No, no, no. They just suck. It's not that the concept is bad - it is in fact very good, for the exact reason you suggest. They are just abysmally badly impleme

No, no, no. They just suck. It's not that the concept is bad - it is in fact very good, for the exact reason you suggest. They are just abysmally badly implemented. They barely work at all and frequently get your repo into nonsensical states for NO REASON other than that the tooling is utterly worthless. Mercurial has subrepos that offer conceptually the exact same functionality, but is actually implemented in a way that works WITH you rather than against you, and that will not constantly break. Git submodules are just a completely unfinished feature that is nearly unusable.