When a module is currently installed as bytecode, but without
corresponding source and without a "info.rkt" specification that
bytecode should be preserved without source, then `raco pkg` should
not count that module bytecode as a conflict (since `raco setup`
will remove it).
Packages that are installed as other than a link are not meant to be
edited, but work can get lost if a package is edited and then removed
or updated. Avoid that work loss by moving removed or updated packages
to a trash folder.
By default, the trash folder holds up to 512 packages for up to 48
hours. To disable the trash folder (for a given scope), use
raco pkg config --set max-trash-packages 0
(I expect that some variant of Greenspun's rule predicted the eventual
inclusion of "backup" management in the package system.)
