How to reference Source Code I'm writing a paper on a technique which I have implemented in open source software. I'd like to reference the location of the open source software and the code I implemented for the technique so as to increase reproducibility of my findings.

I was thinking of adding a sentence somewhere along the lines of "Note that the source code can be found at github.com/..." or "Note that the implementation is open source.\ref{myrepository}"
Which format is best?

I don't know where to put this line. In the introduction, the method description or the algorithm section? Other options would be the conclusion or the acknowledgements.
Put the link where your readers will find it most easily, i.e. as early in the document as possible. A link to your repository in the introduction would be ideal. Placing an identical reference elsewhere in your paper wouldn't hurt - nothing is worse than having to hunt through a paper just to find the single github link.

Similarly, the exact format should be conducive to finding your code, so a direct link is likely easier to follow. A formal reference may work better if you reference the repository several times within the manuscript.