def get_alphas(revision_str):
    """Return a tuple of the first non-digit characters of a revision (which
    may be empty) and the remaining characters."""
    # get the index of the first digit
    for i, char in enumerate(revision_str):
        if char.isdigit():
            if i == 0:
                return '', revision_str
            return revision_str[0:i], revision_str[i:]
    # string is entirely alphas
    return revision_str, ''