List hidden files if allowed (#3812)

Author: maxmouchet

notebook/services/contents/filemanager.py

@@ -334,7 +334,7 @@ def _dir_model(self, path, content=True):
                     self.log.debug("%s not a regular file", os_path)
                     continue
 
-                if self.should_list(name) and not is_file_hidden(os_path, stat_res=st):
+                if self.should_list(name) and ((not is_file_hidden(os_path, stat_res=st)) or self.allow_hidden):
                     contents.append(self.get(
                         path='%s/%s' % (path, name),
                         content=False)