Add formatting test workflow

tests/test-format.sh

@@ -0,0 +1,37 @@
+#!/bin/sh
+
+set -e
+
+[ -z "$1" ] && exit
+
+basebranch=$1
+
+CHANGED_FILES=$(git diff --name-only "$basebranch"...HEAD)
+
+CHANGED=0
+
+for file in $CHANGED_FILES
+do
+  case "$file" in
+  *.cpp|*.h)
+    echo Checking "$file"
+    clang-format -i "$file"
+    if ! git diff --quiet "$basebranch"...HEAD
+    then
+      printf "\033[31mError:\033[0m Formatting error in %s\n" "$file"
+      CHANGED=1
+      git add "$file"
+      git commit -q -m "Apply clang-format to $(basename "$file")"
+      printf "Creating patch "
+      git format-patch HEAD~
+    fi
+  esac
+done
+
+if [ $CHANGED = 1 ]
+then
+  printf "\033[31mError:\033[0m Issues found. You may use the patches provided as artifacts to format the code."
+  exit 1
+fi
+
+exit 0