Enable YACC for certain branches

Sometimes it is useful to turn on checks only for certain branches and turn them off on all other branches.

YACC has the Exclude Branch Regex feature to specify a regex that can exclude branches from checks. With a little bit of regex magic, this feature can be used to only run YACC on a set of allowlisted branches.

For example, to perform checks on the branches master and release, but no other branch, configure the Exclude Branch Regex option like this:
^(?!master$|release$).*

All branch names other than master and release are excluded, and the checks only apply to those two branches.