Now that speed-dreams-data is available as a submodule, this allows the
build system to choose it for in-tree builds. Therefore, CMake will
perform in the following order:
1. Do not search the speed-dreams-data package if SD_ASSUME_DATADIR is
set.
2. Otherwise, do an in-tree build if the submodule has been updated.
3. Otherwise, search for the speed-dreams-data package on standard
locations and CMAKE_PREFIX_PATH and/or CMAKE_FIND_ROOT_PATH.
4. Otherwise, return an error message.
SD_HAS_DATADIR was rendered redundant, so it has been removed. However,
SD_DATADIR_INSTALL_PREFIX was introduced because it would not equal
SD_DATADIR_ABS for in-tree builds, where an installed version of the
speed-dreams-data package is not required.
In-tree builds now allow to generate NSIS installers with both code and
data.
Commit 744677c3a6f3e6c1c463fe55b7b5408355ffe89b from speed-dreams-data
replaced the definition for SD_DATADIR from an absolute path to a
relative path. This was done in order to allow a relative path to be
looked up first by GfApplication::parseOptions() (as required by Windows
and macOS builds), and then look SD_DATADIR_ABS if not found (as
required by in-tree builds).
Now that the project has been migrated from SVN to Git,
the complex logic to determine the project version is now no longer
needed, since Git can achieve the same effect with git-describe(1). [1]
TODO: CPack-related code should be also updated accordingly.
[1]: https://git-scm.com/docs/git-describe
Otherwise, if the speed-dreams-data package is not found, SD_DATADIR
would expand to "/", which is a valid directory that the game would
attempt to look up.
So far, the game assets were located in the same repository as the game
engine. Since data and engine are split into different repositories, now
this project requires users to assign the CMAKE_PREFIX_PATH variable [1]
to indicate the location, only in the case of non-standard locations.
[1]: https://cmake.org/cmake/help/latest/variable/CMAKE_PREFIX_PATH.html
