Add CPM_RESET (#4)

* added CPM_RESET option

* update readme

* Update README.md

cmake/CPM.cmake

@@ -2,10 +2,13 @@ set(_CPM_Dir "${CMAKE_CURRENT_LIST_DIR}")
 
 include(CMakeParseArguments)
 include(${_CPM_Dir}/DownloadProject.cmake)
-
-function(CPMHasPackage) 
   
-endfunction()
+option(CPM_RESET "reset CPM" OFF)
+
+if(${CPM_RESET})
+  message(STATUS "CPM: resetting packages")
+  set(CPM_PACKAGES "" CACHE INTERNAL "CPM Packages")
+endif()
 
 function(CPMAddPackage)
   set(options QUIET)
@@ -16,6 +19,7 @@ function(CPMAddPackage)
     VERSION
     GIT_TAG
     BINARY_DIR
+    UPDATE_DISCONNECTED
   )
 
   set(multiValueArgs "")
@@ -30,6 +34,15 @@ function(CPMAddPackage)
     set(CPM_ARGS_BINARY_DIR ${CMAKE_BINARY_DIR}/CPM-projects/${CPM_ARGS_NAME})
   endif()
 
+  if (NOT CPM_ARGS_UPDATE_DISCONNECTED)
+    if (${CPM_RESET})
+      set(CPM_ARGS_UPDATE_DISCONNECTED OFF)
+    else()
+      set(CPM_ARGS_UPDATE_DISCONNECTED ON)
+    endif()
+  endif()
+
+
   if (NOT CPM_PROJECT_DIR)
     set(CPM_PROJECT_DIR "${CPM_ARGS_BINARY_DIR}")
   endif()

cmake/CPMProject.CMakeLists.cmake.in

@@ -17,7 +17,7 @@ else()
     PROJ @CPM_ARGS_NAME@
     GIT_REPOSITORY @CPM_ARGS_GIT_REPOSITORY@
     GIT_TAG @CPM_ARGS_GIT_TAG@
-    UPDATE_DISCONNECTED 1
+    UPDATE_DISCONNECTED @CPM_ARGS_UPDATE_DISCONNECTED@
     GIT_SHALLOW 1
     PREFIX @CPM_ARGS_BINARY_DIR@/dl
     QUIET