This is used e.g. to update specifically to ISL 0.16.1 although newer revisions exist in the official repository. llvm-svn: 257895
The script will checkout the most recent master from http://repo.or.cz/isl.git into /tmp, create a distribution tarball, and extract it as replacement of lib/External/isl. After that it can be committed to the Polly repository. llvm-svn: 254497