nvm install can throw "Invalid redirection target"

[deleteme]

I encountered the following error when running nvm install.

~/.config/fish/functions/_nvm_index_update.fish (line 7): Invalid redirection target:
    ' >$index.temp 2>/dev/null && command mv $index.temp $index && return
      ^
in function '_nvm_index_update'
	called on line 32 of file ~/.config/fish/functions/nvm.fish
in function 'nvm' with arguments 'install'
usage: mv [-f | -i | -n] [-v] source target
       mv [-f | -i | -n] [-v] source ... directory
nvm: Invalid index or unavailable host: ""

I found these two related issues #130 and #139 but since I also experienced the error I figured I could track down some reproduction steps.

In Shell 1

1. curl -sL https://git.io/fisher | source && fisher install jorgebucaran/fisher
2. fisher install jorgebucaran/nvm.fish

In Shell 2

1. nvm
2. nvm install

The attached video demonstrates how to reproduce the bug:

nvm-error-repro-steps.mov

The error doesn't happen in new shells. When I noticed that nvm worked in a previously open shell, I assumed that nvm install would work too.

[jorgebucaran]

Fixed by making nvm_data and nvm_mirror universally scoped, so that they're immediately available to all running sessions after installing the plugin. Thank you! 💯