grit

> Maybe the takeaway is that 20% is about all the LLM can muster At this point there's a long list of projects that have used LLMs to rewrite a system in Rust including: - Bun (https://github.com/oven-sh/bun/pull/30412) - Valkey (https://github.com/ianm199/valdr) - Git (https://github.com/gitbutlerapp/grit) - Postgres (https://github.com/malisper/pgrust) With the exception of Bun, these projects were done pre-fable too, so I bet Fable will make these types of rewrites even easier.

I would say it's worse, the whole C Git source code is checked in https://github.com/gitbutlerapp/grit/tree/main/git

As mentioned in another comment, it's even more clear cut in this case. They actually put the original git sources in their project repo and instructed the agent to use it as the "source of truth". Simple thought experiment. If you handed this same agents.md file (https://github.com/gitbutlerapp/grit/blob/main/AGENTS.md#sou...) to a human software developer and let them work on exactly the same goal, would their output be considered a derivative work?

The agents.md says “here’s the git source code” https://github.com/gitbutlerapp/grit/blob/main/AGENTS.md#sou... This isn’t even a question of training data, thy fed the full git source code directly to the llm.

Looking at just the `grit` executable, 58 of the top 200 largest file->resulting code sources are from clap-rs' derive functionality i.e. it's the command-line parsing. The #1 largest is, surprisingly, merge_trees[1] which comes in at 183kiB final binary size. There isn't so much code in that file that it seems reasonable, so it's potentially one of the derives in use (Debug being a common culprit for bloat) that's blowing it out. After those outliers it starts to level out quickly. Splitting it by crate: `grit` is 13.6MiB, `grit_lib` is 4.8MiB and then it's `std`, `rustls` and `regex_automata` that are the next largest. So as pure library you could hopefully shave off quite a bit of that 25MiB. [1] https://github.com/gitbutlerapp/grit/blob/main/grit-lib/src/...

This is simply plagiarism of GPL-licensed code, and license-washing as well. I can understand working backwards from a test suite, but this literally just reads the original source: https://github.com/gitbutlerapp/grit/blob/main/AGENTS.md#sou... LLM users seem to live in another world where stealing everything that isn't bolted down, and passing it off as their own work, is acceptable.

It's actually murkier than I suggest here. https://github.com/gitbutlerapp/grit/blob/main/AGENTS.md#sou...

> That's not actually the case at hand here - the agents were given the original source to reference: https://github.com/gitbutlerapp/grit/blob/main/AGENTS.md#sou... yeah fair - the "The canonical Git source code we're targeting to replicate the functionality of is in the git/ subdirectory." part makes this hard to argue against. > To the extent the resulting work is a derivative of the test suite it is possibly infringing It's this bit that I have a problem with. If I run the test, it fails and reports a failure. Now I write code and run the test again. What is the theory there that code that I wrote infringes. Simplify this down: Assume the following is copyrighted: fn test_sum() { assert_eq!(sum(1, 1), 2); } Does writing the following code: fn sum(a: u8, b: u8) { a + b } infringe on the test copyright?

> using the git test suite That's not actually the case at hand here - the agents were given the original source to reference: https://github.com/gitbutlerapp/grit/blob/main/AGENTS.md#sou... But for the sake of argument: The test suite itself is copyrighted. To the extent the resulting work is a derivative of the test suite it is possibly infringing. For example you might example that the agent would derive variable names, function names, structure sequence and organization of the code from the test suite. It might even copy comments wholesale. Those are copyrightable things. (Which is of course just the first step in analyzing if it is infringement, there would be interesting fair use, de-minimis copying, etc arguments following a conclusion that any of those were copyrighted. A product produced this way definitely could be infringing g