Previously, the git version was checked in the initialization of the

GitClient SCM Client. However, with systems that do not have git

installed, this would result in an error being printed that git could

not be found. We now defer determining the installed git version

until we need it, which occurs after we are sure that git is

installed.

Ran unit tests.
Removed git from my system and ran rbt status. Without this patch,

an error message was printed. With it applied, there was no error.