match: remove a mutable default argument

Mutable default arguments are know to the state of California to cause bugs. We
added support for None in the underlying function in the parent commit.
therefore we do not need to do anything but passing None.

mercurial/scmutil.py

@@ -778,7 +778,8 b' def matchandpats(ctx, pats=(), opts=None'
         pats = []
     return m, pats
 
-def match(ctx, pats=(), opts={}, globbed=False, default='relpath', badfn=None):
+def match(ctx, pats=(), opts=None, globbed=False, default='relpath',
+          badfn=None):
     '''Return a matcher that will warn about bad matches.'''
     return matchandpats(ctx, pats, opts, globbed, default, badfn=badfn)[0]