ros/catkin — pull request #633 by trainman419 (2014-05-16 23:02:33+00:00)
Title: Add catkin_download functions for build data

Add two functions for downloading data at build time; catkin_download_build_data and catkin_download_extra_data. These are useful for download large data blobs such as binaries or configuration that users don't want to include in their repositories.

This is different from catkin_download_test_data because:

* It always builds, and thus always checks the checksum; re-downloading the file if it has changed
* It isn't hidden behind the CATKIN_ENABLE_TESTING flag
* It's optionally added to the all target so that it runs as part of the normal build
* It adds a REQUIRED option in cmake, which allows the download to fail with a warning, without causing the build to fail completely. This is useful for doing builds when there is no network connection.
* It adds the download_extra_data target, which depends on all of the download targets

Comments welcome.