bin/git-ps1

#!/usr/bin/env bash
r=
b=
g="$(git rev-parse --git-dir 2>/dev/null)"

if [ -n "$g" ]; then
    if [ -d "$g/../.dotest" ]
        then
        if test -f "$g/../.dotest/rebasing"
            then
            r="|REBASE"
        elif test -f "$g/../.dotest/applying"
            then
            r="|AM"
        else
            r="|AM/REBASE"
        fi
        b="$(git symbolic-ref HEAD 2>/dev/null)"
    elif [ -f "$g/.dotest-merge/interactive" ]
        then
        r="|REBASE-i"
        b="$(cat "$g/.dotest-merge/head-name")"
    elif [ -d "$g/.dotest-merge" ]
        then
        r="|REBASE-m"
        b="$(cat "$g/.dotest-merge/head-name")"
    elif [ -f "$g/MERGE_HEAD" ]
        then
        r="|MERGING"
        b="$(git symbolic-ref HEAD 2>/dev/null)"
    else
        if [ -f "$g/BISECT_LOG" ]
            then
            r="|BISECTING"
        fi
        if ! b="$(git symbolic-ref HEAD 2>/dev/null)"
            then
            if ! b="$(git describe --exact-match HEAD 2>/dev/null)"
                then
                b="$(cut -c1-7 "$g/HEAD")..."
            fi
        fi
    fi

    if [ -n "$1" ]; then
        printf "$1" "${b##refs/heads/}$r"
    else
        printf "%s" "${b##refs/heads/}$r"
    fi
else
    printf "not-in-git"
fi