my_prompt.sh

#!/bin/bash

function __my_git_dirty {
  git diff --quiet 2>/dev/null || echo -e "*"
}

function __my_git_sha1 {
  sha1="$(git log --no-color -1 --pretty=format:%h 2>/dev/null)"
  if [ $? = 0 ]; then echo "$sha1"; fi
}

function __my_git_branch {
  str="$(/usr/lib/git-core/git-symbolic-ref HEAD 2>/dev/null)"
  if [ $? = 0 ]; then
    echo " (${str#refs/heads/}$(__my_git_dirty):$(__my_git_sha1))"
  fi
}

function __my_git_wd {
  gitdir="$(git rev-parse --git-dir 2>/dev/null)"

  if [ $? = 0 ]; then
    if [ "$(git config --get core.bare)" = "true" ]; then
      echo "$(basename "$(pwd)")"
    else
      if [ "$gitdir" = ".git" ]; then
        echo "$(basename "$PWD")"
      elif [ "$gitdir" = "." ]; then
        dir=$PWD
        while [ "$(basename $dir)" != ".git" ]; do
          dir=$(dirname $dir)
        done
        echo "$(basename $(dirname "$dir")) ${PWD#$(dirname "$dir")/}"
      else
        echo "${PWD#$(dirname $(dirname "$gitdir"))/}"
      fi
    fi
  else
    pwd | sed "s/\/home\//\~/"
  fi
}

export PS1='\[\e[G\e[1;${PC}m\]$(__my_git_wd)\[\e[0m\]$(__my_git_branch)`if [ $__RET -ne 0 ]; then echo " \e[1;41;37m $__RET \e[0m"; fi`\n↳ '

case "$TERM" in
xterm*|rxvt*)
  PROMPT_COMMAND='__RET=$?;echo -ne "\033]0;$USER@$HOSTNAME: $(__my_git_wd)$(__my_git_branch)\007"'
  ;;
esac