3 "powerline-shell" (see https://github.com/milkbikis/powerline-shell)
8 - `POWERLINE_SHELL` ($HOME/powerline-shell.py; $HOME/.powerline-shell.py)
9 - `POWERLINE_SHELL_MODE` (compatible)
10 - `POWERLINE_SHELL_CWD_MODE` (fancy)
11 - `POWERLINE_SHELL_CWD_DEPTH` (4)
13 See `powerline-shell.py --help` for details.