Quotes make it only return results that contain exactly what's in the quotes. All you need to do is put a string in your website that is unique to all indexed pages. Since there's no length limit (well, google searches have a max length, but it's pretty long), I expect that the vast majority of web pages will have some phrase you can use like this.
In theory, you could just search for the entire contents of a page in quotes and it'll be the only thing that pops up unless another page is identical or contains an identical copy of the first page within it.
Simple quantum search entanglement. By observing the result, Torvald has changed the outcome.
But seriously, it's because his post gets reposted and federated across all those instances, and Google deems those more relevant than the GitHub page.