revlog: move flag checking out of the offset fastpath

mercurial/revlog.py

@@ -29,8 +29,6 b' class LookupError(RevlogError):'
     pass
 
 def getoffset(q):
-    if q & 0xFFFF:
-        raise RevlogError(_('incompatible revision flag %x') % q)
     return int(q >> 16)
 
 def gettype(q):
@@ -907,6 +905,10 b' class revlog(object):'
         rev = self.rev(node)
         base = self.base(rev)
 
+        # check rev flags
+        if self.index[rev][0] & 0xFFFF:
+            raise RevlogError(_('incompatible revision flag %x') % q)
+
         if self._inline:
             # we probably have the whole chunk cached
             df = None