Why:
1. `$_` is marked as deprecated
https://fishshell.com/docs/current/language.html#envvar-_
2. `$_` contains wrong process name in cases like this one:
```fish
sleep 1000 # `sleep` is the process, now press Ctrl-Z to suspend
fg # unsuspend it, now `fg` is shown as the process
```
`status current-command` will show `sleep` instead, which makes more
sense.
A refactor changed this block from a `set git_dir $PWD` to
`set git_dir $real_pwd`, but as `real_pwd` is a "static" variable and
not dynamically computed, this breaks within the `pushd` / `popd` flow.
Instead of using `$real_pwd`, we need to compute the *current* directory
by calling `__bobthefish_pwd` again.
Fixes#249.
* Add FNM as an alternative to NVM
* Made the __bobthefish_prompt_nvm generic for nvm and fnm
* Hide errors on node_manager current
* Check for color_nvm and set color_node based on that
- Improve performance significantly in the base case (i.e. when git or something isn't slowing it down anyway).
- Make `bobthefish_display_colors` a non-underscore function. It's meant for public use :)
- Support previewing _different_ color schemes via `bobthefish_display_colors`. Pass a color scheme name, or `--all` to preview everything.
- Make color overrides a bit fishier: use a `bobthefish_colors` function to override color schemes, rather than declaring a whole pile of variables.
- Add support for a base color scheme in `bobthefish_colors`, in case you don't want to override everything.
- Add a deprecation notice with upgrade instructions for users with old-style custom color schemes.
