Customize Bash PS1 prompt to show current status of active Git branch

bash.git-prompt.sh

# Customize Bash PS1 prompt to show current status of active Git branch.
# Adapted from and inspired by http://mediadoneright.com/content/ultimate-git-ps1-bash-prompt
# Slightly faster prompt, as measured on my machine (TM)
#
# By @muendelezaji, Oct 2015

# Skip if in zsh
[ "$ZSH" ] && return 0

# SETUP CONSTANTS
# Bunch-o-predefined colors.  Makes reading code easier than escape sequences.
# I don't remember where I found this.  o_O

# 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
# See: more: http://www.cyberciti.biz/tips/howto-linux-unix-bash-shell-setup-prompt.html
Time12hms="\T"
Time12ap="\@"
PathShort="\W"
PathFull="\w"
NewLine="\n"
Jobs="\j"
Time24hm="\A"
Time24hms="\t"
HostShort="\h"
HostFull="\H"

# Shorten path to first character of folder e.g. ref logs for git repo: ~/r/.g/l/refs
# See: http://unix.stackexchange.com/a/275016
PathShorter='$(sed -- "s:\([^/\.]\)[^/]*/:\1/:g" <<< ${PWD/#$HOME/\~})'

# Extra config options to indicate branch status, see:
# https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh
# Note: Might slow down the prompt!

# Show unstaged (*) and staged (+) changes
GIT_PS1_SHOWDIRTYSTATE=1

# Show if something is stashed '$'
GIT_PS1_SHOWSTASHSTATE=1

# Show if there are untracked files '%'
GIT_PS1_SHOWUNTRACKEDFILES=1

# Set to "auto" to show difference between HEAD and its upstream.
# A "<" indicates you are behind, ">" indicates you are ahead,
# "<>" indicates you have diverged and "=" indicates that there is no difference.
# You can also append "verbose" to show number of commits ahead/behind (+/-).
# GIT_PS1_SHOWUPSTREAM="auto"

# * = modified
# + = staged
# $ = stashed
# % = untracked
export PS1='$(if git symbolic-ref HEAD &>/dev/null; then\
      ps1=$(__git_ps1 "(%s)");\
      [[ $ps1 =~ [%*+] ]] && Color_On="'$IRed'" || Color_On="'$Green'";\
    fi;\
    echo "$Color_On$ps1'$Color_Off$Cyan[$PathShorter]\$$Color_Off'") '

# Alternative algo - use grep instead of bash's =~ (arguably more portable?)
# export PS1='$(if git symbolic-ref HEAD &>/dev/null; then\
#       echo $(__git_ps1 "(%s)") | grep -E [%*+] &>/dev/null;\
#       [ $? == 0 ] && Color_On="'$IRed'" || Color_On="'$Green'";\
#     fi;\
#     echo "$Color_On$ps1'$Color_Off$Cyan[$PathShort]\$$Color_Off'") '

# Can also replace 'symbolic-ref HEAD' with 'rev-parse --is-inside-work-tree' (likely slower)