Store repositories clones

[m-aciek]

I'd like us to store the repositories in a place less transient than a temporary directory (user data? using appdirs?). This would allow us to make a second pass to calculate more accurate month ago progress without cloning everything over). Also it would allow a second pass for generating more detailed information for #58.

[mattwang44]

How about using Action Artifacts (max. retention for the public repos is 90 days)?