fix: GIT_TAG not parsed inside CPMFindPackage (#159)

When using CPMFindPackage, if no VERSION is given then GIT_TAG is used as fallback if defined, which is a good idea.
The issue is that GIT_TAG is missing inside the oneValueArgs variable therefore GIT_TAG is not parsed. This is resolved by this little change.

README.md

@@ -155,6 +155,8 @@ export CPM_SOURCE_CACHE=$HOME/.cache/CPM
 
 Note that passing the variable as a configure option to CMake will always override the value set by the environmental variable.
 
+You can use `CPM_SOURCE_CACHE` on GitHub Actions workflows [cache](https://github.com/actions/cache) and combine it with ccache, to make your CI faster. See the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/Caching-with-CPM.cmake-and-ccache-on-GitHub-Actions) for more info.
+
 ### CPM_DOWNLOAD_ALL
 
 If set, CPM will forward all calls to `CPMFindPackage` as `CPMAddPackage`.
@@ -196,7 +198,6 @@ cmake --build build --target cpm-update-package-lock
 
 See the [wiki](https://github.com/TheLartians/CPM.cmake/wiki/Package-lock) for more info.
 
-
 ## Built with CPM.cmake
 
 Some amazing projects that are built using the CPM.cmake package manager. 

cmake/CPM.cmake

@@ -119,6 +119,7 @@ function(CPMFindPackage)
   set(oneValueArgs
     NAME
     VERSION
+    GIT_TAG
     FIND_PACKAGE_ARGUMENTS
   )