tests/test-dirstate-backup.t

templates: split getgraphnode() body into two functions

getgraphnodecurrent() is checking if the node is currently checked out and
getgraphnodesymbol() is checking properties that have more to do with the
stored data and the DAG.

Set up

  $ hg init repo
  $ cd repo

Try to import an empty patch

  $ hg import --no-commit - <<EOF
  > EOF
  applying patch from stdin
  abort: stdin: no diffs found
  [255]

No dirstate backups are left behind

  $ ls .hg/dirstate* | sort
  .hg/dirstate