From IRC:
```
[05:46am] marlin_:
epriestley: hi mate! while i realize i am using this command wrongly, i thought to let you know about the undefined index warning:
[05:46am] marlin_:
$ arc backout D119
[05:46am] marlin_:
[2014-05-21 14:45:49] ERROR 8: Undefined index: callsign at [/Users/ml/dev/arcanist/arcanist/src/workflow/ArcanistBackoutWorkflow.php:128]
[05:46am] marlin_:
#0 ArcanistBackoutWorkflow::run() called at [/Users/ml/dev/arcanist/arcanist/scripts/arcanist.php:322]
[05:46am] phabot:
D119: Lint and unit star support. - https://secure.phabricator.com/D119
[05:46am] marlin_:
Usage Exception: Backout currently only supports Git and Mercurial
```