vs: shell functions to transparently call hg or git, whichever is appropriate

vs.sh

vs() {
    # Guesses which version control system is correct for the current
    # directory, then executes it with "${@}":
    #   $ cd hg_repo/
    #   $ vs version
    #   Mercurial Distributed SCM
    #   ...
    #   $ cd ../git_repo
    #   $ vs version
    #   git version 1.8.1.1
    local vcs
    vcs="$(vsname)" || {
        echo "error: not in a VCS repository." >&2
        return 1
    }
    "$vcs" "${@}"
    return $?
}

vsname() {
    # Guesses which version control system is correct for the current
    # directory:
    #    $ cd hg_repo/
    #    $ vsname
    #    hg
    #    $ cd ../git_repo
    #    $ vsname
    #    git
    #    $ cd /tmp/
    #    $ vsname
    #    $ echo $?
    #    1
    local test_vcses=( "hg" "git" )
    local vcs=""
    local dir="$PWD"
    while [[ "$dir" > "/" ]]; do
        local test_vcs
        for test_vcs in "${test_vcses[@]}"; do
            if [[ -d "$dir/.$test_vcs" ]]; then
                vcs="$test_vcs"
                break;
            fi
        done
        dir="${dir%/*}"
    done

    if [[ -z "$vcs" ]]; then
        return 1
    fi

    echo "$vcs"
    return 0
}

for vscmd in di ci st pull push co show
do
    alias $vscmd="vs $vscmd"
done