manifest: move manifest creation to a helper function stable

manifest: move manifest creation to a helper function

A future patch will be moving manifest creation to be inside manifestlog as part
of improving our cache guarantees. bundlerepo and unionrepo currently rely on
being able to hook into manifest creation, so let's temporarily move the actual
manifest creation to a helper function for them to intercept.

In the future manifest.manifest() will disappear entirely and this can
disappear.

--- a/mercurial/bundlerepo.py	Tue Oct 18 14:27:30 2016 -0500
+++ b/mercurial/bundlerepo.py	Tue Oct 18 17:32:51 2016 -0700
@@ -343,8 +343,7 @@
         self.manstart = self.bundle.tell()
         return c
 
-    @localrepo.unfilteredpropertycache
-    def manifest(self):
+    def _constructmanifest(self):
         self.bundle.seek(self.manstart)
         # consume the header if it exists
         self.bundle.manifestheader()

--- a/mercurial/localrepo.py	Tue Oct 18 14:27:30 2016 -0500
+++ b/mercurial/localrepo.py	Tue Oct 18 17:32:51 2016 -0700
@@ -506,6 +506,12 @@
 
     @storecache('00manifest.i')
     def manifest(self):
+        return self._constructmanifest()
+
+    def _constructmanifest(self):
+        # This is a temporary function while we migrate from manifest to
+        # manifestlog. It allows bundlerepo and unionrepo to intercept the
+        # manifest creation.
         return manifest.manifest(self.svfs)
 
     @property

--- a/mercurial/unionrepo.py	Tue Oct 18 14:27:30 2016 -0500
+++ b/mercurial/unionrepo.py	Tue Oct 18 17:32:51 2016 -0700
@@ -208,8 +208,7 @@
         node = self.repo2.changelog.node(rev2)
         return self.changelog.rev(node)
 
-    @localrepo.unfilteredpropertycache
-    def manifest(self):
+    def _constructmanifest(self):
         return unionmanifest(self.svfs, self.repo2.svfs,
                              self.unfiltered()._clrev)