A bash prompt for your git status and more.

bash_prompt

#!/bin/bash

#  DESCRIPTION:
#  You might find this bash prompt useful if you make regular use of Git and
#  virtualenv.
#
#  FEATURES:
#  - Displays any activated virtualenv. 
#  - Displays the username and current working directory.
#  - Displays the current git branch, as well as the number of commits to
#    pull (red) or push (green). The colour of the branch name will also change 
#    depending on whether your working directory is clean (grey), has untracked
#    files with no other modifications (light blue), has unstaged changes
#    (yellow), has changes to be committed (dark orange), or if your local
#    branch has diverged from the remote (red).
#  - The prompt symbol is highlighted in red if the exit code of the last 
#    command was anything other than 0. 
#
#  INSTRUCTIONS:
#  1. Either move or symlink this file to ~/.bash_prompt
#  2. Add `source ~/.bash_prompt` to ~/.bash_profile or ~/.bashrc
# 
#  NOTES:
#  - The number of commits will not appear if you do not have an upstream
#    branch set for the current branch in your .gitconfig.
# 
#  ACKNOWLEDGEMENTS: 
#  - https://gist.github.com/insin/1425703


# colour codes
NONE="\[\033[0m\]"
RED="\[\033[0;31m\]"
GREEN="\[\033[0;32m\]"
YELLOW="\[\033[0;33m\]"
BLUE="\[\033[0;34m\]"
PURPLE="\[\033[0;35m\]"
LIGHT_BLUE="\[\033[0;36m\]"
LIGHT_GREY="\[\033[0;37m\]"

# 256 colour support
function fg_colour { echo -ne "\[\033[38;5;$1m\]"; }
function bg_colour { echo -ne "\[\033[48;5;$1m\]"; }


function set_titlebar {
    case $TERM in
        xterm*)
            TITLEBAR='\[\033]0;\w\007\]'
            ;;
        *)
            TITLEBAR=""
            ;;
    esac
}

function set_virtualenv {
    if [[ -z "$VIRTUAL_ENV" ]] ; then
        VIRTUALENV=""
    else
        VIRTUALENV="${LIGHT_GREY}{`basename \"$VIRTUAL_ENV\"`}"
        export PYLIB="$(python -c "import distutils; print distutils.sysconfig.get_python_lib()")"
    fi
}

function set_username {
    USERNAME="${GREEN}\u"
}

function set_current_working_directory {
    CWD="${LIGHT_GREY}\w"
}

# returns 0 if the current directory is a git repository
function is_git_repository {
    git branch &> /dev/null
}

# set current git branch 
function set_git_branch {
    branch_name="$(git branch --no-color 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/\1/')"
    git_status="$(git status 2> /dev/null)"

    if [[ ${git_status} =~ "Changes to be committed" ]] || [[ ${git_status} =~ "Unmerged paths" ]] ; then
        branch_colour="${RED}" 
    elif [[ ${git_status} =~ "Changes not staged for commit" ]] ; then
        branch_colour="${YELLOW}" 
    elif [[ ${git_status} =~ "Untracked files" ]] ; then
        branch_colour="${LIGHT_BLUE}" 
    else
        branch_colour="${LIGHT_GREY}"
    fi

    # The hyphen in the pattern for the branch name needs to be at the
    # beginning of the pattern so that it isn't interpreted as a range,
    # as in a-z.
    # See this for more information on the restrictions on naming git branches:
    # https://www.kernel.org/pub/software/scm/git/docs/git-check-ref-format.html
    remote_pattern="Your branch is (.*) '([a-zA-Z0-9_-]+)/([-a-zA-Z0-9_.]+)' by ([0-9]+) commit"
    if [[ ${git_status} =~ ${remote_pattern} ]] ; then
        commits="${BASH_REMATCH[4]}"
        if [[ "${BASH_REMATCH[1]}" == "ahead of" ]] ; then
            branch_status=" ${GREEN}${commits}↑"
        else
            branch_status=" ${RED}${commits}↓"
        fi
    else
        branch_status=""
    fi

    # if your local branch and the remote branch have diverged, make it red
    diverge_pattern="Your branch and '([a-zA-Z0-9_-]+)/([a-zA-Z0-9_-]+)' have diverged"
    if [[ ${git_status} =~ ${diverge_pattern} ]] ; then
        diverge_detail="and have ([0-9]+) and ([0-9]+) different commit(s)? each, respectively."
        if [[ ${git_status} =~ ${diverge_detail} ]] ; then
            local_branch="${BASH_REMATCH[1]}"
            remote_branch="${BASH_REMATCH[2]}"
        fi
        branch_colour="${RED}"
        branch_status=" ${local_branch}↕${remote_branch}"
    fi

    if [[ ! "$branch_name" ]] ; then
        branch_name='NO BRANCH'
        if [[ ! "$(git remote -v)" ]] ; then
            branch_name='NO REMOTE'
        fi
        branch_colour="${PURPLE}"
    fi

    GIT_BRANCH="${branch_colour}(${branch_name}${branch_status}${branch_colour})"
}

function set_prompt_symbol {
    if [[ $1 -eq 0 ]] ; then
        PROMPT_SYMBOL="${NONE}\$"
    else
        PROMPT_SYMBOL="${RED}[$1]\$"
    fi
}

function set_bash_prompt {
    # get return value of last command 
    set_prompt_symbol $?

    # set the TITLEBAR variable
    set_titlebar

    # set the VIRTUALENV variable
    set_virtualenv

    # set the USERNAME variable
    set_username

    # set the CWD (current working directory) variable
    set_current_working_directory

    if is_git_repository ; then
        set_git_branch
    else
        GIT_BRANCH=""
    fi

    export PS1="${TITLEBAR}${VIRTUALENV}${USERNAME}:${CWD}${GIT_BRANCH}${PROMPT_SYMBOL}${NONE} "
    export PS2="${LIGHT_BLUE}>${NONE} "
}

# An environment variable provided by bash. The contents of this variable
# are executed as a regular bash command just before bash displays a prompt.
PROMPT_COMMAND=set_bash_prompt