pull: reorganize bundle2 argument bundling

pull: reorganize bundle2 argument bundling

We are about to add the ability to use stream bundle with bundle2. Before doing
so, we need to gather some code that will not be used in the bundle2 case. There
is no behavior change within this changeset.

--- a/mercurial/exchange.py	Wed Jan 17 16:38:32 2018 +0100
+++ b/mercurial/exchange.py	Wed Jan 17 16:32:05 2018 +0100
@@ -1450,24 +1450,32 @@
     For now, the only supported data are changegroup."""
     kwargs = {'bundlecaps': caps20to10(pullop.repo)}
 
+    # make ui easier to access
+    ui = pullop.repo.ui
+
     # At the moment we don't do stream clones over bundle2. If that is
     # implemented then here's where the check for that will go.
     streaming = False
 
+    # declare pull perimeters
+    kwargs['common'] = pullop.common
+    kwargs['heads'] = pullop.heads or pullop.rheads
+
     # pulling changegroup
     pullop.stepsdone.add('changegroup')
 
-    kwargs['common'] = pullop.common
-    kwargs['heads'] = pullop.heads or pullop.rheads
     kwargs['cg'] = pullop.fetch
 
-    ui = pullop.repo.ui
     legacyphase = 'phases' in ui.configlist('devel', 'legacy.exchange')
     hasbinaryphase = 'heads' in pullop.remotebundle2caps.get('phases', ())
     if (not legacyphase and hasbinaryphase):
         kwargs['phases'] = True
         pullop.stepsdone.add('phases')
 
+    if 'listkeys' in pullop.remotebundle2caps:
+        if 'phases' not in pullop.stepsdone:
+            kwargs['listkeys'] = ['phases']
+
     bookmarksrequested = False
     legacybookmark = 'bookmarks' in ui.configlist('devel', 'legacy.exchange')
     hasbinarybook = 'bookmarks' in pullop.remotebundle2caps
@@ -1482,8 +1490,6 @@
         bookmarksrequested = True
 
     if 'listkeys' in pullop.remotebundle2caps:
-        if 'phases' not in pullop.stepsdone:
-            kwargs['listkeys'] = ['phases']
         if 'request-bookmarks' not in pullop.stepsdone:
             # make sure to always includes bookmark data when migrating
             # `hg incoming --bundle` to using this function.