Document maybeLstat

Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>

src/libutil/file-system.hh

@@ -84,6 +84,10 @@ bool isDirOrInDir(std::string_view path, std::string_view dir);
  */
 struct stat stat(const Path & path);
 struct stat lstat(const Path & path);
+/**
+ * `lstat` the given path if it exists.
+ * @return std::nullopt if the path doesn't exist, or an optional containing the result of `lstat` otherwise
+ */
 std::optional<struct stat> maybeLstat(const Path & path);
 
 /**