avoid stateful operations in virtual bootstrap, which presumably causes occasional crash of drule.ML due to inner syntax pp;
syntax: glob
*~
*.class
*.jar
*.marks
*.orig
*.rej
.DS_Store
.swp
syntax: regexp
^contrib
^heaps/
^browser_info/
^doc/.*\.dvi
^doc/.*\.eps
^doc/.*\.pdf
^doc/.*\.ps
^src/Tools/jEdit/dist/
^Admin/jenkins/ci-extras/target/