How do I remove the extra bash-3.2$ from shell-mode?

[Andrew Pennebaker]

Help, the first line of my shell-mode has an extra bash-3.2$ prompt before
my git prompt.

I tried writing PROMPT_COMMAND= in my ~/.bashrc according to an earlier
Stack Overflow post, but bash-3.2$ continues to display anyway.

M-x shell-mode RET

Expected:

    dotfiles (master)$ RET
    dotfiles (master)$ RET
    dotfiles (master)$ RET

Observed:

    bash-3.2$ dotfiles (master)$ RET
    dotfiles (master)$ RET
    dotfiles (master)$ RET

Configuration:

* https://github.com/mcandre/dotfiles/blob/master/.emacs
* https://github.com/mcandre/dotfiles/blob/master/.emacs_bash
* https://github.com/mcandre/dotfiles/blob/master/.bash_profile
* https://github.com/mcandre/dotfiles/blob/master/.bashrc
* https://github.com/mcandre/dotfiles/tree/master/.bashrc.d
* https://github.com/mcandre/dotfiles/tree/master/.bash_profile.d

System:

* emacs 24.4.1
* bash 3.2.57
* Mac OS X 10.10.3

-- 
Cheers,
Andrew