bash PROMPT_COMMAND + PS1 for git status

.bash_ps1

#!/usr/bin/env bash

# copied from http://mediadoneright.com/content/ultimate-git-ps1-bash-prompt

#  Customize BASH PS1 prompt to show current GIT repository and branch.
#  by Mike Stewart - http://MediaDoneRight.com

# TODO: scope the following env vars to this file only. They can be seen with `declare -p`
# Reset
Color_Off="\[\033[0m\]"       # Text Reset
# Regular Colors
Black="\[\033[0;30m\]"        # Black
Red="\[\033[0;31m\]"          # Red
Green="\[\033[0;32m\]"        # Green
Yellow="\[\033[0;33m\]"       # Yellow
Blue="\[\033[0;34m\]"         # Blue
Purple="\[\033[0;35m\]"       # Purple
Cyan="\[\033[0;36m\]"         # Cyan
White="\[\033[0;37m\]"        # White
# Bold
# BBlack="\[\033[1;30m\]"       # Black
# BRed="\[\033[1;31m\]"         # Red
# BGreen="\[\033[1;32m\]"       # Green
# BYellow="\[\033[1;33m\]"      # Yellow
# BBlue="\[\033[1;34m\]"        # Blue
# BPurple="\[\033[1;35m\]"      # Purple
# BCyan="\[\033[1;36m\]"        # Cyan
# BWhite="\[\033[1;37m\]"       # White
# # Underline
# UBlack="\[\033[4;30m\]"       # Black
# URed="\[\033[4;31m\]"         # Red
# UGreen="\[\033[4;32m\]"       # Green
# UYellow="\[\033[4;33m\]"      # Yellow
# UBlue="\[\033[4;34m\]"        # Blue
# UPurple="\[\033[4;35m\]"      # Purple
# UCyan="\[\033[4;36m\]"        # Cyan
# UWhite="\[\033[4;37m\]"       # White
# # Background
# On_Black="\[\033[40m\]"       # Black
# On_Red="\[\033[41m\]"         # Red
# On_Green="\[\033[42m\]"       # Green
# On_Yellow="\[\033[43m\]"      # Yellow
# On_Blue="\[\033[44m\]"        # Blue
# On_Purple="\[\033[45m\]"      # Purple
# On_Cyan="\[\033[46m\]"        # Cyan
# On_White="\[\033[47m\]"       # White
# # High Intensty
# IBlack="\[\033[0;90m\]"       # Black
# IRed="\[\033[0;91m\]"         # Red
# IGreen="\[\033[0;92m\]"       # Green
# IYellow="\[\033[0;93m\]"      # Yellow
# IBlue="\[\033[0;94m\]"        # Blue
# IPurple="\[\033[0;95m\]"      # Purple
# ICyan="\[\033[0;96m\]"        # Cyan
# IWhite="\[\033[0;97m\]"       # White
# # Bold High Intensty
# BIBlack="\[\033[1;90m\]"      # Black
# BIRed="\[\033[1;91m\]"        # Red
# BIGreen="\[\033[1;92m\]"      # Green
# BIYellow="\[\033[1;93m\]"     # Yellow
# BIBlue="\[\033[1;94m\]"       # Blue
# BIPurple="\[\033[1;95m\]"     # Purple
# BICyan="\[\033[1;96m\]"       # Cyan
# BIWhite="\[\033[1;97m\]"      # White
# # High Intensty backgrounds
# On_IBlack="\[\033[0;100m\]"   # Black
# On_IRed="\[\033[0;101m\]"     # Red
# On_IGreen="\[\033[0;102m\]"   # Green
# On_IYellow="\[\033[0;103m\]"  # Yellow
# On_IBlue="\[\033[0;104m\]"    # Blue
# On_IPurple="\[\033[10;95m\]"  # Purple
# On_ICyan="\[\033[0;106m\]"    # Cyan
# On_IWhite="\[\033[0;107m\]"   # White

# Various variables you might want for your PS1 prompt instead
# Time12h="\T"
# Time12a="\@"
Time24h="\t"
# Time24hShort="\A"
PathShort="\w"
# PathFull="\W"
# NewLine="\n"
# Jobs="\j"

function __ps1_exit_indicator() {
  local EXIT="$1"
  if [[ $EXIT != "0" ]] && [[ $EXIT != "" ]]; then
    echo " [$EXIT]"
  fi
}

function gst_color() {
  if [ -z "$1" ]; then
    PS_GST_END='' # no git status
  elif ! \grep -o '^[^#]' <<< "$1" --quiet; then
    printf "${Green} (" # git status is clean
    PS_GST_END=')'
  # elif ! \grep -e '^[12#] [.][^.]' -e '^?' --quiet <<< "$1"; then
  #   printf "${Yellow} <" # all changes are staged
  #   PS_GST_END='>'
  else
    printf "${Red} [" # there are non-staged and/or untracked files, or unmerged changes
    PS_GST_END=']'
  fi
}
function gst_branch() {
  # `<<<` is a Here String (see http://www.tldp.org/LDP/abs/html/x17837.html)
  local branch=$(\grep '^# branch.head' <<< "$1" | cut -d' ' -f3 &)
  printf "$branch"
}
function gst_staged() {
  [ "$1" ] && local count=$(\grep -e '^[^#?] .[.]' --count <<< "$1" &) && [ "$count" != '0' ] && printf " +$count"
}
function gst_not_staged() {
  [ "$1" ] && local count=$(\grep -e '^[^#?] .[^.]' --count <<< "$1" &) && [ "$count" != '0' ] && printf " ~$count"
}
function gst_not_tracked() {
  [ "$1" ] && local count=$(\grep -e '^?' --count <<< "$1" &) && [ "$count" != '0' ] && printf " …$count"
}
function gst_any() {
  [ "$1" ] && ( ! \grep -e '^[^#]' --quiet <<< "$1" ) && printf ' ✓'
}
function gst_to_ps1() {
  local gst="$1"
  PS_GST_END=''
  # https://bashitout.com/2013/05/18/Ampersands-on-the-command-line.html
  gst_color "$gst"
  gst_branch "$gst" & \
    gst_staged "$gst" & \
    gst_not_staged "$gst" & \
    gst_not_tracked "$gst" & \
    gst_any "$gst"
  wait && echo "${PS_GST_END}"
}
function __prompt_command() {
  PS1=$Cyan$Time24h$Color_Off"\${_cmd_[\#]-$Purple\$(__ps1_exit_indicator \$?)}\${_cmd_[\#]=}"$Color_Off
  PS1+='/ \h:'$Blue$PathShort
  local gst=$(git status --porcelain=2 --branch 2> /dev/null)
  if [ "$gst" != "$PS_GST_CACHE" ]; then
    PS_GST_CACHE_GITPS1="$(gst_to_ps1 "$gst")"
  fi
  PS_GST_CACHE="$gst"
  PS1+="${PS_GST_CACHE_GITPS1}${Color_Off}"
  PS1+="\n🜚 "
}
function __prompt_command_no_cache() {
  PS_GST_CACHE=''
  __prompt_command
}
function __light_prompt_command() {
  PS1=$Cyan$Time24h$Color_Off"\${_cmd_[\#]-$Purple\$(__ps1_exit_indicator \$?)}\${_cmd_[\#]=}"$Color_Off
  PS1+='/ \h:'$Blue$PathShort$Color_Off'\n🜚 '
}
export PS_GST_CACHE=''
export PS_GST_CACHE_GITPS1=''
export PROMPT_COMMAND=__prompt_command