asdf Plugin Capitalization & Silent Failing

[ctsstc]

Describe the bug

If you add a plugin with different capitalization asdf will not function properly.
There are also no warnings for missing/mismatched plugins listed in the .tool-versions.

To Reproduce

Tell us what actions you performed before the issue occurred

Steps to reproduce the behavior:

For example if you added the following it would expect Ruby instead of ruby.

asdf plugin-add Ruby https://github.com/asdf-vm/asdf-ruby.git

If the .tool-verions has ruby instead of Ruby it will not install.
There's no warning for not having plugins added that are listed in a .tool-versions.
Also I think it should be case insensitive.

If you try to add the same plugin with different capitalization it will say it's already been added.

Expected behavior

I think it should be case insensitive when you run asdf install.

A warning would be nice if there's something listed in .tool-versions that you haven't yet added. It would be even nicer if it tried to push you in the right direction or asked you if you wanted to install the associated plugins.

Actual behavior

No error, it doesn't say anything installs if there's a capitalization mismatch.

Environment

OS:
Darwin Coders-MBP 19.6.0 Darwin Kernel Version 19.6.0: Sun Jul  5 00:43:10 PDT 2020; root:xnu-6153.141.1~9/RELEASE_X86_64 x86_64

SHELL:
zsh 5.7.1 (x86_64-apple-darwin19.0)

ASDF VERSION:
v0.8.0

ASDF ENVIRONMENT VARIABLES:
ASDF_DIR=/usr/local/opt/asdf

ASDF INSTALLED PLUGINS:
nodejs                       https://github.com/asdf-vm/asdf-nodejs.git
php                          https://github.com/asdf-community/asdf-php.git
ruby                         https://github.com/asdf-vm/asdf-ruby.git

asdf plugins affected (if relevant):

Screenshots
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Additional context
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[Stratus3D]

I don't think asdf should be case insensitive, because of the operating systems asdf runs on are case sensitive (OSX is a strange one, but generally things work better if you treat it as case sensitive).

I warning when adding a plugin with an uppercase name should be all that is needed to avoid this issue. Unless necessary I don't think plugin names should include uppercase characters.

[jthegedus]

Currently we're running a regex match over plugin names:

asdf/lib/functions/plugins.bash

Line 59 in e1fd8ad

local regex="^[[:alpha:][:digit:]_-]+$"

Requirements to close this Issue:

• on plugin add, warn if the user names a plugin with an uppercase character. Not all OSs are case sensitive. We recommend naming everything with lowercase to avoid possible issues.
• assert the warning in a test

Related PRs:

• fix: regex validate plugin names on plugin add cmd #1010
• fix: update plugin-add regex to support other languages #1241