Use "tmpdir" for package build directory. The default is debian/<package>
+=item B<--mainpackage=>I<package>
+
+This little-used option changes the package which debhelper considers the
+"main package", that is, the first one listed in debian/control, and the
+one for which debian/foo files can be used instead of the usual
+debian/package.foo files.
+
=back
=head1 COMMON DEBHELPER OPTIONS