Log Message:
Update to 0.12.0. From the changelog:

Breaking changes:

* Remove files containing only `asdf` wrapper functions
* align Fish entrypoint behaviour with other shells
* do not remove items from PATH in POSIX entrypoint
* rework POSIX entrypoint for greater shell support

Features:

* Support configurable `ASDF_CONCURRENCY`
* Support PowerShell Core

Documentation:

* Add Nushell installation instructions for all languages
* fix `ASDF_${LANG}_VERSION` usage
* fix Nushell-Homebrew setup instructions
* fix uninstall instructions for Fish Shell
* Improve wording of env vars section
* verbose plugin create command details

Patches:

* `asdf info` show BASH_VERSION & all asdf envs
* align Fish entrypoint behaviour with other shells
* assign default values to all internal variables
* Better handling with paths that include spaces
* create install directory with `mkdir -p`
* do not remove items from PATH in POSIX entrypoint
* enforce consistent shell redirection format
* improve readability of the non-set `nullglob` guard
* Introduce `ASDF_FORCE_PREPEND` variable on POSIX entrypoint
* lint & style errors in `bin/asdf`
* Nushell plugin list --urls
* nushell plugin list all
* Remove files containing only `asdf` wrapper functions
* remove leading asterick in Fish completion
* rename internal function `asdf_tool_versions_filename`
* rename internal plugin repository functions
* rework POSIX entrypoint for greater shell support
* support `asdf shim-versions` completions in fish & bash
* Typo in POSIX entrypoint
* warn if `.tool-versions` or asdfrc contains carriage returns