not stored in git (the value of revision history in issues is probably pretty low), but they are accessible via API, and fairly easily exportable [1]

[1] https://gist.github.com/unbracketed/3380407

I actually do this in many of my projects using BugsEverywhere [1]. Distributed bug-tracking is great when you're travelling ... or choose to be off-line.

[1] http://www.bugseverywhere.org/

It's very nice. You can use your fav editor and update pages, then push the changes back up and they appear in the wiki.

With a few plugins and some hacking, you can get vim to just browse the wiki too. (I'm currently working on getting my scripts for this into a state that is useful).

Unrelated - there are some plugins to use the github api to browse tickets in vim too.

(note not all of these workflows make sense as a primary way of using them, but they are still useful at times).