Show the current Git or Mercurial branch in your Bash prompt

branch_prompt.sh

## Print nickname for git/hg/bzr/svn version control in CWD
## Optional $1 of format string for printf, default "(%s) "
function be_get_branch {
    local dir="$PWD"
    local vcs
    local nick
    
    while [[ "$dir" != "/" ]]; do
        for vcs in git hg svn bzr; do
            if [[ -d "$dir/.$vcs" ]] && hash "$vcs" &>/dev/null; then
                case "$vcs" in
                    git) __git_ps1 "${1:-(%s) }"; return;;
                    hg) nick=$(hg branch 2>/dev/null);;
                    svn) nick=$(svn info 2>/dev/null\
                        | grep -e '^Repository Root:'\
                        | sed -e 's#.*/##');;
                    bzr)
                        local conf="${dir}/.bzr/branch/branch.conf" # normal branch
                        [[ -f "$conf" ]] && nick=$(grep -E '^nickname =' "$conf" | cut -d' ' -f 3)
                        conf="${dir}/.bzr/branch/location" # colo/lightweight branch
                        [[ -z "$nick" ]] && [[ -f "$conf" ]] && nick="$(basename "$(< $conf)")"
                        [[ -z "$nick" ]] && nick="$(basename "$(readlink -f "$dir")")";;
                esac
                [[ -n "$nick" ]] && printf "${1:-(%s) }" "$vcs"-"$nick"  #show version control app and branch
                return 0
            fi
        done
        dir="$(dirname "$dir")"
    done
}

## Add branch to PS1 (based on $PS1 or $1), formatted as $2
export GIT_PS1_SHOWDIRTYSTATE=yes
export PS1="\$(be_get_branch "$2")${PS1}";

# Faster (1ms vs 5ms) than /usr/bin/dirname
function dirname() {
    local dir="${1%${1##*/}}"
    "${dir:=./}" != "/" && dir="${dir%?}"
    echo "$dir"
}