Merge branch 'rebase-i-comment-squash' into jk/pu

* branch rebase-i-comment-squash:
  rebase -i: comment first line of autosquashed message

Comment out the first line of a "!squash" commit when generating a
commit message in git-rebase.

Merged to jk/pu on 2013-03-30.  Dogfooding for a while to see if
this is a sensible change.
Merge branch 'rebase-upstream-reflog' into jk/pu

* branch rebase-upstream-reflog:
  rebase: use reflog to find common base with upstream

Use the reflog when no rebase root is specified so that we can do
better at avoiding conflicts when the upstream branch has been
rewritten.