z3c.repoexternals 0.3

Use the –help option for usage details:

usage: repoexternals [options] url_or_path

Recursively retrieves subversion directory listings from the url or
path and matches directories against a previous set of svn:externals
if provided then against regular expressions and generates
qualifying svn:externals lines.  The defaults generate a set of
svn:externals for all the trunks in a repository and keeps them up
to date with the repository as new trunks are added when the
previous externals are provided thereafter.

options:
  -h, --help            show this help message and exit
  -v, --verbose         Output logging to standard error. Set twice
                        to log debugging messages.
  -p FILE, --previous=FILE
                        If provided, only URLs in the repository not
                        included in the previous externals will be
                        included. If the filename is '-', use
                        standard input.  Valid svn:externals lines
                        beginning with one comment character, '#',
                        will also affect output.  This is useful,
                        for example, to prevent lengthy recursions
                        into directories that are known not to
                        contain any desired matches.  The file is
                        read completely and closed before anything
                        is output, so it is safe to append output to
                        the previous file:
                        "repoexternals -p EXTERNALS.txt http://svn.foo.org/repos/main >>EXTERNALS.txt".
  -i REGEXP, --include=REGEXP
                        Directory names matching this python regular
                        expression will be included in output and
                        will not be descended into.
                        [default: (?i)^((.*)/.+?|.*)/trunk$]
  -e REGEXP, --exclude=REGEXP
                        Directory names matching this python regular
                        expression will be excluded from output and
                        will not be descended into. Include
                        overrides exclude.  [default:
                        (?i)^.*/(branch(es)?|tags?|releases?|vendor|bundles?|sandbox|build|dist)$]
  -m TEMPLATE, --matched-template=TEMPLATE
                        The result of expanding previous file URL
                        matches with the include regular expression
                        through this template is added to the set of
                        previous URLs excluded from output and
                        descending.  The default will add the
                        parents of trunks to the set of previous
                        URLs excluded.  [default: \1]
  -t TEMPLATE, --parent-template=TEMPLATE
                        The result of expanding previous file URL
                        matches with the include regular expression
                        through this template is removed from the
                        set of matched previous URLs excluded from
                        output and descending. The default ensures
                        that directories containing trunks within a
                        directory that contains a trunk are not
                        excluded.  [default: \2]
  -d INT, --depth=INT   The maximum directory depth to descend to.
                        WARNING: large values can greatly increase
                        run time.  [default: 5]
  -s INT, --pool-size=INT
                        The number of concurrent svn clients.
                        WARNING: large values can DOS the
                        repository.  [default: 5]

The source distribution is also a zc.buildout that installs the script locally for use without affecting the system python installation:

$ easy_install --editable --build-directory=foo z3c.repoexternals
$ cd foo
$ python bootstrap/bootstrap.py -v
$ ./bin/buildout -v
$ ./bin/repoexternals --help