How to show git status info on the right side of the terminal?
PS1='$(printf "%*sr%s" $(( COLUMNS-1 )) "[$(git branch 2>/dev/null | grep '^*' | sed s/..//)] $(date +%H:%M:%S)" "heipei@wavefront:$PWD$ ")'

left="[${status}]u@h:w$ "
right="$(git symbolic-ref HEAD) $(date +%T)"
spaces="$(( $(tput cols) - ${#left} - ${#right} ))"
export PS1="$(printf "%s%${spaces}sn" "$left" "$right")"

preprompt() {
  rc=$?
  c=31
  [ $rc -eq 0 ] && c=32

  PS1="[$(color $c)]$rc[$(color 0)] t w $ "
  # right "prompt"
  # We cannot use $COLUMNS here, since in new shells the first prompt
  # will get garbled then. Seems like the correct value of COLUMNS is
  # in the shell init.
  printf "%`tput cols`s`tput cr`" "${USER}@${HOST}"
}

PROMPT_COMMAND=preprompt