"Perhaps they are storing build artefacts in the repo."
I guess it depends if you only do "source code" control or "whole version" control.
It seems likely that they hold everything in there so you can track the code, the compiler settings, the resources and of course the test results.
As others have noted there will likely be different branches for "Home" "Small Business" "Enterprise" editions as well
OTOH I'm not so sure that includes Office, Dynamics or the languages.
Biting the hand that feeds IT
