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Comment by bj-rn | Hacker News Reader

Do you know vvvv gamma[1][2]? It's a visual programming environment for the .Net ecosystem. It's documents are saved in a XML format and they have build a visual merge / diff tool that works quite well. The strategies it applies are explained in detail in the readme of the repo[3].

[1]https://visualprogramming.net

[2]https://thegraybook.vvvv.org

[3]https://github.com/vvvv/MergeVLDocs

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This highlights the crux of the issue. The problem is not that visual programs are inherently resistant or impossible to being compared and merged. In fact, because a lot of syntactic and semantic information is built into the representation, it often becomes more clear when doing comparisons. The actual problem is that existing tooling, like Git, are myopic in that they assume all programs should have text-based representations. The problem is that the status quo does not scale to visual programs and not the other way around.

Thus, visual tooling for comparison is currently bespoke for particular environments, like that of vvvv or LabVIEW, and are usually hampered because of things like Git. There's a reason why game and art studios often use Perforce and Plastic SCM rather than Git, and it's because those studios have comparison needs that do not revolve around pure text.

Is the ability to show a non-text-based diff that related to how a source control system works under the hood though? Sure, a text-based diff tool may use some of the same underlying algorithms to determine what the differing lines are, but I wouldn't assume they have to, and usually have options to do things line ignore case/whitespace/line endings/ formatting or show mid-line (even per character) differences that go beyond how git itself calculates diffs. A top level diff-tool that can proxy out to file-format specific tools would seem to fit well enough into the git toolchain. It's having them integrated into something like bitbucket or github for PR reviews that would be truly powerful.

That's a good point. The issue may simply be one primarily of framing in that text-based diffing and merging tools were not natural, so to speak, but had to be built. And even now, they're not great. I'm constantly irritated by text-based diffing tools because they barely understand anything beyond lines of text. I'm interested to see more semantic diff and merge tools built out.

Regarding source-code control, I think it's a problem mainly of Git and not tools like Perforce or Plastic SCM which handle binary files that change over time better. It's also an issue for things like GitHub, which as far as I know, does not provide any hooks for custom diffs to be viewed in the browser.

It feels like this should be solvable though. I’m reminded of this which was posted very recently:

https://www.fast.ai/2022/08/25/jupyter-git/

Definitely solvable! People just got to work on it like they have text-based diffing tools. I'm trying to, but I am slow. For visual languages, the problem mainly lies in graph and constraint algorithms, something I'm trying to come up to speed on.

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