no clue :) just to push it
[demo] / .gitmodules
1 [submodule "external/gph-math"]
2         path = external/gph-math
3         url = https://github.com/jtsiomb/gph-math.git
4 [submodule "external/libimago"]
5         path = external/libimago
6         url = https://github.com/jtsiomb/libimago.git