jsonmerge_git_merge_driver VS DMFO

I investigated the option of using a custom git merge driver for a project where we were planning to version control a bunch of data files using git.

Here's a proof of concept python merge driver I bashed together at the time to auto-merge JSON objects: https://github.com/fcostin/jsonmerge_git_merge_driver

This never went anywhere near production, but it was very easy to put together something basic.

One complication with using a custom merge driver, as discussed by https://github.com/Praqma/git-merge-driver , is that they need to be configured inside the `.git/config` of the repo, which itself is not version controlled. So there's an additional config management overhead to rolling that out to everyone in a machine. Additionally, if outsourcing hosting for git repos, it may not be supported to install and configure a custom merge driver for merges conducted by the hosting platform (e.g. merges created by github.com pull request workflow).

One idea I had at the time was using external schema files (e.g. JSON schema for JSON files) to help guide/constrain the result of the merge. I never implemented it, but it should be possible. If the schemas were also version controlled in the same git repo that stores the data, you'd need to figure out which one (and which version) to load when resolving a merge conflict of a data file. There doesn't seem to be a well-supported robust way for a merge driver script to discover the source and destination branches, but there are some potentially fragile ways of doing it that work some of the time.

I looked this up and for anyone wondering, it's called "diff/merge drivers", but there are only a handful of them out there. Some highlights from a few minutes of searching:

- MS Office: https://github.com/lcnittl/DMFO