I do something similar with Syncthing, except I use pass and go-pass on my and my spouse's devices. Those utilities store their data in a git repo already by default, but rather than syncing those repos directly, I have set their upstream remotes to local bare repos which is what Syncthing actually syncs. This avoids contention internal to the git repos which I could see causing some problems through normal git operation and the actual sync between devices should be mostly atomic.
(go-)pass automatically does a push/pull due to several operations which keeps the password store in sync and Syncthing does its thing with the bare repos.
This has reduced my maintenance burden on my spouse's devices down to practically zero. The worst case to fix things is I need to `git pull --rebase` in the bare repo. The pass repo format uses individual encrypted files for each password entry (for better or worse) so I have yet to run into a conflict in the same entry.
Why not just push/pull git branches normally? I had previously been doing that but if you want devices to sync that may not always be online, then you must involve an always online git server (which isn't a great idea due to one of pass's weaknesses).