sidedatacopies: get and store sidedata in the changelogrevision object

sidedatacopies: get and store sidedata in the changelogrevision object

The object provide a simple way to access changelog entry, we need it to also
bear the sidedata value.

Since the sidedata are retrieved at the same time as the revision, we can do
that without extra cost.

Differential Revision: https://phab.mercurial-scm.org/D6951

--- a/mercurial/changelog.py	Sun Oct 06 23:36:51 2019 -0400
+++ b/mercurial/changelog.py	Sun Oct 06 23:36:51 2019 -0400
@@ -268,9 +268,10 @@
     __slots__ = (
         r'_offsets',
         r'_text',
+        r'_sidedata',
     )
 
-    def __new__(cls, text):
+    def __new__(cls, text, sidedata):
         if not text:
             return _changelogrevision(extra=_defaultextra)
 
@@ -302,6 +303,7 @@
 
         self._offsets = (nl1, nl2, nl3, doublenl)
         self._text = text
+        self._sidedata = sidedata
 
         return self
 
@@ -613,12 +615,13 @@
         ``changelogrevision`` instead, as it is faster for partial object
         access.
         """
-        c = changelogrevision(self.revision(node))
+        c = changelogrevision(*self._revisiondata(node))
         return (c.manifest, c.user, c.date, c.files, c.description, c.extra)
 
     def changelogrevision(self, nodeorrev):
         """Obtain a ``changelogrevision`` for a node or revision."""
-        return changelogrevision(self.revision(nodeorrev))
+        text, sidedata = self._revisiondata(nodeorrev)
+        return changelogrevision(text, sidedata)
 
     def readfiles(self, node):
         """