tests/test-mq-qsave.t

scmutil: make cleanupnodes delete divergent bookmarks

cleanupnodes takes care of bookmark movement, and bookmark movement could
cause bookmark divergent resolution as a side effect. This patch adds such
bookmark divergent resolution logic so future rebase migration will be
easier.

The revset is carefully written to be equivalent to what rebase does today.
Although I think it might make sense to remove divergent bookmarks more
aggressively, for example:

    F   book@1
    |
    E   book@2
    |
    | D book
    | |
    | C
    |/
    B   book@3
    |
    A

When rebase -s C -d E, "book@1" will be removed, "book@3" will be kept,
and the end result is:

    D   book
    |
    C
    |
    F
    |
    E   book@2 (?)
    |
    B   book@3
    |
    A

The question is should we keep book@2? The current logic keeps it. If we
choose not to (makes some sense to me), the "deleterevs" revset could be
simplified to "newnode % oldnode".

For now, I just make it compatible with the existing behavior. If we want to
make the "deleterevs" revset simpler, we can always do it in the future.

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init

  $ echo 'base' > base
  $ hg ci -Ambase
  adding base

  $ hg qnew -mmqbase mqbase

  $ hg qsave
  $ hg qrestore 2
  restoring status: hg patches saved state