ns3_traces, = config.getElementsByTagName("ns-3-traces")

    except ValueError:

        print "Note: configuring ns-3 without regression traces"

    else:

        cmd.extend([

                "--with-regression-traces", os.path.join("..", ns3_traces.getAttribute("dir")),

                ])

    try:

#

# The directory in which the tarball of the reference traces lives.  This is

# used if Mercurial is not on the system.

#

REGRESSION_TRACES_URL = "http://www.nsnam.org/releases/"

#

# The path to the Mercurial repository used to find the reference traces if

# we find "hg" on the system.  We expect that the repository will be named

# identically to refDirName below

#

REGRESSION_TRACES_REPO = "http://code.nsnam.org/"

#

# Name of the local directory where the regression code lives.

#

REGRESSION_DIR = "regression"

#

# The last part of the path name to use to find the regression traces.  The

# path will be APPNAME + '-' + VERSION + REGRESSION_SUFFIX, e.g.,

# ns-3-dev-ref-traces

#

REGRESSION_SUFFIX = "-ref-traces"

#

# The last part of the path name to use to find the regression traces tarball.

# path will be APPNAME + '-' + VERSION + REGRESSION_SUFFIX + TRACEBALL_SUFFIX,

# e.g., ns-3-dev-ref-traces.tar.bz2

#

TRACEBALL_SUFFIX = ".tar.bz2"

    # add regression traces

    traces_dir = config.getElementsByTagName("ns-3-traces")[0].getAttribute("dir")

    new_traces_dir = "ns-%s-ref-traces" % ns3_version

    new_config.getElementsByTagName("ns-3-traces")[0].setAttribute("dir", new_traces_dir)    

    def dir_excl(reldirpath, dirname):

        if dirname[0] == '.':

            return True

        return False

    def file_excl(reldirpath, filename):

        if filename.startswith('.'):

            return True

        return False

    print "Adding %s as %s" % (traces_dir, os.path.join(dist_dir, new_traces_dir))

    tar_add_tree(tar, traces_dir, os.path.join(dist_dir, new_traces_dir), dir_excl, file_excl)

def get_regression_traces(ns3_dir, regression_branch):

    print """

    #

    # Get the regression traces

    #

    """

    # ns3_dir is the directory into which we cloned the repo

    # regression_branch is the repo in which we will find the traces.  Variations like this should work:

    #  ns-3-dev-ref-traces

    #  craigdo/ns-3-dev-ref-traces

    #  craigdo/ns-3-tap-ref-traces

    regression_traces_dir = os.path.split(regression_branch)[-1]

    regression_branch_url = constants.REGRESSION_TRACES_REPO + regression_branch

    print "Synchronizing reference traces using Mercurial."

    try:

        if not os.path.exists(regression_traces_dir):

            run_command(["hg", "clone", regression_branch_url, regression_traces_dir])

        else:

            run_command(["hg", "-q", "pull", "--cwd", regression_traces_dir, regression_branch_url])

            run_command(["hg", "-q", "update", "--cwd", regression_traces_dir])

    except OSError: # this exception normally means mercurial is not found

        if not os.path.exists(regression_traces_dir_name):

            traceball = regression_tbranch + constants.TRACEBALL_SUFFIX

            print "Retrieving " + traceball + " from web."

            urllib.urlretrieve(constants.REGRESSION_TRACES_URL + traceball, traceball)

            run_command(["tar", "-xjf", traceball])

            print "Done."

    return regression_traces_dir

    parser.add_option("-r", "--regression-branch", dest="regression_branch", default="ns-3-dev-ref-traces",

                      help="Name of the ns-3 regression traces repository", metavar="REGRESSION_BRANCH_NAME")

    # -- download regression reference traces for NS-3 --

    try:

        traces_dir = get_regression_traces(ns3_dir, options.regression_branch)

    except CommandError:

        print " *** Did not fetch regression reference traces; regression testing will not be available."

    else:

        traces_config = config.documentElement.appendChild(config.createElement("ns-3-traces"))

        traces_config.setAttribute("dir", traces_dir)

        traces_config.setAttribute("branch", options.regression_branch)

     By default, the regression traces will be cloned from the usual

     http://code.nsnam.org/ns-3-dev-ref-traces into a directory

     ns-3-dev-ref-traces in the allinone directory.  You can override

     this using the -r command line option.  For example,

       ./download.py -n craigdo/ns-3-tap -r craigdo/ns-3-tap-ref-traces

     will clone the repository http://code.nsnam.org/craigdo/ns-3-tap

     into the allinone directory and also clone the reference traces

     from the http://code.nsnam.org/craigdo/ns-3-tap-ref-traces repo.