While I'm also eagerly looking for an alternative to Git submodules (an initial pit of failure is that clones and checkouts aren't recursive by default, and in the long run it's annoying that branching/forking a module doesn't fork its submodules' upstreams), and the existing alternatives are poor (subtrees fail to resolve merge conflicts, and subrepos are unmaintained, fragile, and break when you rebase a clone/pull commit), I'm instantly put off by the slick commercialized sales-funnel design of your website.

I know submodules, and I sort of know subtrees (which as I understand are similar to what this tool does, except more manual and error-prone), but what are subrepos? [this]( https://www.mankier.com/1/git-subrepo)?

https://github.com/ingydotnet/git-subrepo

git subrepos work simply by copying your dependency to a subdirectory and committing the changes using one large commit that retains metadata about the update to the subrepo. For that reason, git subrepos aren't symlinks. You don't need to git clone --recursive like with git submodules, and you don't need cross-repo authentication. Updating a subrepo means performing another commit.

Even though git subrepos are the most poorly maintained, the design is simpler.

I wish someone would fork and take over maintenance.

git subrepos are the best.