Add check if git diff succeeded.

.github/workflows/clang-tidy.yml

@@ -10,7 +10,7 @@ jobs:
   analyze:
     runs-on: ubuntu-latest
 
-    name: Install clang-tidy
+    name: clang-tidy
     steps:
     - uses: actions/checkout@v3
     - name: Install clang-tidy

run-clang-tidy.sh

@@ -15,16 +15,32 @@ top_level=$(git rev-parse --show-toplevel)
 
 echo "\n\n###### REPORT\n\n"
 
-for modified in $(git diff --name-only origin/next); do
+git pull origin next
+changed_files=$(git diff --name-only origin/next)
+if [ $? -ne 0 ]; then
+  echo "Failed to get changed files."
+  exit 1
+fi
+
+for modified in changed_files; do
+  files_changed=1
   full_path="$top_level/$modified"
   if grep -q "$full_path" $tmp; then
     echo "$full_path as warnings. Please fix them."
     needs_fixes=1
   fi
 done
 
+if [ -z $files_changed ]; then
+  echo "No files changed."
+  exit 0
+fi
+
 if [ -z $needs_fixes ]; then
-  echo "All good"
+  echo "None of the changed files has clang-tidy warnings."
   exit 0
 fi
+
+echo "Some changed files have clang-tidy warnings. Please fix them. Or, if completely unrelated, let us know."
+
 exit 1