This project uses git submodules. To clone, run: git clone --recursive git://git.build2.org/build2.git Or: git clone --recursive https://git.build2.org/build2.git Alternatively, if you have already cloned without --recursive, run: git submodule update --init The checked out libbuild2/version.hxx and libbuild2/config.hxx will be overwritten during the build process but these changes should be ignored. To do this automatically, run: git update-index --assume-unchanged libbuild2/version.hxx libbuild2/config.hxx