Optimize finding root of repo

[jacekv]

Lot's of function have the following code in the beginning:

try:
        repo_root_path = get_repo_root_path()
    except NoRepositoryError as nre:
        print(nre)
        exit(1)

All this code does is to locate the path to the .git folder. If there is none, there is no repository.
This should be done before calling the functions and the data should be passed to the functions itself!