exchange: set 'treemanifest' param on pushed changegroups too stable

exchange: set 'treemanifest' param on pushed changegroups too

In 5c0fd878779c (treemanifests: set bundle2 part parameter indicating
treemanifest, 2016-01-08), I didn't realize I had to set the parameter
separately for getbundle and unbundle. Having the parameter there on
push allows us to push to an empty repo and have the requirements
updated correctly.

--- a/mercurial/exchange.py	Mon Jan 25 11:37:02 2016 -0800
+++ b/mercurial/exchange.py	Fri Jan 22 16:31:50 2016 -0800
@@ -717,6 +717,8 @@
     cgpart = bundler.newpart('changegroup', data=cg)
     if version is not None:
         cgpart.addparam('version', version)
+    if 'treemanifest' in pushop.repo.requirements:
+        cgpart.addparam('treemanifest', '1')
     def handlereply(op):
         """extract addchangegroup returns from server reply"""
         cgreplies = op.records.getreplies(cgpart.id)

--- a/tests/test-treemanifest.t	Mon Jan 25 11:37:02 2016 -0800
+++ b/tests/test-treemanifest.t	Fri Jan 22 16:31:50 2016 -0800
@@ -312,9 +312,28 @@
    1
   +foo
 
+Pushing from treemanifest repo to an empty repo makes that a treemanifest repo
+
+  $ cd ..
+  $ hg init empty-repo
+  $ cat << EOF >> empty-repo/.hg/hgrc
+  > [experimental]
+  > changegroup3=yes
+  > EOF
+  $ grep treemanifest empty-repo/.hg/requires
+  [1]
+  $ hg push -R repo -r 0 empty-repo
+  pushing to empty-repo
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 2 changes to 2 files
+  $ grep treemanifest empty-repo/.hg/requires
+  treemanifest
+
 Create deeper repo with tree manifests.
 
-  $ cd ..
   $ hg --config experimental.treemanifest=True init deeprepo
   $ cd deeprepo