pull: introduce a pulloperation object

pull: introduce a pulloperation object

This object will hold all data and state gathered through the pull. This will
allow us to split the long function into multiple small one. Smaller function
will be easier to maintains and wrap.  The idea is to blindly store all
information related to the pull in this object so that each step and extension
can use them if necessary.

We start by putting the `repo` variable in the object. More migration in other
function.

--- a/mercurial/exchange.py	Mon Jan 27 21:39:25 2014 +0100
+++ b/mercurial/exchange.py	Thu Jan 30 17:24:49 2014 -0800
@@ -373,10 +373,23 @@
         else:
             ui.warn(_('updating bookmark %s failed!\n') % b)
 
+class pulloperation(object):
+    """A object that represent a single pull operation
+
+    It purpose is to carry push related state and very common operation.
+
+    A new should be created at the begining of each push and discarded
+    afterward.
+    """
+
+    def __init__(self, repo):
+        # repo we pull from
+        self.repo = repo
 
 def pull(repo, remote, heads=None, force=False):
+    pullop = pulloperation(repo)
     if remote.local():
-        missing = set(remote.requirements) - repo.supported
+        missing = set(remote.requirements) - pullop.repo.supported
         if missing:
             msg = _("required features are not"
                     " supported in the destination:"
@@ -387,18 +400,18 @@
     # rollback call
     tr = None
     trname = 'pull\n' + util.hidepassword(remote.url())
-    lock = repo.lock()
+    lock = pullop.repo.lock()
     try:
-        tmp = discovery.findcommonincoming(repo.unfiltered(), remote,
+        tmp = discovery.findcommonincoming(pullop.repo.unfiltered(), remote,
                                            heads=heads, force=force)
         common, fetch, rheads = tmp
         if not fetch:
-            repo.ui.status(_("no changes found\n"))
+            pullop.repo.ui.status(_("no changes found\n"))
             result = 0
         else:
-            tr = repo.transaction(trname)
+            tr = pullop.repo.transaction(trname)
             if heads is None and list(common) == [nullid]:
-                repo.ui.status(_("requesting all changes\n"))
+                pullop.repo.ui.status(_("requesting all changes\n"))
             elif heads is None and remote.capable('changegroupsubset'):
                 # issue1320, avoid a race if remote changed after discovery
                 heads = rheads
@@ -415,7 +428,7 @@
                                        "changegroupsubset."))
             else:
                 cg = remote.changegroupsubset(fetch, heads, 'pull')
-            result = repo.addchangegroup(cg, 'pull', remote.url())
+            result = pullop.repo.addchangegroup(cg, 'pull', remote.url())
 
         # compute target subset
         if heads is None:
@@ -432,21 +445,21 @@
         publishing = bool(remotephases.get('publishing', False))
         if remotephases and not publishing:
             # remote is new and unpublishing
-            pheads, _dr = phases.analyzeremotephases(repo, subset,
+            pheads, _dr = phases.analyzeremotephases(pullop.repo, subset,
                                                      remotephases)
-            phases.advanceboundary(repo, phases.public, pheads)
-            phases.advanceboundary(repo, phases.draft, subset)
+            phases.advanceboundary(pullop.repo, phases.public, pheads)
+            phases.advanceboundary(pullop.repo, phases.draft, subset)
         else:
             # Remote is old or publishing all common changesets
             # should be seen as public
-            phases.advanceboundary(repo, phases.public, subset)
+            phases.advanceboundary(pullop.repo, phases.public, subset)
 
         def gettransaction():
             if tr is None:
-                return repo.transaction(trname)
+                return pullop.repo.transaction(trname)
             return tr
 
-        obstr = obsolete.syncpull(repo, remote, gettransaction)
+        obstr = obsolete.syncpull(pullop.repo, remote, gettransaction)
         if obstr is not None:
             tr = obstr