[PATCH 2 of 6 V3] merge: update comment for future devs

[Sean Farley]

# HG changeset patch
# User Sean Farley <sean.michael.farley at gmail.com>
# Date 1383755185 21600
#      Wed Nov 06 10:26:25 2013 -0600
# Node ID 32cd4060a08668fcde726193990bc59c4cc0356a
# Parent  8d89a657625079b8c4e530a37d18b20de89c380e
merge: update comment for future devs

diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -678,11 +678,13 @@ def update(repo, node, branchmerge, forc
     onode = node
     wlock = repo.wlock()
     try:
         wc = repo[None]
         if node is None:
-            # tip of current branch
+            # Here is where we should consider bookmarks, divergent bookmarks,
+            # foreground changesets (successors), and tip of current branch;
+            # but currently we are only checking the branch tips.
             try:
                 node = repo.branchtip(wc.branch())
             except error.RepoLookupError:
                 if wc.branch() == "default": # no default branch!
                     node = repo.lookup("tip") # update to tip