diff -r 8c121a9837ca -r d110167610db mercurial/cmdutil.py
--- a/mercurial/cmdutil.py	Thu Apr 12 23:24:33 2018 +0900
+++ b/mercurial/cmdutil.py	Thu Apr 12 23:25:58 2018 +0900
@@ -2231,7 +2231,7 @@
                 os.makedirs(os.path.dirname(filename))
             except OSError:
                 pass
-        with formatter.maybereopen(basefm, filename, opts) as fm:
+        with formatter.maybereopen(basefm, filename) as fm:
             _updatecatformatter(fm, ctx, matcher, path, opts.get('decode'))
 
     # Automation often uses hg cat on single files, so special case it