轉自：http://zurb.com/forrst/posts/Displaying_the_Git_branch_in_your_BASH_prompt-iLv
把下面代碼放到～/.bash_profile 中

function find_git_branch {
 local dir=. head
 until [ "$dir" -ef / ]; do
 if [ -f "$dir/.git/HEAD" ]; then
 head=$(< "$dir/.git/HEAD")
 if [[ $head == ref:\ refs/heads/* ]]; then
 git_branch="[${head#*/*/}]"
 elif [[ $head != '' ]]; then
 git_branch='(detached)'
 else 
 git_branch='(unknown)'
 fi 
 return
 fi 
 dir="../$dir"
 done
 git_branch=''
}
PROMPT_COMMAND="find_git_branch; $PROMPT_COMMAND"
red=$'\e[31m'
normal_colours=$'\e[m'
 
PS1="\[$red\]\$git_branch\[$normal_colours\] \w \$ "