Oliver Smith authored Feb 07, 2018 and Sören Tempel committed Mar 20, 2018

abuild, as packaged in Alpine Linux, does not depend on git. But when
you use it without git, it will print out errors like the following:

/usr/bin/abuild: line 2554: git: not found

With this commit, it saves the git_path in the beginning (just like
abuild_path). Later in the code it does not try to run git if that
variable is empty.

Notably `abuild rootbld` is already checking whether `abuild-rootbld`
is installed, and that subpackage of `abuild` does already depend on
`git`. So no additional check was added before using `git ` inside
`rootbld`.

Fixes #32