extensions: fix wrapcommand/function of class instance

5361771f9714 changed _updatewrapper() to copy the __name__ attribute, but
not all callable objects has __name__.

Spotted by loading mq with extdiff.

mercurial/extensions.py

@@ -333,7 +333,10 b' def bind(func, *args):'
 
 def _updatewrapper(wrap, origfn, unboundwrapper):
     '''Copy and add some useful attributes to wrapper'''
-    wrap.__name__ = origfn.__name__
+    try:
+        wrap.__name__ = origfn.__name__
+    except AttributeError:
+        pass
     wrap.__module__ = getattr(origfn, '__module__')
     wrap.__doc__ = getattr(origfn, '__doc__')
     wrap.__dict__.update(getattr(origfn, '__dict__', {}))

tests/test-extensions-wrapfunction.py

@@ -54,3 +54,11 b' with wrap1:'
         print('context manager', dummy.getstack())
     print('context manager', dummy.getstack())
 print('context manager', dummy.getstack())
+
+# Wrap callable object which has no __name__
+class callableobj(object):
+    def __call__(self):
+        return ['orig']
+dummy.cobj = callableobj()
+extensions.wrapfunction(dummy, 'cobj', wrappers[0])
+print('wrap callable object', dummy.cobj())

tests/test-extensions-wrapfunction.py.out

@@ -18,3 +18,4 b" context manager [0, 1, 'orig']"
 context manager [2, 0, 1, 'orig']
 context manager [2, 1, 'orig']
 context manager [2, 'orig']
+wrap callable object [0, 'orig']