Retrieve the content of a file in an old commit and returns it.

    Ketword Arguments:
        :gitref: (str) -- full reference of the git commit
        :filename: (str) -- name (full path) of the file

    Returns:
        str -- content of the file

def read_committed_file(gitref, filename):
    """Retrieve the content of a file in an old commit and returns it.

    Ketword Arguments:
        :gitref: (str) -- full reference of the git commit
        :filename: (str) -- name (full path) of the file

    Returns:
        str -- content of the file
    """
    repo = Repo()
    commitobj = repo.commit(gitref)

    blob = commitobj.tree[_delta_dir() + filename]
    return blob.data_stream.read()