commandserver: implement name() to clarify channel is not a plain file

Because unknown attributes are delegated to the underlying file object,
commandserver channels said they were '<stdout>' or '<stdin>' even though
they weren't. This patch makes them say '<X-channel>'.

mercurial/commandserver.py

@@ -43,6 +43,10 b' class channeledoutput(object):'
         self.out = out
         self.channel = channel
 
+    @property
+    def name(self):
+        return '<%c-channel>' % self.channel
+
     def write(self, data):
         if not data:
             return
@@ -75,6 +79,10 b' class channeledinput(object):'
         self.out = out
         self.channel = channel
 
+    @property
+    def name(self):
+        return '<%c-channel>' % self.channel
+
     def read(self, size=-1):
         if size < 0:
             # if we need to consume all the clients input, ask for 4k chunks