It might solve it for git, but this looks like something the Review Board team came up with, and they have to integrate with many other version control systems like SVN, CVS, Perforce..etc. Seems like this is meant to address supporting many different version control systems with a single format.
I've worked at a place that used Review Board, and SVN as their primary vcs, but many devs used a local git-svn mirror for their work. Sometimes this caused problems with uploading diffs, especially if svn and git-svn were being mixed in one review. Having the Review Board cli generate a common diff format for both would have helped with that.
Exactly that. They all do things so differently that you end up creating and maintaining a separate parser for every SCM's diff format, and sometimes doing a lot of normalization of content or modification to include information the format lacks that's needed to apply the patches. And those are just for the ones that actually have a diff format -- many don't.
We needed something for ourselves at the very least. Much of DiffX came from thinking about these pain points and from talking to other SCM vendors whose engineers have also given some thought to these problems.
> Seems like this is meant to address supporting many different version control systems with a single format.
I'm sorry, this is simply wrong at so many levels. You're lauding this as a solution in search for a problem. As OP pointed out, this is already a solved problem as proven by Git. Git is not using a proprietary format. The problem of "integrate with many other version control systems" depends on whether those version control systems want to work on adding support for this feature. I guarantee you there isn't a single SVN or Mercurial maintainer complaining that they would love to share patches with Git but they are blocked because they cannot implement, let alone design, a format to exchange patches. That is not the hard part. That doesn't even register as a concern.