Each revision of a source file can have optional tags placed on it. These tags are
typically used for build history, merge history, or release management. These tags are
simple strings and may clutter a revision graph if not important. If tags are set to be
shown inside the revision graph nodes, then they can be filtered based on a regular
expression. The filter can be either to include or exclude the tags that match the
filter based on the show/hide toggle. For proper regular expression syntax, see
http://java.sun.com/javase/6/docs/api/java/util/regex/Pattern.html