Markdown seems ubiquitous nowadays. In its raw form it is human readable, as well as being machine-parsable into HTML / PDF, etc.
Git's README is markdown (https://github.com/git/git/blob/master/README.md) but the releases notes are still plain text ( https://raw.githubusercontent.com/git/git/master/Documentation/RelNotes/2.19.0.txt). I realize those are two contradictory datapoints. Ho hum :-( - Paul
