Improve Version.h handling

Always check for version changes when building. Version.h is only
updated if actually changed.

src/App/CMakeLists.txt

@@ -288,6 +288,8 @@ add_library(FreeCADApp SHARED ${FreeCADApp_SRCS})
 
 target_link_libraries(FreeCADApp ${FreeCADApp_LIBS})
 
+add_dependencies(FreeCADApp fc_version)
+
 SET_BIN_DIR(FreeCADApp FreeCADApp)
 
 if(WIN32)

src/Build/CMakeLists.txt

@@ -6,25 +6,26 @@ set(PACKAGE_WCURL "$WCURL$")
 # If the sources don't include a Version.h then create one
 if (NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/Version.h)
 
-configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Version.h.cmake
-               ${CMAKE_CURRENT_BINARY_DIR}/Version.h.in
-)
-
-EXECUTE_PROCESS(COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_SOURCE_DIR}/src/Tools/SubWCRev.py
-      --srcdir=${CMAKE_SOURCE_DIR} --bindir=${CMAKE_BINARY_DIR}
-      WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
-      OUTPUT_STRIP_TRAILING_WHITESPACE)
-
-fc_copy_file_if_different(
-    "${CMAKE_CURRENT_BINARY_DIR}/Version.h.out"
-    "${CMAKE_CURRENT_BINARY_DIR}/Version.h"
-)
-
-# as fallback if Version.h isn't created for any reason
-if (NOT EXISTS ${CMAKE_CURRENT_BINARY_DIR}/Version.h)
-    set(PACKAGE_WCREF ${PACKAGE_VERSION_PATCH})
     configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Version.h.cmake
-                   ${CMAKE_CURRENT_BINARY_DIR}/Version.h
-    )
-endif (NOT EXISTS ${CMAKE_CURRENT_BINARY_DIR}/Version.h)
+                ${CMAKE_CURRENT_BINARY_DIR}/Version.h.in)
+
+    add_custom_command(
+        OUTPUT  ${CMAKE_CURRENT_BINARY_DIR}/Version.h
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different ${CMAKE_CURRENT_BINARY_DIR}/Version.h.out
+            ${CMAKE_CURRENT_BINARY_DIR}/Version.h
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+        DEPENDS version_check)
+
+    add_custom_command(
+        OUTPUT  version_check
+        COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_SOURCE_DIR}/src/Tools/SubWCRev.py
+        --srcdir=${CMAKE_SOURCE_DIR} --bindir=${CMAKE_BINARY_DIR}
+        WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+
+    ADD_CUSTOM_TARGET(fc_version DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/Version.h)
+
+else (NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/Version.h)
+
+    ADD_CUSTOM_TARGET(fc_version DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/Version.h)
+
 endif (NOT EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/Version.h)