While I understand that command line interface programmers don't feel like they need to adhere to the same rules as UI designers, I think it would be best if they reconsidered.
Under no circumstances is it necessary for an error message to tell me something was "fatal". It evokes feelings of panic and makes me feel as though I've done something irreversible. In the example above I simply called "git pull" (grab the latest code from the repository) on the wrong folder. Because that folder wasn't tracked by git, it doesn't do anything... it just exits.
Consider using another response, such as "Not a git repository, nothing has been pulled. Are you in the right directory?". I don't need to hear about what process was killed or how it died, I just want to know what happened and what I should do about it.
Thanks :)