def addCommonOptions(parser):
    """
    Add standard command-line options to an argument parser.

    @param parser: An C{ArgumentParser} instance.
    """
    parser.add_argument('--minReads', type=int, default=5, help=
        'The minimum number of reads that must cover a location for it to be considered significant.'
        )
    parser.add_argument('--homogeneousCutoff', type=float, default=0.9,
        help=
        'If the most common nucleotide at a location occurs more than this fraction of the time (i.e., amongst all reads that cover the location) then the location will be considered homogeneous and therefore uninteresting.'
        )
