Run Buildifier in CI

Author: dtolnay

.github/workflows/lint.yml

@@ -39,3 +39,19 @@ jobs:
       - uses: actions/checkout@v4
       - uses: dtolnay/install-buck2@latest
       - run: git ls-files '*.bzl' '*.bxl' | xargs buck2 starlark lint
+
+  buildifier:
+    name: Buildifier
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v4
+      - run: go install github.com/bazelbuild/buildtools/buildifier@latest
+      - run: echo $(go env GOPATH)/bin >> $GITHUB_PATH
+      - run: git ls-files '*.bzl' | xargs buildifier
+      - run: git ls-files '*/BUCK' BUCK_TREE | xargs -n1 buildifier -path BUILD.bazel -lint fix
+      - run: git ls-files '*.bxl' | xargs -n1 buildifier -path script.bzl -lint fix
+      - name: Check that buildifier wanted no changes
+        run: git diff --exit-code