I don't think that's the case in Italy. A bill often takes the takes the form of sequences such as "in the bill n. 1234/05 at the subparagraph 2, the word X is replaced with the word Y." There isn't, to my knowledge, a notion of "document" which the patch is applied to. You can, of course, derive the documents from the successive patches, and laws on new matters contain an entire document as a "first commit". But in software engineering it's the documents/ files you care about, patches and commits only exist as a support for change management.
This seems like it should be done by some government department, but if it's not, still a lucrative opportunity for the private sector (surely every lawyer would buy a copy /subscribe to your service).
My understanding is that there are always administrative departments responsible for updating and publishing the statutes based on the bills that have been passed. This is effectively applying a patch approved by the legislative process to the repository of statutes.
If you try to dig into a mainstream news story about legislative actions to the actual bill text you'll quickly find that for all but the simplest actions the bill text is useless for understanding the effect of the bill. The problem is that you need the surrounding context of the statute or regulation that is being amended in order to understand. At least for my state and the US federal legislative systems, the web based UI for understanding all this is abysmal.
The cynic in me thinks that legislators don't even understand the true nature of their own legislation. They are making voting decisions based on staff summaries, verbal discussions, media reports, constituent sentiment analysis, etc.