Add workflow automation for maintaining patched fork

.github/workflows/rebase-upstream.yml

@@ -0,0 +1,111 @@
+name: Rebase on Upstream
+
+on:
+  workflow_dispatch:
+  schedule:
+    # Run weekly on Mondays at 9am UTC
+    - cron: '0 9 * * 1'
+
+jobs:
+  rebase:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Setup git
+        run: |
+          git config user.name "GitHub Actions"
+          git config user.email "actions@github.com"
+
+      - name: Add upstream remote
+        run: |
+          git remote add upstream https://github.com/moby/buildkit.git || true
+          git fetch upstream master
+          git fetch origin master
+
+      - name: Rebase master on upstream
+        id: rebase
+        run: |
+          git checkout master
+
+          # Count our patches before rebase
+          BEFORE_COUNT=$(git rev-list upstream/master..HEAD --count)
+          echo "Patches before rebase: $BEFORE_COUNT"
+
+          # Perform rebase
+          if git rebase upstream/master; then
+            echo "✅ Rebase successful"
+
+            # Count our patches after rebase
+            AFTER_COUNT=$(git rev-list upstream/master..HEAD --count)
+            echo "Patches after rebase: $AFTER_COUNT"
+
+            # Check what changed
+            if [ "$BEFORE_COUNT" -ne "$AFTER_COUNT" ]; then
+              echo ""
+              echo "🎉 Patch count changed from $BEFORE_COUNT to $AFTER_COUNT"
+              echo "This likely means some of your patches were merged upstream!"
+            fi
+
+            # Push the rebased master
+            if ! git push origin master --force-with-lease; then
+              echo "❌ Rebase succeeded locally but failed to push to remote"
+              echo ""
+              echo "To push manually:"
+              echo "  git push origin master --force-with-lease"
+              echo ""
+              echo "rebase_status=failed" >> $GITHUB_OUTPUT
+              exit 1
+            fi
+
+            echo "✅ Successfully pushed rebased master to origin"
+            echo "rebase_status=success" >> $GITHUB_OUTPUT
+            echo "patch_count=$AFTER_COUNT" >> $GITHUB_OUTPUT
+          else
+            echo "❌ Rebase failed - manual intervention required"
+            echo ""
+            echo "To resolve manually:"
+            echo "1. git checkout master"
+            echo "2. git rebase upstream/master"
+            echo "3. Resolve conflicts"
+            echo "4. git push origin master --force-with-lease"
+
+            echo "rebase_status=failed" >> $GITHUB_OUTPUT
+            exit 1
+          fi
+
+      - name: Create issue on failure
+        if: failure()
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.issues.create({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              title: 'Manual rebase required: conflicts with upstream',
+              body: `The automated rebase on upstream has failed due to conflicts.
+
+            ## Action Required
+
+            Please manually rebase the master branch:
+
+            \`\`\`bash
+            git checkout master
+            git fetch upstream
+            git rebase upstream/master
+            # Resolve any conflicts
+            git push origin master --force-with-lease
+            \`\`\`
+
+            ## Workflow Run
+
+            [View failed workflow run](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }})
+
+            ---
+            *This issue was automatically created by the rebase workflow.*`,
+              labels: ['upstream-sync', 'needs-attention']
+            });