bundle2: add generic debug output regarding processed part payload

If we are about to hide the detailed debug output, we need some generic debug
message to replace it in a concise way.

mercurial/bundle2.py

@@ -1060,9 +1060,12 b' class unbundlepart(unpackermixin):'
             data = self._payloadstream.read()
         else:
             data = self._payloadstream.read(size)
+        self._pos += len(data)
         if size is None or len(data) < size:
+            if not self.consumed and self._pos:
+                self.ui.debug('bundle2-input-part: total payload size %i\n'
+                              % self._pos)
             self.consumed = True
-        self._pos += len(data)
         return data
 
     def tell(self):

tests/test-bundle2-format.t

@@ -500,6 +500,7 b' Test part'
       advisory: 0
   bundle2-input: payload chunk size: 178
   bundle2-input: payload chunk size: 0
+  bundle2-input-part: total payload size 178
       payload: 178 bytes
   bundle2-input: part header size: 22
   bundle2-input: part type: "test:debugreply"
@@ -519,6 +520,7 b' Test part'
       advisory: 1
   bundle2-input: payload chunk size: 2
   bundle2-input: payload chunk size: 0
+  bundle2-input-part: total payload size 2
       payload: 2 bytes
   bundle2-input: part header size: 29
   bundle2-input: part type: "test:song"
@@ -575,6 +577,7 b' Process the bundle'
   The choir starts singing:
   bundle2-input: payload chunk size: 178
   bundle2-input: payload chunk size: 0
+  bundle2-input-part: total payload size 178
       Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko
       Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
       Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.
@@ -594,6 +597,7 b' Process the bundle'
   bundle2-input-part: "test:math" (advisory) (params: 2 mandatory 2 advisory) unsupported-type
   bundle2-input: payload chunk size: 2
   bundle2-input: payload chunk size: 0
+  bundle2-input-part: total payload size 2
   bundle2-input: part header size: 29
   bundle2-input: part type: "test:song"
   bundle2-input: part id: "5"