fix(fish): use builtin realpath over system one

[MageJohn]

Summary

Fixes the issue raised in a PR comment here: #1583 (comment)

Fish treats their realpath builtin as a fallback in case a system version doesn't exist. Not all versions of realpath support the --no-symlinks flag, which asdf.fish uses. This PR ensures that the builtin version of realpath is always used.

Other Information

Just as a note for posterity, the --no-symlinks flag for the builtin realpath was added in fish 3.2.0, released in March 1, 2021. 2 years old is good, but some slower Linux distros may lack support. If that proves to be a problem, then perhaps a different solution can be found. I think long term though the builtin will offer the best support across different systems.

[cr0t]

These changes also resolve the issue on macOS because system realpath doesn't support the given options.

I just updated to the latest asdf version 0.13.0 and started to get this error at the beginning of my sessions:

realpath: illegal option -- -
usage: realpath [-q] [path ...]
Welcome to fish, the friendly interactive shell
Type help for instructions on how to use fish
> ~

@MageJohn's patch fixes the problem.

[jthegedus]

Great contribution, thanks!

[jthegedus]

You can use this change by pulling the latest code with asdf update --head

[sample-usr]

Any idea when will this be released? asdf update --head doesn't work if installed via brew.

[kblcuk]

@rebebop at least according to github releases, 0.13.1 was release 4 minutes ago, so give it some time :)
https://github.com/asdf-vm/asdf/releases/tag/v0.13.1

[cr0t]

@rebebop if you're rushing, you can edit the asdf.fish file manually, it's here: /usr/local/opt/asdf/libexec/asdf.fish (at least on my machine).

Just add builtin on the 2nd line to get this:

if test -z $ASDF_DIR
    set ASDF_DIR (builtin realpath --no-symlinks (dirname (status filename)))
end
# ...

[sample-usr]

@rebebop at least according to github releases, 0.13.1 was release 4 minutes ago, so give it some time :) v0.13.1 (release)

@kblcuk All good :), when I posted, which was an hour ago, it was obviously not released so was only wondering.
@cr0t Thanks for the snippet