CPM.cmake

This is the official release of the get_cpm.cmake script, which will be the recommended way to get CPM.cmake. This will reduce the code impact of adding CPM.cmake and allow minimise the amount of third-party code in C++ projects. Thanks to @tueda for the suggestion of caching the download itself (#145).

This release is to test the functionality introduced by #146.

This release is to check that the auto-version feature of #139 works as intended.

Fixes use of the GITLAB_REPOSITORY argument. Relevant PR: #137.

Cached dependencies are now fetched using --depth=1 by default, to minimise bandwidth and configure time. This does not apply when an explicit commit hash is provided.

See #129 and #130 for details and discussion.

Allows overriding the CPM_SOURCE_CACHE per package. This is useful for packages that modify their source directory.

Fixes an issue where a dependency's package lock could override outer declarations.

Adds an optional FORCE parameter used internally to override any external package origin settings.
Allows package lock / declarations to be used with local overrides.

Adds the option to override a dependency per-build through a CMake argument.

Library developers are often in the situation where they work on a locally checked out dependency at the same time as on a consumer. It is now possible to override the consumer's dependency version with the local one by supplying the CMake option CPM_<dependency name>_SOURCE to the build. For example, to use the local version of Dep at the absolute path /path/to/dep, the consumer can be built with cmake -H. -Bbuild -DCPM_Dep_SOURCE=/path/to/dep.

This patch prevents local paths leaking into the package lock and omits dependencies without version information.

The package lock makes it easier to manage and override transitive dependencies. When using a package lock file, dependencies can be updated without modifying the main or other project's CMakeLists.txt.

Usage

After including CPM.cmake, call CPMUsePackageLock(package-lock.cmake) to include package-lock.cmake, if it exists. This file can be created and updated using the new target cpm-update-package-lock. Note that it should be added to version control.

More info can be found in the wiki.

Relevant Issues / PRs: #116, #119

• CPMFindPackage no longer overwrites version info if the package has already been added before.

Packages with the DOWNLOAD_ONLY flag set no longer error when the source directory is already populated.

This allows find_package() to find previously added CPM.cmake modules.

CPM_SOURCE_CACHE should now work offline again and on windows.

From now on, the most recent version of CPM can be downloaded from the according GitHub release as opposed to pulling it from the master branch.