tests: convert the 'file://\$TESTTMP' rule to an automatic substitution
The rule only triggered on non Windows platforms, even though Windows also
required an adjustment. Automatic seems better.
The aggressive globbing in test-subrepo-svn.t was found and rewritten by the
substitution.
#require docutils gettext
$ $TESTDIR/check-gendoc zh_CN
checking for parse errors