changegroup: fix treemanifest exchange code (issue5061)

There were two mistakes: one was accidental reuse of the fclnode
variable from the loop gathering file nodes, and the other (masked by
that bug) was not correctly handling deleted directories. Both cases
are now fixed and the test passes.

mercurial/changegroup.py

@@ -778,12 +778,15 @@ class cg1packer(object):
                 if 'treemanifest' in repo.requirements:
                     submfs = {'/': mdata}
                     for dn, bn in _moddirs(mfchangedfiles[x]):
-                        submf = submfs[dn]
-                        submf = submf._dirs[bn]
+                        try:
+                            submf = submfs[dn]
+                            submf = submf._dirs[bn]
+                        except KeyError:
+                            continue # deleted directory, so nothing to send
                         submfs[submf.dir()] = submf
                         tmfclnodes = tmfnodes.setdefault(submf.dir(), {})
-                        tmfclnodes.setdefault(submf._node, clnode)
-                        if clrevorder[clnode] < clrevorder[fclnode]:
+                        tmfclnode = tmfclnodes.setdefault(submf._node, clnode)
+                        if clrevorder[clnode] < clrevorder[tmfclnode]:
                             tmfclnodes[n] = clnode
                 return clnode
 

tests/test-treemanifest.t

@@ -332,6 +332,21 @@ Pushing from treemanifest repo to an empty repo makes that a treemanifest repo
   $ grep treemanifest empty-repo/.hg/requires
   treemanifest
 
+Pushing to an empty repo works
+
+  $ hg --config experimental.treemanifest=1 init clone
+  $ grep treemanifest clone/.hg/requires
+  treemanifest
+  $ hg push -R repo clone
+  pushing to clone
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 11 changesets with 15 changes to 10 files (+3 heads)
+  $ grep treemanifest clone/.hg/requires
+  treemanifest
+
 Create deeper repo with tree manifests.
 
   $ hg --config experimental.treemanifest=True init deeprepo