Pretty-print prompt when in a git repo

git_prompt

#
# 25 jul 2014
# 
# display the current git repository and some important stats in the shell prompt
#
# stick this in bashrc or wherever such tweaks are executed.
#
# Most code taken from http://vvv.tobiassjosten.net/bash/dynamic-prompt-with-git-and-ansi-colors/
#
# tweaked to put on a couple of lines, along with an edited directory path prompt
# (taken, naturally enough, from stackoverflow: http://stackoverflow.com/questions/5687446/bash-custom-ps1-with-nice-working-directory-path)
#   (couldn't use PROMPT_DIRTRIM on OS X as bash is too old)
#
# Also shows:
#    user.email (so I can remember whether I'm signing commits as me, or as me @ work)
#    unpushed commits (so that I remember to actually share my work)
#
# final prompt looks something like this:

# 
# ~/Work/.../Current/some-test-in-progress
# [[email protected]|master:1]
# $

# Dirty bits ("master" and ":1") are in red. well, magenta. 
#    (where "dirty" means things that aren't committed or pushed).
#
# If the current folder isn't a .git repo, then the entire git subline simply isn't shown.
#
# I also have a leading blank line and put the $ prompt at the left margin to make 
# things easier to read, and to give me lots of space for entering long commands.
#
# Most people will probably hate that.
#


# Configure colors, if available.
if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
  c_reset='\[\e[0m\]'
  c_user='\[\e[1;33m\]'
  c_path='\[\e[0;34m\]'
  c_git_cleancleann='\[\e[0;36m\]'
  c_git_dirty='\[\e[0;35m\]'
else
  c_reset=
  c_user=
  c_git_cleancleann_path=
  c_git_clean=
  c_git_dirty=
fi

# Function to assemble the Git parsingart of our prompt.
git_prompt ()
{
  if ! git rev-parse --git-dir > /dev/null 2>&1; then
    return 0
  fi

  git_branch=$(git branch 2>/dev/null | sed -n '/^\*/s/^\* //p')
  git_user=$(git config user.email 2>/dev/null)

  if git diff --quiet 2>/dev/null >&2; then
    git_color="$c_git_clean"
  else
    git_color="$c_git_dirty"
  fi
  unpushed=`git status | grep 'ahead of' | awk '{printf("%s",$(NF-1))}' 2>/dev/null`

  if [ ! -z $unpushed ]; then
    git_unpushed=${c_git_dirty}:$unpushed${c_reset}
  else
    git_unpushed=''
  fi

  echo "\n[${c_user}$git_user${c_reset}|$git_color$git_branch${c_reset}$git_unpushed]"
}

#
# trim prompt folder list
#
export MYPS='$(echo -n "${PWD/#$HOME/~}" | awk -F "/" '"'"'{
if (length($0) > 14) { if (NF>3) print $1 "/" $2 "/.../" $(NF-1) "/" $NF;
else if (NF>3) print $1 "/" $2 "/.../" $NF;
else print $1 "/.../" $NF; }
else print $0;}'"'"')'

# Thy holy prompt.
PROMPT_COMMAND='PS1="\n${c_path}${MYPS}${c_reset}$(git_prompt)\n\$ "'