ZCL_ABAPGIT_UTILS refactor unit test (#4451)
ZCL_ABAPGIT_UTILS refactor unit test (#4451)

one method per test case, this makes it possible to see which unit test fails, if something fails

just numbered methods, because I'm lazy

closes #4441
larshp/abapGit,sbcgua/abapGit,larshp/abapGit,sbcgua/abapGit