sshpeer: add a method to check if a doublepipe is closed

So we can tell in a next commit if we're trying to close an already
closed connection or not (in which case, we may warn).

Differential Revision: https://phab.mercurial-scm.org/D9996

mercurial/sshpeer.py

@@ -140,6 +140,10 b' class doublepipe(object):'
     def close(self):
         return self._main.close()
 
+    @property
+    def closed(self):
+        return self._main.closed
+
     def flush(self):
         return self._main.flush()
 

tests/test-check-interfaces.py

@@ -113,6 +113,10 b' class dummypipe(object):'
     def close(self):
         pass
 
+    @property
+    def closed(self):
+        pass
+
 
 def main():
     ui = uimod.ui()