Issue1678: IndexError when pushing

setting up base repo

  $ hg init a

  $ cd a

  $ touch a

  $ hg ci -Am a

  adding a

  $ cd ..

cloning base repo

  $ hg clone a b

  updating to branch default

  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd b

setting up cset to push

  $ hg up null

  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ touch a

different msg so we get a clog new entry

  $ hg ci -Am b

  adding a

  created new head

pushing

  $ hg push -f ../a

  pushing to ../a

  searching for changes

  adding changesets

  adding manifests

  adding file changes

  added 1 changesets with 0 changes to 0 files (+1 heads)

  $ cd ..