nixos bash functions

function nixos-cleanup-safe () {
    df -h /
    nix-collect-garbage
    df -h /
    sudo nix-store --optimise
    df -h /
}

function nixos-garbage-add-root () {
    sudo ln -s $1 /nix/var/nix/gcroots/
}

# Update ~/nixpkgs git repository based on what is the latest nixos unstable:
# - the git 'basesystem' branch is the branch always pointing to nixos unstable
# - the git 'system' branch is based on 'basesystem' and adds my own stuff on top
function nixos-update () {
    sudo nix-channel --update 1>/dev/null 2>&1
    newref=$(cut -d'.' -f2 /nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/svn-revision)
    cd ~/nixpkgs
    oldref=$(git rev-parse --verify refs/heads/basesystem)
    [[ "$oldref" = "$newref"* ]]
    samep=$?
    currentbranch=$(git symbolic-ref --short HEAD 2>/dev/null)
    echo Current unstable branch is at: $newref
    echo Old stable branch was at: $oldref
    if [[ $samep != 0 ]]; then
        # there is an update
        echo There is a difference
        echo updating ~/nixpkgs basesystem revision
        git fetch --all --quiet
        git update-ref refs/heads/basesystem $newref
        echo updating ~/nixpkgs system revision
        git-dirty-p && echo "Dirty current working directory, quitting" && return 0
        currentbranch=$(git symbolic-ref --short HEAD 2>/dev/null)
        [[ $currentbranch != "system" ]] && echo "Not in 'system' branch, quitting" && return 0
        git rebase basesystem
    else
        echo There are no difference
    fi
}

function nixos-build () {
    sudo nixos-rebuild build -I nixpkgs=/home/cassou/nixpkgs -I nixos=/home/cassou/nixpkgs/nixos
}

function nixos-switch () {
    sudo nixos-rebuild switch -I nixpkgs=/home/cassou/nixpkgs -I nixos=/home/cassou/nixpkgs/nixos
}

function git-dirty-p {
    [[ $(git diff --shortstat 2> /dev/null | tail -n1) != "" ]]
    return $?
}