Provide hooks so users can easily setup auto-commits, subscriber
notification, etc.  Probably either Darcs-style options:
  $ be COMMAND --help
  ...
    --posthook=COMMAND   Specify command to run after this command.
    --no-posthook        Do not run posthook command.
    --prompt-posthook    Prompt before running posthook. [DEFAULT]
    --run-posthook       Run posthook command without prompting.
  ...
or a Git-style hooks directory:
  $ tree .be
  .be/
  |-- version
  |-- hooks
  .   |-- post-commit.sh
  .   |-- pre-commit.sh
      `-- update.sh

