Make run-clang-format.sh work well in before-submit and CI

In scripts/before-submit.sh, we do not want to get an error
when anything is formatted, we just want it to be done.

In the CI, however, we want to use the same script and have it
fail if not.

Author: hzeller

.github/workflows/ci.yml

@@ -67,19 +67,8 @@ jobs:
       - name: Run formatting style check
         run: |
           clang-format-18 --version
-          CLANG_FORMAT=clang-format-18 scripts/run-clang-format.sh
-          git diff > /tmp/format-diff
-          if [ -s "/tmp/format-diff" ]; then
-            echo "Difference to optimal formatting"
-            cat /tmp/format-diff
-            echo
-            echo "=================== To Fix ==========================="
-            echo "Run scripts/run-format.sh"
-            echo "then"
-            echo "  git commit -a --amend"
-            echo "  git push -f"
-            exit 1
-          fi
+          RUNNING_IN_CI=1 CLANG_FORMAT=clang-format-18 \
+            scripts/run-clang-format.sh
 
   ClangTidy:
     runs-on: ubuntu-24.04
@@ -117,4 +106,3 @@ jobs:
           clang-tidy-18 --version
           CLANG_TIDY=clang-tidy-18 scripts/run-clang-tidy-cached.cc \
             || ( cat fpga-assembler_clang-tidy.out ; exit 1)
-

scripts/run-clang-format.sh

@@ -6,6 +6,7 @@ FORMAT_OUT=${TMPDIR:-/tmp}/clang-format-diff.out
 
 CLANG_FORMAT=${CLANG_FORMAT:-clang-format}
 BUILDIFIER=${BUILDIFIER:-buildifier}
+RUNNING_IN_CI=${RUNNING_IN_CI:-0}
 
 ${CLANG_FORMAT} --version
 
@@ -19,17 +20,21 @@ if command -v ${BUILDIFIER} >/dev/null; then
   ${BUILDIFIER} -lint=fix MODULE.bazel $(find . -name BUILD -o -name "*.bzl")
 fi
 
-# Check if we got any diff
-git diff > ${FORMAT_OUT}
-
-if [ -s ${FORMAT_OUT} ]; then
-   echo "Style not matching"
-   echo "Run"
-   echo "  .github/bin/run-clang-format.sh"
-   echo "-------------------------------------------------"
-   echo
-   cat ${FORMAT_OUT}
-   exit 1
+# If in CI, we want to report changes, as we don't expect them
+if [ "$RUNNING_IN_CI" -eq 1 ]; then
+    # Check if we got any diff
+    git diff > ${FORMAT_OUT}
+
+    if [ -s ${FORMAT_OUT} ]; then
+	echo "Style not matching"
+	echo "Run"
+	echo "  scripts/run-clang-format.sh"
+	echo "and amend PR."
+	echo "-------------------------------------------------"
+	echo
+	cat ${FORMAT_OUT}
+	exit 1
+    fi
 fi
 
 exit 0