Canta is a flat Material Design theme for GTK 3, GTK 2 and Gnome-Shell which supports GTK 3 and GTK 2 based desktop environments like Gnome, Unity, Budgie, Pantheon, XFCE, Mate, etc.
Unfortunately this repo doesn't have the commit history for Materia, but one could make a diff between what is currently in this repo and Materia at the commit it was forked at, then apply that diff on top of the current Materia code, then commit THAT diff to this repo...
e.g. https://github.com/nana-4/materia-theme/commit/4e2aa1c3dc2a91de44c37d439a33a39e29fa1c4a
Unfortunately this repo doesn't have the commit history for Materia, but one could make a diff between what is currently in this repo and Materia at the commit it was forked at, then apply that diff on top of the current Materia code, then commit THAT diff to this repo...