bundle2: introduce a bundleoperation object

bundle2: introduce a bundleoperation object

This object will hold all data and state gathered through the processing of a
bundle. This will allow:

- each handler to be aware of the things unbundled so far
- the caller to retrieve data about the execution
- bear useful object and logic (like repo, transaction)
- bear possible bundle2 reply triggered by the unbundling.

For now the object is very simple but it will grow at the same time as the
bundle2 implementation.

--- a/mercurial/bundle2.py	Wed Apr 02 13:50:57 2014 -0700
+++ b/mercurial/bundle2.py	Wed Apr 02 22:24:44 2014 -0700
@@ -183,6 +183,26 @@
         return func
     return _decorator
 
+class bundleoperation(object):
+    """an object that represents a single bundling process
+
+    Its purpose is to carry unbundle-related objects and states.
+
+    A new object should be created at the beginning of each bundle processing.
+    The object is to be returned by the processing function.
+
+    The object has very little content now it will ultimately contain:
+    * an access to the repo the bundle is applied to,
+    * a ui object,
+    * a way to retrieve a transaction to add changes to the repo,
+    * a way to record the result of processing each part,
+    * a way to construct a bundle response when applicable.
+    """
+
+    def __init__(self, repo):
+        self.repo = repo
+        self.ui = repo.ui
+
 def processbundle(repo, unbundler):
     """This function process a bundle, apply effect to/from a repo
 
@@ -194,7 +214,7 @@
 
     Unknown Mandatory part will abort the process.
     """
-    ui = repo.ui
+    op = bundleoperation(repo)
     # todo:
     # - replace this is a init function soon.
     # - exception catching
@@ -207,17 +227,17 @@
             key = parttype.lower()
             try:
                 handler = parthandlermapping[key]
-                ui.debug('found an handler for part %r\n' % parttype)
+                op.ui.debug('found a handler for part %r\n' % parttype)
             except KeyError:
                 if key != parttype: # mandatory parts
                     # todo:
                     # - use a more precise exception
                     raise
-                ui.debug('ignoring unknown advisory part %r\n' % key)
+                op.ui.debug('ignoring unknown advisory part %r\n' % key)
                 # todo:
                 # - consume the part once we use streaming
                 continue
-            handler(repo, part)
+            handler(op, part)
     except Exception:
         for part in iterparts:
             pass # consume the bundle content

--- a/tests/test-bundle2.t	Wed Apr 02 13:50:57 2014 -0700
+++ b/tests/test-bundle2.t	Wed Apr 02 22:24:44 2014 -0700
@@ -21,11 +21,11 @@
   > assert len(ELEPHANTSSONG) == 178 # future test say 178 bytes, trust it.
   > 
   > @bundle2.parthandler('test:song')
-  > def songhandler(repo, part):
+  > def songhandler(op, part):
   >     """handle a "test:song" bundle2 part, printing the lyrics on stdin"""
-  >     repo.ui.write('The choir start singing:\n')
+  >     op.ui.write('The choir starts singing:\n')
   >     for line in part.data.split('\n'):
-  >         repo.ui.write('    %s\n' % line)
+  >         op.ui.write('    %s\n' % line)
   > 
   > @command('bundle2',
   >          [('', 'param', [], 'stream level parameter'),