wireproto: drop the _decompress method in favor a new call type

wireproto: drop the _decompress method in favor a new call type

We already have multiple call function for multiple return type. The
`_decompress` function is only used for http and seems like a layer violation.
We drop it in favor of a new call type dedicated to "stream that may be useful to
compress".

--- a/mercurial/httppeer.py	Fri Mar 28 12:29:34 2014 -0700
+++ b/mercurial/httppeer.py	Fri Mar 28 14:24:13 2014 -0700
@@ -211,10 +211,8 @@
             fp.close()
             os.unlink(tempname)
 
-    def _abort(self, exception):
-        raise exception
-
-    def _decompress(self, stream):
+    def _callcompressable(self, cmd, **args):
+        stream =  self._callstream(cmd, **args)
         return util.chunkbuffer(zgenerator(stream))
 
 class httpspeer(httppeer):

--- a/mercurial/sshpeer.py	Fri Mar 28 12:29:34 2014 -0700
+++ b/mercurial/sshpeer.py	Fri Mar 28 14:24:13 2014 -0700
@@ -157,6 +157,9 @@
 
         return self.pipei
 
+    def _callcompressable(self, cmd, **args):
+        return self._callstream(cmd, **args)
+
     def _call(self, cmd, **args):
         self._callstream(cmd, **args)
         return self._recv()
@@ -176,8 +179,6 @@
             return '', r
         return self._recv(), ''
 
-    def _decompress(self, stream):
-        return stream
 
     def _recv(self):
         l = self.pipei.readline()

--- a/mercurial/wireproto.py	Fri Mar 28 12:29:34 2014 -0700
+++ b/mercurial/wireproto.py	Fri Mar 28 14:24:13 2014 -0700
@@ -314,16 +314,16 @@
 
     def changegroup(self, nodes, kind):
         n = encodelist(nodes)
-        f = self._callstream("changegroup", roots=n)
-        return changegroupmod.unbundle10(self._decompress(f), 'UN')
+        f = self._callcompressable("changegroup", roots=n)
+        return changegroupmod.unbundle10(f, 'UN')
 
     def changegroupsubset(self, bases, heads, kind):
         self.requirecap('changegroupsubset', _('look up remote changes'))
         bases = encodelist(bases)
         heads = encodelist(heads)
-        f = self._callstream("changegroupsubset",
-                             bases=bases, heads=heads)
-        return changegroupmod.unbundle10(self._decompress(f), 'UN')
+        f = self._callcompressable("changegroupsubset",
+                                   bases=bases, heads=heads)
+        return changegroupmod.unbundle10(f, 'UN')
 
     def getbundle(self, source, heads=None, common=None, bundlecaps=None):
         self.requirecap('getbundle', _('look up remote changes'))
@@ -334,8 +334,8 @@
             opts['common'] = encodelist(common)
         if bundlecaps is not None:
             opts['bundlecaps'] = ','.join(bundlecaps)
-        f = self._callstream("getbundle", **opts)
-        return changegroupmod.unbundle10(self._decompress(f), 'UN')
+        f = self._callcompressable("getbundle", **opts)
+        return changegroupmod.unbundle10(f, 'UN')
 
     def unbundle(self, cg, heads, source):
         '''Send cg (a readable file-like object representing the
@@ -388,6 +388,19 @@
         returns the server reply as a file like object."""
         raise NotImplementedError()
 
+    def _callcompressable(self, cmd, **args):
+        """execute <cmd> on the server
+
+        The command is expected to return a stream.
+
+        The stream may have been compressed in some implementaitons. This
+        function takes care of the decompression. This is the only difference
+        with _callstream.
+
+        returns the server reply as a file like object.
+        """
+        raise NotImplementedError()
+
     def _callpush(self, cmd, fp, **args):
         """execute a <cmd> on server
 
@@ -404,12 +417,6 @@
         """
         raise NotImplementedError()
 
-
-    def _decompress(self, stream):
-        """decompress a received stream
-        """
-        raise NotImplementedError()
-
 # server side
 
 # wire protocol command can either return a string or one of these classes.