ERP5VCS: do not remove hidden files on export

product/ERP5VCS/WorkingCopy.py

@@ -407,6 +407,11 @@ class BusinessTemplateWorkingCopy(BusinessTemplateFolder):
           removed_set.add(d)
         del dirnames[i]
       for f in filenames:
+        # Ignore hidden files, at least for submodule support.
+        #  e.g. `.git` is a file pointing to the directory in its parent repo
+        #        <parent_repo>/.git/modules/<submodule>
+        #    or `.gitattributes`, etc.
+        if f[0] != '.':
           f = os.path.join(dirpath, f)
           if f not in self.file_set:
             os.remove(os.path.join(self.path, f))