"
+            git branch -r
+            exit 1
+          fi
+
+          if git show-ref --verify --quiet refs/remotes/$FORK_BRANCH 2>/dev/null; then
+            BRANCH_REF=$FORK_BRANCH
+          else
+            BRANCH_REF="origin/$PR_BRANCH"
+          fi
+
+          echo "Using branch reference: $BRANCH_REF"
+
+          if ! BASE_COMMIT=$(git merge-base origin/starlight-dev $BRANCH_REF 2>/dev/null); then
+            echo "Could not find merge base between 'starlight-dev' and '$PR_BRANCH'"
+            exit 1
+          fi
+
+          echo "Base commit: $BASE_COMMIT"
+
+          if git merge-base --is-ancestor $BASE_COMMIT origin/starlight-dev; then
+            echo "Branch '$PR_BRANCH' was correctly created from 'starlight-dev'"
+          else
+            echo "Branch '$PR_BRANCH' was NOT created from 'starlight-dev'"
+            exit 1
+          fi
+
+      - name: Add comment on failure
+        if: failure()
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const body = `**Branch Origin Check Failed**
+
+            This pull request branch was not created from the \`starlight-dev\` branch. Please fix this before the PR can be merged.
+
+            **How to fix:**
+
+            **Rebase current branch:**
+            \`\`\`bash
+            git checkout your-branch-name
+            git rebase origin/starlight-dev
+            git push --force-with-lease
+            \`\`\`
+            `;
+