Emily Shaffer <emilyshaffer@xxxxxxxxxx> writes: > A couple things. Firstly, a semantics change *back* to the semantics of > v3 - we map from gitdir to gitdir, *not* from common dir to common dir, > so that theoretically a submodule with multiple worktrees in multiple > superproject worktrees will be able to figure out which worktree of the > superproject it's in. (Realistically, that's not really possible right > now, but I'd like to change that soon.) Sounds sensible. > Secondly, a rewording of comments and commit messages to indicate that > this isn't a cache of some expensive operation, but rather intended to > be the source of truth for all submodules. I'd expect that there is a way (e.g. "git fsck") that helps the users notice when the actual filesystem layout contradicts with what the gitdir-to-gitdir link says, and repair the repositories when they go out of sync if possible. It would be similar to "git worktree", where a link between the ".git" file that records "gitdir:" in a secondary worktree and the repository's $GIT_DIR/worktrees/*/gitdir, and the "repair" command can be used to bring them back in sync after moving the real repository without telling the secondary worktree about the move. > I did discuss Ævar's idea of relying on in-process filesystem digging to > find the superproject's gitdir with the rest of the Google team, but in > the end decided that there are some worries about filesystem digging in > this way (namely, some ugly interactions with network drives that are > actually already an issue for Googler Linux machines). Plus, the allure > of being able to definitively know that we're a submodule is pretty > strong. The other side of the coin is that, even when a configuration variable says that you are a submodule of the superproject at location X, if such a submodule gets moved out of the superproject (perhaps because the end-user wanted to concentrate on that submodule project alone as an independent project) and the superproject that used to be at location X got archived away, trusting and relying on what the configuration variable says would not help us access the now-gone superproject. And that would not change no matter how strongly we declare that it is the source of truth. Unless we have a very good way to detect inconsistency and stop spreading the damage (e.g. the setting thought our superproject sits at directory X, but that location is now occupied by a different repository that is not related), I am still skeptical about the "setting is the sole truth" design.
