prompt
------

fast prompt helper tool to fetch vcs & cwd information, for
use with tmux:


   set -g  status-left "#(prompt cwd #{pane_current_path})"
   set -ag status-left "#(prompt vcs #{pane_current_path})"


usage
-----

    prompt cwd <some_path>
          Compresses some_path and stripes $HOME from its
          prefix

    prompt vcs <some_path>
          Fetches git ref (branch shorthand/commit OID),
          repo file statuses and commit distance
          information