Include this in your .bash_profile to get colors, info and autocompletion on your prompt (if git is installed via homebrew)

gistfile1.sh

# Git comes with some shell scripts you can load to get
# nifty shell features.  Homebrew sticks them in /usr/local/etc/bash_completion.d
source "/usr/local/etc/bash_completion.d/git-prompt.sh"
source "/usr/local/etc/bash_completion.d/git-completion.bash"
# apparently you can specify __git_ps1 as the thing that
# renders your prompt by setting PROMPT_COMMAND.
# Setting the PROMPT_COMMAND lets git display colors.
#
# The alternative is just to set the PS1 variable.
#
# the "\u@\h:\W" "\\\$ " bit says "
#   display the user, 
#   an @ sign, 
#   the hostname of your machine
#   a colon
#   the current directory
#   and then some git stuff
export PROMPT_COMMAND='__git_ps1 "\u@\h:\W" "\\\$ "'
# and we can tell it what to show us.
export GIT_PS1_SHOWDIRTYSTATE=1
export GIT_PS1_SHOWSTASHSTATE=1
export GIT_PS1_SHOWUNTRACKEDFILES=1
export GIT_PS1_SHOWUPSTREAM="auto"
export GIT_PS1_SHOWCOLORHINTS=true

It looks like this: