OmniDiff can diff: code (25 languages), config, images, PDFs, archives, cursors, fonts...
It's fast. It can diff C++ files of tens of thousands of lines in under 100ms, on a 2023 ThinkPad T14s.
It's open source. AGPLv3.
It's based on real diffs. I looked at the 7400 repositories that are listed in Gentoo packages, sampled 2000 diffs and solved them manually to get a good understanding of what is needed, before putting together the diff pipelines for each content type. Incidentally, this also forms the basis of the CI pipeline, so the robustness of the codebase is quite high.
I'm still developing it. It's v0.3.0 at this time. But I have been using it daily as my git difftool for months now, and it works well.
AI Disclosure: Yes, I do use AI. No, I do not vibecode.
Delta adds color to the standard git diff algorithm.
Omnidiff uses a completely different algorithm.
About a third of diffs are significantly better.
Git will highlight moved code and delta shows that, so how does OmniDiff differ from
git diff --color-moved=zebra --color-moved-ws=allow-indentation-changeThe default git diff uses the Myers diff algorithm as implemented in xdiff. It's a line based diff with some pre and post processing for better results.
The move detection is a post-processing step that only works on lines and additionally only works if you also enable coloured output.
It can't match "moved-but-eddited" code and it can't match "this one log line was copied 3 times in the new code" or the refactoring equivalent "these 2 blocks of code were merged into one reusable function".
You have to use more syntax-aware algorithms to get true move detection. OmniDiff matches the nodes of the AST to get some of that syntax awareness.
In the meantime, I added support for all other non-code file formats. Hence the name change.
It’s quite a big chunk of functionality.
IMO, you should seek to make this a standard that wins, and hopefully other opportunities that come will be where you make commercial hay. My unsolicited 2c.
I actually don’t care about the commercial license. It’s more of an experiment for my own amusement than an actual attempt at building a commercial project.
If it inspires someone to build another one and we still end up with a better differ, I’m ok with that world. As long as the open source community has a better differ.
Note that there already are at least 3 that I am aware of. But they do perform worse on speed and accuracy.
This is not to say you can't or shouldn't use AI, but it's important to understand the tradeoffs you're making.
[1] https://www.scotusblog.com/cases/thaler-v-perlmutter/ [2] https://www.jenner.com/en/news-insights/client-alerts/us-cop...
That said, even under those rules, I would be comfortable arguing before the court that this code has significant human involvement and easily passes the copyright standard.
It’s also why I don’t think someone can just easily create another one and license it under BSD. My code is AI assisted, but all truly important pieces were human made.
Get one AI to describe what the code does, and another to implement based on that description. You might even get away with a human doing one of the steps. A variation of the classic “clean room reverse engineering” method that was used by Compaq to reimplement IBM's BIOS and start the clone PC market.
Some argue that “it doesn't work like that” but it certainly seems to be what some people are doing and as yet no one has been confident enough that their copyright extends through this mechanism that they've tested the theory in court.
Note: I'm not saying it is right, but that it might well be perfectly legal. It is definitely possible, practical even. I'd still release stuff under AGPL/similar for the same reasons stated above, but I'd not operate under any illusion that I'd be safe from someone using that method to copy everything they wanted to.
But I am counting on the fact that _companies_ would be too worried about legal uncertainty to try this.
Oh, my sweet summery child :-)
Companies have been doing far more dodgy things, things that look objectively illegal where-as the clean-room reverse engineering thing looks to me (caveat: not a legal expert at all) to be legally defensible, for a long time, definitely pre-AI.
Even if a company operating in your jurisdiction, where you as an individual might have a cat in hell's chance of even trying to sort the situation to your preference, might not, you can bet your last <currency unit> that a company elsewhere will feel more free to do so if they wanted what you have without agreeing to your terms.
If it’s a small company, it’s not worth it, but then again they are not causing a lot of damage either. If it’s a big company, they will find me unexpectedly resistant to usual legal bullying tactics. I have legal insurance, multiple lawyers as friends and don’t have a job so have loads of time for filing paperwork.
Though AI code copyright is an unknown pretty widely either way, it's too new for the legal system to have caught up with it yet.
… we don’t know what to do with AI copyright either. I assume a referendum will sort it out at some point.
Diffsitter and Difftastic have been around for a while, both MIT, so I doubt it.
Difftastic only diffs code, which is only 2/3 of all diffs.
When only measured on stuff difftastic supports:
Difftastic is perfect on 64% of diffs and near-perfect on 17% more.
Omnidiff is perfect on 90% of diffs and near-perfect on 5% more.
Speed is
p50 - 35ms difftastic vs 4ms OmniDiff p99 - 637ms vs 420ms
Difftastic wins on license. MIT vs AGPL.
I'm a little confused on that, since in other comments you've mentioned that AGPL was a deliberate choice for <reasons>. So, what's the definitions of "winning" here?
But it was worth pointing out the difference in license, it is one of the ways in which the projects differ.
Discrete users would arguably win more with integrity of AGPL, but developers have reasons to prefer MIT.
Hi! as a developer, I personally prefer it when the libraries/tools used in my projects are GPL or another Copyleft license. The drove of MIT projects from the past decade has been depressing.
One feature I miss from difftastic is showing diffs side-by-side on wide terminals, and unified when narrow.
You can force it with “v”.
I am not super set on that value, if the community has a better default for “wide”, happy to modify it.
I feel like since terminal widths "classically" (when dinosaurs like me originally started coding) topped out at 79/80 columns wide, and thus why many code "style guides" still to this day suggest a code line-length of around 80-ish (to ensure that code lines "fit" on any terminal), I'd say maybe double-ish that might count as a good "wide" value? Say 160-ish? Meet or exceed that width to be considered "wide" by default?
Also, maybe a command-line switch, env variable, and/or config value to set it manually to some other user-preferred default value? Then I could set some arbitrary width like 128 or 256 if I like powers of two or somesuch silliness? :)
There's a screenshot and video of it here that I wrote a while back: https://nickjanetakis.com/blog/awesome-git-diffs-with-delta-...
In OmniDiff's readme and web version I didn't see a way to do that.
In a different comment you mentioned OmniDiff is much better than Delta and you mentioned "About a third of diffs are significantly better.". Can you provide some examples of these? I've never seen Delta fail a diff.
Also Delta has a package for Arch in its official repos. For folks who just want a "it works" experience, that's a pretty big win. With Delta the same package can be installed in the same way on Debian, Arch and macOS with Brew using standard package managers. With OmniDiff, there's 3 different ways to install it (manual deb package on Debian, manual package compile on Arch and brew install on a Mac). Just something to think about, as someone who has public dotfiles that work in those 3 environments, I'd skip OmniDiff based on this alone.
As for packaging. Unfortunately AUR is closed at the moment due to spam. I can add brew commands for Linux, happily.
In terms of “better”. It’s actually somewhat complex, but a simple way to think about it is that if you move a function up or down in the same class, text-based diffs paint that as “Deleted here, Inserted there” where ideally you would want it to say “Moved”.
Since most people do click-and-run most of the time (based on decades long research, n=1), I'll just add paste the link for more examples: https://ivankovic.github.io/omnidiff/showcase/content.html
Any interest in getting the setup upstreamed[1] so that users only need to `git config --global diff.tool omnidiff` to enable it by default? Disclosure: I created `git difftool` a long time ago, and am always happy when builtin support for useful tools are added to it. Feel free to reach out if you'd like help making that happen.
It’s a long term goal to solve, but it’s the hardest one.
I’ll definitely reach out to you to upstream. Thank you for the kind offer!
In practice, tree hashing is doing a huge amount of work because most diffs are tiny. Half of all diffs are less than 10 lines, so a hash can extremely quickly match large subtrees.
In a profoundly degenerate case of a C++ header file with only a 20MB array of bytes, it detects a degenerate tree and uses Myers O(N) sequence diffing algorithm instead of treating it as a tree.
I actually don’t know how to do that and stay under a bounded edit distance.
Alternatively, you can crash it if you just encode the entire “Star Trek - In the pale moonlight” episode as a sequence of bytes in a const int array in C++.
I’m sure there’s an interesting result there, but I am not the person to find it :D
Good episode btw
I actually do TWO solutions for each test case: a minimal diff and a maximal diff. Pressing 'm' in the TUI pops up a settings page where you can choose how the diff works.
I am actively researching how many ways there are to "paint" the same diff and user preferences and non-uniqueness of diffs is something I am super interested in.
If you would like to, it would be super useful for me to know what diff you don't like and why. It would help make the diff better for users with different visual preferences.
I feel like the moved code cases would look great in https://github.com/andunieee/twain, I was looking into how I could slurp your code and make it work there (although for some reason I have the impression that I had already seen this repository in the past, I can't remember where).
If I understand your goal correctly, you are looking to especially focus on the visual part of the diff and provide a nice UI for it, and you would like to use OmniDiff as a library?
If so, then let's talk. I have been delaying the design of the API because nobody has a use for it yet, so it is mostly driven by the needs of the CLI/TUI at the moment.
Ping me on my email if you want.
I feel safer, as a user, enjoying the freedoms that the AGPL provides me. (No evil middleman will be able to give me non-free versions of this program.)
AGPL totally allows commercial use. You just have to give back.
You can do this with delta: `git diff | delta --side-by-side`
OmniDiff also works directly with git diff and git log -p, through GIT_EXTERNAL_DIFF. This path needs no difftool config:
GIT_EXTERNAL_DIFF=omnidiff git diff(If commit A adds a line to the end of a bullet list in markdown and commit B does the same, they will conflict even though resolution is trivial for a human)
I’m not sure if I’m understanding this correctly : so for the remaining 0.05% of code changes, this tool would just… miss it? That seems horrible for a diff tool :O
But so will every other tool, because it is things like a C++ header file with 128MB of PNG data hardcoded as an array.
Editors don’t even open those files.
But then I would rephrase that because it's confusing, and not doing justice to your tool.
Thanks!
The problem is the degenerative syntax tree that TreeSitter produces in case of, for example a multi-million array of bytes. This causes a stack overflow in the TreeSitter C code which takes down the Rust process with it.
The correct solution would be to prevent TS from crashing, or isolate the C<->Rust boundary better.
Or just, not support that for v0.3. Because if you are diffing the collected works of Shakespeare as a binary blob in a C++ header, maybe diffing isn't your biggest problem.
vi opens multi-GB files just fine.
And for multi-TB files, "less -n" works.
You need to broaden your horizons about editors. Not all of then are javascript-based slopfests
Additionally, here's an appropriate XKCD: https://xkcd.com/378/
Difftastic only diffs code, which is only 2/3 of all diffs.
When only measured on stuff difftastic supports:
Difftastic is perfect on 64% of diffs and near-perfect on 17% more.
Omnidiff is perfect on 90% of diffs and near-perfect on 5% more.
Speed is
p50 - 35ms difftastic vs 4ms OmniDiff p99 - 637ms vs 420ms
Difftastic is MIT vs AGPL.
Care to elaborate? What does Omnidiff offer for non-code files?
Note that you do need a terminal with image support, like kitty, alacritty.
If you do not have image support, it does its best with image2ascii, but it is obviously severely limited.
> Omnidiff is perfect on 90% of diffs and near-perfect on 5% more.
I did not find examples in the repo or any way to test what "perfect" or "near perfect" in those cases mean. On the playground you compare against unix diff only. Based on my quick comparisons with difft, I do not see much difference. Could you add a link to comparisons or show how it differs and what are those numbers based on??? I'm not dismissive, just looking for a proof or showcase.
Fair warning: the true comparison is fairly complex and doesn’t really lend itself to “quick comparison”.
Also, the research is NOT complete.
Press ? for the help menu.
Also it would be nice to have a more thorough and comprehensive comparison against difftastic, because I don't think there are much, or even any difference to code diffing compared to it: https://ivankovic.github.io/omnidiff/showcase/
Does yours support move + change detection across different files, like A/before.rs => B/after.rs (~some changes)?
An extremely thorough comparison against difftastic is in the research/ directory. I don't recommend reading it, unless you are really into diffs. Even describing the dataset takes a good half an hour.
Multi-file support is on the roadmap. Subscribe here: https://github.com/ivankovic/omnidiff/issues/63
It will diff OpenOffice compatible files.