Use util.always instead of creating a new lambda function in show_changeset

and simplify the expression.

mercurial/cmdutil.py

@@ -524,9 +524,7 b' def show_changeset(ui, repo, opts, buffe'
     # options
     patch = False
     if opts.get('patch'):
-        patch = lambda x: True
-        if matchfn:
-            patch = matchfn
+        patch = matchfn or util.always
 
     br = None
     if opts.get('branches'):