sidedatacopies: only read from copies when in this mode

If we know we expect data from sidedata, we read them from sidedata and nothing
else.

This avoid looking into extra for revision without sidedata entries. Such
revision will be introduced in the next changesets.

Differential Revision: https://phab.mercurial-scm.org/D7067

mercurial/changelog.py

@@ -215,9 +215,10 b' class changelogrevision(object):'
         r'_offsets',
         r'_text',
         r'_sidedata',
+        r'_cpsd',
     )
 
-    def __new__(cls, text, sidedata):
+    def __new__(cls, text, sidedata, cpsd):
         if not text:
             return _changelogrevision(extra=_defaultextra)
 
@@ -250,6 +251,7 b' class changelogrevision(object):'
         self._offsets = (nl1, nl2, nl3, doublenl)
         self._text = text
         self._sidedata = sidedata
+        self._cpsd = cpsd
 
         return self
 
@@ -308,8 +310,10 b' class changelogrevision(object):'
 
     @property
     def filesadded(self):
-        if sidedatamod.SD_FILESADDED in self._sidedata:
+        if self._cpsd:
             rawindices = self._sidedata.get(sidedatamod.SD_FILESADDED)
+            if not rawindices:
+                return []
         else:
             rawindices = self.extra.get(b'filesadded')
         if rawindices is None:
@@ -318,8 +322,10 b' class changelogrevision(object):'
 
     @property
     def filesremoved(self):
-        if sidedatamod.SD_FILESREMOVED in self._sidedata:
+        if self._cpsd:
             rawindices = self._sidedata.get(sidedatamod.SD_FILESREMOVED)
+            if not rawindices:
+                return []
         else:
             rawindices = self.extra.get(b'filesremoved')
         if rawindices is None:
@@ -328,8 +334,10 b' class changelogrevision(object):'
 
     @property
     def p1copies(self):
-        if sidedatamod.SD_P1COPIES in self._sidedata:
+        if self._cpsd:
             rawcopies = self._sidedata.get(sidedatamod.SD_P1COPIES)
+            if not rawcopies:
+                return {}
         else:
             rawcopies = self.extra.get(b'p1copies')
         if rawcopies is None:
@@ -338,8 +346,10 b' class changelogrevision(object):'
 
     @property
     def p2copies(self):
-        if sidedatamod.SD_P2COPIES in self._sidedata:
+        if self._cpsd:
             rawcopies = self._sidedata.get(sidedatamod.SD_P2COPIES)
+            if not rawcopies:
+                return {}
         else:
             rawcopies = self.extra.get(b'p2copies')
         if rawcopies is None:
@@ -581,13 +591,18 b' class changelog(revlog.revlog):'
         ``changelogrevision`` instead, as it is faster for partial object
         access.
         """
-        c = changelogrevision(*self._revisiondata(node))
+        d, s = self._revisiondata(node)
+        c = changelogrevision(
+            d, s, self._copiesstorage == b'changeset-sidedata'
+        )
         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."""
         text, sidedata = self._revisiondata(nodeorrev)
-        return changelogrevision(text, sidedata)
+        return changelogrevision(
+            text, sidedata, self._copiesstorage == b'changeset-sidedata'
+        )
 
     def readfiles(self, node):
         """