add format check

.github/workflows/Java.yml

@@ -10,6 +10,17 @@ env:
   OVERRIDE_GIT_DESCRIBE: ${{ inputs.override_git_describe }}
 
 jobs:
+  format_check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          ref: ${{ inputs.git_ref }}
+
+      - run: make format-check
+
   java-linux-amd64:
     name: Java Linux (amd64)
     runs-on: ubuntu-latest

Makefile

@@ -42,5 +42,8 @@ release:
 format:
 	python3 scripts/format.py
 
+format-check:
+	python3 scripts/format.py --check
+
 clean:
 	rm -rf build

scripts/format.py

@@ -1,8 +1,17 @@
 from subprocess import check_call
 from os import scandir
 from glob import glob
+from argparse import ArgumentParser
+
+parser = ArgumentParser()
+parser.add_argument('--check', action='store_true')
+args = parser.parse_args()
+
+template = ['clang-format', '-i']
+if args.check:
+    template += ['--dry-run', '--Werror']
 
 for name in ['src/jni/duckdb_java.cpp'] + glob('src/**/*.java', recursive=True):
     print('Formatting', name)
-    check_call(['clang-format', '-i', name])
+    check_call(template + [name])