Implement update_acl_on_path()

This allows to update or extend the existing ACL on path.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

pyacl/acl.py

@@ -243,6 +243,26 @@ def apply_acl_to_path(acl, path):
   acl.applyto(path)
 
 
+def update_acl_on_path(new_acl, path):
+  """
+  Example usage: update_acl_on_path(posix1e.ACL, '/etc/foo.txt')
+  Return: None
+  """
+  existing_acl = read_acl_from_path(path)
+  for entry in new_acl:
+    tag_type = entry.tag_type
+    if tag_type not in [ACL_USER_OBJ, ACL_GROUP_OBJ, ACL_OTHER, ACL_MASK]:
+      if tag_type in [ACL_USER, ACL_GROUP]:
+        for existing_entry in existing_acl:
+          if tag_type == existing_entry.tag_type:
+            if entry.qualifier == existing_entry.qualifier:
+              existing_acl.delete_entry(existing_entry)
+      existing_acl.append(entry)
+
+  acl = existing_acl
+  return apply_acl_to_path(acl, path)
+
+
 def read_acl_from_path(path):
   """
   Example usage: read_acl_from_path('/etc/foo.txt')