Out of curiosity, are there any VCSs that operate on AST instead of plaintext lines? (Or is something like this being developed or proven impossible?)

I guess it should be possible to cooperate on shared codebase without need for every contributor to check in and out text files following exactly the same formatting. Or even naming convention. Or even same language, provided all collaborators can transpile to and from some agreed-upon shared AST target.

I know it might seem unhinged at first, but think about it: your (parseable) code is representation of the tree anyways (with some unrelated "whitespace fluff" around). If you follow strict formatting rules that you can express programmatically, you can recostruct that "fluff" from bare AST. If you can store all your violations against your style near the code, you can even sin and break it. If you store data about what you need to see differently from the shared AST - local renames of variables, for example - then you should be able to use your own naming convention, formatting and even source language, without bothering collaborators with tabs/spaces, hungarian notation or the fact that you prefer some different dialect or metalanguage.