This adds support, documentation, and testing for a [[repos.git]]
blueprint section that can be used to install files from a git
repository. It will create an rpm that will be added to the build,
and included in the metadata that can be downloaded. This allows you to
accurately keep track of the source of configuration files and extra
metadata that is added to the build.
The source repo and reference will be listed in the rpm's summary making
it easy to discover on the installed system.
(cherry picked from commit d7b96c8f0f)
Resolves: rhbz#1709594
f5113542b1