[postprocessor:ugoira] enable 'mtime' by default (#2714)

docs/configuration.rst

@@ -3567,7 +3567,7 @@ ugoira.mtime
 Type
     ``bool``
 Default
-    ``false``
+    ``true``
 Description
     Set modification times of generated ugoira aniomations.
 

gallery_dl/option.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2017-2021 Mike Fährmann
+# Copyright 2017-2022 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as

gallery_dl/postprocessor/ugoira.py

@@ -35,7 +35,7 @@ class UgoiraPP(PostProcessor):
         self.output = options.get("ffmpeg-output", True)
         self.delete = not options.get("keep-files", False)
         self.repeat = options.get("repeat-last-frame", True)
-        self.mtime = options.get("mtime")
+        self.mtime = options.get("mtime", True)
 
         ffmpeg = options.get("ffmpeg-location")
         self.ffmpeg = util.expand_path(ffmpeg) if ffmpeg else "ffmpeg"