The first one I more or less randomly clicked on was of course »Verordnung über Qualitätsnormen für Bananen (QNormBanV)« [1], quality standards for bananas.
Is this account actually maintained by Bundestag (or other actual piece of state administration), or is it just a mirror? Also, either German law is really mature and stable, or this repository is unmaintained: last commit oin master is Jan 2013.
I'd love to see such a repository for the acts in my country, by the way, but the official source is a PDF, and most of the published acts are actually patches to existing (already heavily "patched"), like "In the section II, item 13a, change words 'foo and bar' to 'foo, baz and quux'". This mess untangled into an actual, highlighted, unified text is an actual product, and lawyers happily pay the subscription. I imagine it is similar in other countries.
I'm the original creator of that repo. Keeping it up to date is unfortunately a time-consuming manual effort. Doing version control downstream is generally a nightmare because unraveling different law changes/typo fixes is complicated (yes, lot's of typos when humans consolidate laws by hand).
It's a financially independent (it has a "pro" version) non-profit owned by the department of justice and the faculty of law of the University of Oslo. It is an official source and as such laws published there are officially, legally published and it has been that way since 2001. Laws relevant to private citizens are available for free. It's pretty neat.
Edit: oops! I replied after reading the content in an 8 hours old tab, not noticing that the repo author had already explained it in a sibling post to this one.
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From their README, it's just someone that converted the XML version published by the "Bundesministerium der Justiz und für Verbraucherschutz" (Ministry of Justice and for Customer Protection) which as they note is available at http://www.gesetze-im-internet.de/
About the Markdown version in GitHub: after a quick inspection, most diffs seem to be plain additions of content, presumably as it was converted to Markdown.
However, some diffs might have tracked changes in the laws, as this one: https://github.com/bundestag/gesetze/commit/3c1bada22f08b4e0...
I suspect the author ran the converter a few times and then abandoned it. In principle, it should be possible to keep updating it.
The improvement over the official XML version seems to be that with Markdown it's easier to get understandable diffs.
I'm not sure how they do it, but I guess that it wouldn't be extremely hard to have a small grammar to automatically convert the legalese patch into an actual git patch (most of the time, the sentences which wrap the editions are the sames).
If you have a text version, at least preprocessing and proposing changes could be doable (especially that as far as I know, formal French is quite uniform - but then, it's what I heard from others, all French I actually know comes from a Dexter's Laboratory episode). In Poland, though, the original acts are published as PDFs, and the text extraction itself needs assistance, if it's even possible without OCR: the international agreements that are side-by-side in multiple languages (Polish, other party, sometimes also English) are usually image scans saved as PDFs.
I do especially like the GitHub avatar: https://avatars1.githubusercontent.com/u/1994383 ;)