Add an ExternalData_NO_SYMLINKS to enable use of copies instead of
symlinks to populate the real data files behind a DATA{} reference.
This will be useful on UNIX-like systems when the underlying filesystem
does not actually support symbolic links.
Suggested-by: Matt McCormick <matt.mccormick@kitware.com>
Add support for a special URL template to map the fetch operation
to a project-specified .cmake script insead of using file(DOWNLOAD).
Extend the Module.ExternalData test to cover the behavior.
Extend the RunCMake.ExternalData test to cover error cases.
Take files we previously distributed in ITK 4.3.1:
CMake/ExternalData.cmake
CMake/ExternalData_config.cmake.in
and add them for distribution in upstream CMake. Update the copyright
notice block format to follow CMake conventions.
Brad King