revlog: drop base() again

deltaparent does what's needed, and more "portably".

mercurial/commands.py

@@ -1865,7 +1865,9 b' def debugrevlog(ui, repo, file_ = None, '
         ts = 0
         heads = set()
         for rev in xrange(numrevs):
-            dbase = r.base(rev)
+            dbase = r.deltaparent(rev)
+            if dbase == -1:
+                dbase = rev
             cbase = r.chainbase(rev)
             p1, p2 = r.parentrevs(rev)
             rs = r.rawsize(rev)

mercurial/revlog.py

@@ -320,8 +320,6 b' class revlog(object):'
         return self.start(rev) + self.length(rev)
     def length(self, rev):
         return self.index[rev][1]
-    def base(self, rev):
-        return self.index[rev][3]
     def chainbase(self, rev):
         index = self.index
         base = index[rev][3]