It's an incredibly hard problem though, both from a computational complexity point of view, and trying to build a comprehensible UI once you've done the structural AST diff.
I’m surprised at the lack of hyper-specific language version control tools. I thought about making a side project for one in Julia a while back but not quite sure how it would look. Some random thoughts:
- info on type, name, constant changes
- let me checkout older revisions of individual functions / objects / whatever
- on unit test result changes for functions that have unit tests
- when changes are simply a refactor and are functionally the same
Difftastic, Meld, diff -u, Word and other tools are amazing because they are usefull in many scenarios. Getting the UI right has been a long process, beingable to grok the changes is still hard even with thw best tooling. It is also a question of tool adoption it takes a long time to understand how a tool works.
Building a hyper-focussed tool won't be very useful, expect to at least rudimentarily support other file types.
How well do existing VCSs integrate with it? Did you feel restricted at any point by writing a diffing tool, instead of basing a new VCS around this concept? Do you think a deeper integration would allow supporting other functionality beyond diffing, like automatic merging, conflict resolution, etc.?
I agree that it's a very difficult problem. But as an industry, we have more than enough smart people and resources to work on it, which if solved would greatly improve our collective QoL. I can't imagine the amount of time and effort we've wasted fighting with version control tools over the years, and a tool that solved these issues in a smarter way would make our lives much easier.
The last example also add a new feature, and option for a developer to add a comment on an automated refactor.
Ordinary commits could exist on top of this as milestones.
I wouldn't be totally surprised if sooner or later Jetbrains does this. They are creating their own, often better versions of everything I feel and version control could be an obvious next step.
As someone who often prefers other solutions to theirs, I'd prefer if someone else does it first so I end up with something I can use across NetBeans, VS Code, eclipse etc and not something like Kotlin which forces me to use IntelliJ. (Don't get me wrong, IntelliJ is great, I just have NetBeans as my personal favorite.)
Git supports external diffing tools really well with GIT_EXTERNAL_DIFF, which you can use with difftastic[1]. Other VCSs are less flexible. For example, I haven't found a nice way of getting a pager when using difftastic with mercurial.
> Did you feel restricted at any point by writing a diffing tool, instead of basing a new VCS around this concept?
Oh, that's an interesting question! Difftastic has been a really big project[2] despite its limited scope and I'm less interested in VCS implementation.
I think text works well as the backing store for a VCS. There are a few systems that have structured backends (e.g. monticello for smalltalk), but they're more constrained. You can only store structured content (e.g. monticello requires smalltalk code) and it must be well-formed (your VCS must understand any future syntax you use).
Unison[3] is a really interesting project in this space, it stores code by hash in a sqlite backend. This makes some code changes trivial, such as renames.
From the perspective of a text diff, an AST diff is lossy. If you add an extra blank line between two unchanged functions, difftastic ignores it. That's great for understanding changes, but not for storage.
[1]: https://difftastic.wilfred.me.uk/git.html
[2]: https://www.wilfred.me.uk/blog/2022/09/06/difftastic-the-fan...
I already use delta[1] as a diff viewer, but I suppose GIT_EXTERNAL_DIFF is a deeper integration than just a pager. I've been aware of your project for some time now, but haven't played around with it since I wasn't sure if it would help with automatic conflict resolution, and other issues Git often struggles with. But I'll give it a try soon, thanks again.
I wasn't familiar with Unison. It looks interesting. We definitely need more novel approaches to programming, especially since our field will radically change in a few years as AI becomes more capable.
It works well, and the only time I switch back is when comparing long strings.