tests: add a new test for testing changing or clearing topics
test-topic.t is getting bigger and bigger. This patch introduces a new test
which includes test for clearing and changing topics.
Since the tests are moved to a new file, this patch, removes those tests from
test-topic.t also.
syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes