my custom bashprompt

.bashrc

##
# My custom bash prompt
#
# Mostly taken from Engineer Without a Cause:
# engineerwithoutacause.com/show-current-virtualenv-on-bash-prompt.html
#
# My tweak enables the "vim-tab-like shortpath"
##

# Everyone needs a little color in their lives
RED='\[\033[31m\]'
GREEN='\[\033[32m\]'
YELLOW='\[\033[33m\]'
BLUE='\[\033[34m\]'
PURPLE='\[\033[35m\]'
CYAN='\[\033[36m\]'
WHITE='\[\033[37m\]'
NIL='\[\033[00m\]'

# Hostname styles
FULL='\H'
SHORT='\h'

# System => color/hostname map:
# UC: username color
# LC: location/cwd color
# HD: hostname display (\h vs \H)
# Defaults:
UC=$GREEN
LC=$BLUE
HD=$FULL

# Prompt function because PROMPT_COMMAND is awesome
function set_prompt() {
    # show the host only and be done with it.
    host="${UC}${HD}${NIL}"

    # Special vim-tab-like shortpath (~/folder/directory/foo => ~/f/d/foo)
    _pwd=`pwd | sed "s:$HOME:~:" | sed "s:\(.\)[^/]*/:\1/:g"`
    if [[ $_pwd == "~" ]]; then
       _dirname=$_pwd
    else
       _dirname=`dirname "$_pwd" `
        if [[ $_dirname == "/" ]]; then
              _dirname=""
        fi
       _dirname="$_dirname/`basename "$_pwd"`"
    fi
    path="${LC}${_dirname}${NIL}"
    myuser="${UC}\u@${NIL}"

    # Dirtiness from:
    # http://henrik.nyh.se/2008/12/git-dirty-prompt#comment-8325834
    if git update-index -q --refresh 2>/dev/null; git diff-index --quiet --cached HEAD --ignore-submodules -- 2>/dev/null && git diff-files --quiet --ignore-submodules 2>/dev/null
        then dirty=""
    else
       dirty="${RED}*${NIL}"
    fi
    _branch=$(git symbolic-ref HEAD 2>/dev/null)
    _branch=${_branch#refs/heads/} # apparently faster than sed
    branch="" # need this to clear it when we leave a repo
    if [[ -n $_branch ]]; then
       branch=" ${NIL}[${PURPLE}${_branch}${dirty}${NIL}]"
    fi

    # Dollar/pound sign
    end="${LC}\$${NIL} "

    # Virtual Env
    if [[ $VIRTUAL_ENV != "" ]]
       then
           venv=" ${RED}(${VIRTUAL_ENV##*/})"
    else
       venv=''
    fi

    export PS1="${path}${venv}${branch} ${end}"
}

export PROMPT_COMMAND=set_prompt