Add mac support for pre-commit hook

Author: Apeiros-46B

scripts/githooks/pre-commit

@@ -5,14 +5,27 @@ filter_formattable_files() {
     grep -E '\.(h|cpp|c|cc|hpp|tpp|proto|py|md|yml)$|/BUILD$'
 }
 
+# Output the modification time of a file (or 0 if nonexistent)
+get_mtime() {
+    case "$(uname -s)" in
+        Darwin*)
+            stat -f %m "$1" 2> /dev/null || echo 0
+            ;;
+        *)
+            # No one will run this on BSD or other Unixes, so this should be fine
+            stat -c %Y "$1" 2> /dev/null || echo 0
+            ;;
+    esac
+}
+
 # Find repo root, marker for the current branch, and marker mtime (0 if marker does not exist)
 toplevel="$(git rev-parse --show-toplevel)"
 marker="$toplevel/scripts/.format_markers/$(git rev-parse --abbrev-ref HEAD)"
-mtime=$(stat -c %Y "$marker" 2> /dev/null || echo 0)
+mtime=$(get_mtime "$marker")
 
 git diff --staged --name-only | filter_formattable_files | while read -r file; do
     # Compare marker mtime with file mtime
-    if [ $mtime -lt "$(stat -c %Y "$toplevel/$file")" ]; then
+    if [ $mtime -lt $(get_mtime "$toplevel/$file") ]; then
         # The file was modified AFTER formatting. Remove the marker to tell the pre-push hook
         # that this commit introduces unformatted code.
         rm -f "$marker" 2> /dev/null