GeneratePlugin copies in the specified plugin fixture into a test directory and initializes a Git repo for it so it can be installed by asdf.

GeneratePluginIndex generates a mock plugin index Git repo inside the given directory.

InstallPlugin copies in the specified plugin fixture into the asdfDataDir's plugin directory and initializes a Git repo for it so asdf treats it as installed.

InstallPluginIndex generates and installs a plugin index Git repo inside of the provided asdf data directory.

Setup copies all files into place and initializes all repos for any Go test that needs either plugin repos or the plugin index repo.

WritePluginCallback is for creating new plugin callbacks on the fly.