git tab completion and prompt in bash

.bash_profile

# Source the git-completion script.
# Your location may vary.
# If you don't have it, you can find it at
# https://github.com/git/git/blob/master/contrib/completion/git-completion.bash
source /usr/local/git/contrib/completion/git-completion.bash 

# If you want tab completion to work with your shell aliases for git, you'll have to do some extra work.
alias gco='git checkout'
complete -o default -o nospace -F _git_checkout gco

# And now the prompt.
# It will look like "current_working_directory ⚡ " if you're not in a git repo,
# and "current_working_directory (branchname) ⚡ " if you are.
export PS1='\W$(__git_ps1 " (%s)") ⚡ '

# Actually my prompt looks like this, with some color codes:
# export PS1="\[${BGreen}\]\W\$(__git_ps1 \" \[${BPurple}\](%s)\") \[${BIYellow}\]⚡ \[${Color_Off}\]"
# The color code constants are from http://wiki.archlinux.org/index.php/Color_Bash_Prompt .
# Note that the $ before the call to __git_ps1 is now escaped with a backslash to defer execution
# while still allowing the color constants to be executed once.