These optional globbing patterns will be matched against the filepath
(not the filename) using grunt.file.isMatch. If any specified globbing
pattern matches, the file won't be processed via the process function.
If true is specified, processing will be prevented.
The source file contents and file path are passed into this function,
whose return value will be used as the destination file's contents. If
this function returns false, the file copy will be aborted.