Replace usage of fish_user_paths with symlinks

[thernstig]

fish_user_paths has the unfortunate side effect that if it points
to a path somewhere in the user's home directory, the path will be
set to the full path (i.e. /home/username/ instead of ~/) inside
the fish_variables file.

This is unfortunate because a user that wish to share the
fish_variables file between multiple computers, to get a unified
shell setup, it's not possible since the path will point to a home
directory that might not be the same between the host (since the
user possibly has different usernames on different hosts).

This aims to rememdy this by using symlinks instead of
the fish_user_paths variable.

/fixes #93

[thernstig]

@jorgebucaran Let's see if you like this or not. The only downside I see is that I had to point out all of node, npm and npx. Your previous version was agnostic to this.

[andreiborisov]

It seems if we'd move this into nvm function itself (with appropriate configuration checking), it should also fix #101

[thernstig]

I could look into that, but @jorgebucaran has not made any comments so I am not sure if he has any intention to merge this.

[jorgebucaran]

The only downside I see is that I had to point out all of node, npm and npx. Your previous version was agnostic to this.

This seems like a significant downside. 🤔

fish_user_paths has the unfortunate side effect that if it points
to a path somewhere in the user's home directory, the path will be
set to the full path (i.e. /home/username/ instead of ~/) inside
the fish_variables file.

Maybe fish_user_paths can address this issue in a future fish distribution if we propose a change! :)

I could look into that, but @jorgebucaran has not made any comments so I am not sure if he has any intention to merge this.

Thank you, but probably not at the moment. 🙇

[thernstig]

@jorgebucaran It is possible to symlink a directory, getting rid of having to point out each individual binary. (Not that I think it is a big deal, it's not like it changes very often if at all).

I doubt they will change fish_user_paths.

What is the major reason you do not like the change. Is it that you do not like symlinks? The wording "probably not at the moment" leaves me in confusion why you wanted me to write this MR (which you asked for) and where you want it to go.