Merge request title must match the specified regular expression.

A build will be triggered on any new commits in a merge request if its title is matching the regular expression. A build will also get triggered for a non-matching merge request whenever the merge request title changes so that it starts matching the expression.

Regular expression must match the entire merge request title, not just a part of it. For example, to exclude all merge requests with a title starting with "WIP" from triggering builds, specify (?!WIP).+ as a regex.