feat: add bash plugin

[xaf]

Summary

Description:

• Tool repo URL: https://www.gnu.org/software/bash/
• Plugin repo URL: https://github.com/XaF/asdf-bash

Checklist

• Format with scripts/format.bash
• Test locally with scripts/test_plugin.bash --file plugins/<your_new_plugin_name>
• Your plugin CI tests are green
  • Tip: use the plugin_test action from asdf-actions in your plugin CI

[xaf]

So... this might not work with asdf shims, since it creates a dependency loop.
Would require asdf to avoid using /usr/bin/env bash in the shim (at least the shim for bash) but use the system version instead.

[hyperupcall]

Yeah, some code on the asdf-side might need to be modified for this to work. Changing the shebang, or something like this are possible fixes.

[xaf]

Yeah, might make a PR for asdf to add a new binary file to use as custom shebang, which can specifically look for bash in the PATH after removing asdf. That would make asdf less dependent on bash from the env itself, while at the same time following the env, which would be a good thing!

[jthegedus]

Ping me when ready to merge (when it is adequately supportable).