Sets the node version automagically when changing dirs in fish shell with nvm when .nvmrc is present or in a parent dir

use_nvmrc.fish

# use_nvmrc.fish

# TODO: save this in `$HOME/.config/fish/conf.d`  

# `nvm use` whenever .nvmrc is present in $PWD when using fish shell
# when traveling deeper, use the parent .nvmrc unless otherwise set
# also go back to default nvm when leaving the nvmrc-specified zone

function set_nvm --on-event fish_prompt
    # if the current directory hasn't changed, do nothing
    string match -q $PWD $PREV_PWD; and return 1

    # if the current directory is within the previous one where we found an nvmrc
    # and there is no subsequent .nvmrc here, do nothing, we are in the same repo
    string match -eq $PREV_PWD $PWD; and not test -e '.nvmrc'; and return 1

    # if we clear those checks, keep track of where we are
    set -g PREV_PWD $PWD

    if test -e '.nvmrc'

        # if we find .nvmrc, run nvm use
        nvm use

        # and remember that we used that node
        set NVM_DIRTY true

    else if not string match $NVM_DIRTY true

        # if we have set nvm and have stepped out of that repo
        # go back to default node, if not already on it
        not string match -eq (nvm current) (nvm alias default); and nvm use default

        # and clear the flag
        set NVM_DIRTY
    end
end

# inspired by the debate here: https://stackoverflow.com/questions/23556330/run-nvm-use-automatically-every-time-theres-a-nvmrc-file-on-the-directory/50378304#50378304