Bug: Notation panics on init when $HOME and $XDG_CONFIG_HOME unset

[JasonTheDeveloper]

What is not working as expected?

The bug relates to an issue raised in fluxcd/flux2#4961

This gist of the issue is when $HOME or $XDC_CONFIG_HOME are unset, dir/path panics when initialising

notation-go/dir/path.go

Lines 82 to 97 in 974c291

	func init() {
	loadUserPath()
	}
	// loadUserPath function defines UserConfigDir and UserLibexecDir.
	func loadUserPath() {
	// set user config
	userDir, err := userConfigDir()
	if err != nil {
	panic(err)
	}
	UserConfigDir = filepath.Join(userDir, notation)
	// set user libexec
	UserLibexecDir = UserConfigDir
	}

What did you expect to happen?

I would expect notation to not panic, breaking any application importing the notation SDK when $HOME and $XDC_CONFIG_HOME are unset.

How can we reproduce it?

Sets can be found in the reference issue

Describe your environment

OS: Arch Linux, Debian Bookworm
Golang: 1.22.5

What is the version of your notation-go Library?

v1.1.0