Note that we purport to respect the XDG base directory specification as to where configuration files are located, where data files are located, where output file caches are located. Mentions of XDG variables refer to that document.
This specification allows the user to specify some environment variables to customize how applications behave to his preferences.
On Windows platforms, when not using Cygwin,
instead of the XDG base directory specification,
we try to use folder configuration from the registry regarding
Common AppData and similar directories.
Since support for querying the Windows registry
is not possible to do in reasonable amounts of portable Common Lisp code,
ASDF 3 relies on the environment variables that Windows usually exports.