bundle2: extract processing of part into its own function

This is code movement only. This will be useful to have it separated for reuse
purposes. We plan to introduce a new feature to the bundle format that allow
inserting a part in the middle of another part payload. This will be useful to
transmit a exception raised during a part generation.

mercurial/bundle2.py

@@ -292,6 +292,26 b' def processbundle(repo, unbundler, trans'
     part = None
     try:
         for part in iterparts:
+            _processpart(op, part)
+    except Exception, exc:
+        for part in iterparts:
+            # consume the bundle content
+            part.read()
+        # Small hack to let caller code distinguish exceptions from bundle2
+        # processing fron the ones from bundle1 processing. This is mostly
+        # needed to handle different return codes to unbundle according to the
+        # type of bundle. We should probably clean up or drop this return code
+        # craziness in a future version.
+        exc.duringunbundle2 = True
+        raise
+    return op
+
+def _processpart(op, part):
+    """process a single part from a bundle
+
+    The part is guaranteed to have been fully consumed when the function exits
+    (even if an exception is raised)."""
+    try:
             parttype = part.type
             # part key are matched lower case
             key = parttype.lower()
@@ -310,10 +330,7 b' def processbundle(repo, unbundler, trans'
                 if key != parttype: # mandatory parts
                     raise
                 op.ui.debug('ignoring unsupported advisory part %s\n' % exc)
-                # consuming the part
-                part.read()
-                continue
-
+            return # skip to part processing
 
             # handler is called outside the above try block so that we don't
             # risk catching KeyErrors from anything other than the
@@ -331,22 +348,10 b' def processbundle(repo, unbundler, trans'
             if output:
                 outpart = op.reply.newpart('b2x:output', data=output)
                 outpart.addparam('in-reply-to', str(part.id), mandatory=False)
-            part.read()
-    except Exception, exc:
-        if part is not None:
-            # consume the bundle content
-            part.read()
-        for part in iterparts:
-            # consume the bundle content
+    finally:
+        # consume the part content to not corrupt the stream.
             part.read()
-        # Small hack to let caller code distinguish exceptions from bundle2
-        # processing fron the ones from bundle1 processing. This is mostly
-        # needed to handle different return codes to unbundle according to the
-        # type of bundle. We should probably clean up or drop this return code
-        # craziness in a future version.
-        exc.duringunbundle2 = True
-        raise
-    return op
+
 
 def decodecaps(blob):
     """decode a bundle2 caps bytes blob into a dictionnary