There should be (or is there already?) a script that automatically downloads an issue and its conversation in text or JSON format and commits it so the data/archive is in the git repo.
The script works on any git repo. It's just that the graphs being produced are similar to those found on Github. Aside from that, the script is not related to Github at all.
I would recommend my small library Color::ANSI::Util (https://metacpan.org/module/Color::ANSI::Util ) which has ansifg($rgb) and ansibg($rgb) function. They can detect terminal's color depth and output either 24-bit/256-color/16-color ANSI color escape codes.
But I guess the author wants to avoid using non-core dependencies.
Cool script, anyhow! I spent a lot of times looking at this kind of activity graph on Github.
As already submitted to the Github issues, the ability to show activity of multiple git repos as a single graph would be neat, as we tend work across multiple git repos.
Org is my favorite markup too (mostly because of emacs' org-mode). I certainly hope it picks adoption in the future. One of the downside, however, is its syntax for verbatim paragraph is a bit awkward (requires a colon at the start of each line).