[PATCH 1 of 2] rebase: remove an unused todo

[Laurent Charignon]

# HG changeset patch
# User Laurent Charignon <lcharignon at fb.com>
# Date 1447891560 28800
#      Wed Nov 18 16:06:00 2015 -0800
# Node ID 476330c90ca0a7db3330c0f3674649ba5d6a98a9
# Parent  aa8771a01f32c86b4f9df8c45386bfe880a4e9dd
rebase: remove an unused todo

Since we handled skipping obsolete revs when it is relevant, this todo is no
longer useful. We replace the comment with two useful comments.

diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -30,8 +30,9 @@ import os, errno
 revtodo = -1
 nullmerge = -2
 revignored = -3
-# To do with obsolescence
+# successor in rebase destination
 revprecursor = -4
+# plain prune (no successor)
 revpruned = -5
 
 cmdtable = {}