This SpaceFM petbuild was developed by Dima Krasner (dimkr) for Vanilla Dpup, but the original spacefm petbuild is now removed from Github and replaced by a petbuild for zzzfm (fork of spacefm) at the following link: 

https://github.com/vanilla-dpup/woof-CE/tree/vanilladpup-12.0.x/woof-code/rootfs-petbuilds/zzzfm

The current SpaceFM layer-shell-patch is ported from the above zzzfm link.