ENH: Updated ExternalProject.cmake - When repository is Git, update step will "reset", "pull" and "re-apply patches"

CMake/ExternalProject.cmake

@@ -777,13 +777,21 @@ endfunction(_ep_add_download_command)
 
 
 function(_ep_add_update_command name)
-  ExternalProject_Get_Property(${name} source_dir)
+  ExternalProject_Get_Property(${name} source_dir tmp_dir)
 
   get_property(cmd_set TARGET ${name} PROPERTY _EP_UPDATE_COMMAND SET)
   get_property(cmd TARGET ${name} PROPERTY _EP_UPDATE_COMMAND)
   get_property(cvs_repository TARGET ${name} PROPERTY _EP_CVS_REPOSITORY)
   get_property(svn_repository TARGET ${name} PROPERTY _EP_SVN_REPOSITORY)
   get_property(git_repository TARGET ${name} PROPERTY _EP_GIT_REPOSITORY)
+  
+  # Patch
+  get_property(patch_cmd_set TARGET ${name} PROPERTY _EP_PATCH_COMMAND SET)
+  get_property(patch_cmd TARGET ${name} PROPERTY _EP_PATCH_COMMAND)
+  set(patch_work_dir)
+  if(patch_cmd_set)
+    set(patch_work_dir ${source_dir})
+  endif()
 
   set(work_dir)
   set(comment)
@@ -816,9 +824,37 @@ function(_ep_add_update_command name)
       message(FATAL_ERROR "error: could not find git for pull of ${name}")
     endif()
     set(work_dir ${source_dir})
+
+    # The following script will allow to reset, pull and re-apply patches
+    file(WRITE ${tmp_dir}/${name}-gitupdate.cmake "
+execute_process(
+  COMMAND ${Git_EXECUTABLE} reset --hard HEAD
+  WORKING_DIRECTORY ${work_dir}
+  RESULT_VARIABLE error_code
+  )
+execute_process(
+  COMMAND ${Git_EXECUTABLE} pull
+  WORKING_DIRECTORY ${work_dir}
+  RESULT_VARIABLE error_code
+  )
+if(error_code)
+  message(FATAL_ERROR \"Failed to pull - repository: ${git_repository}\")
+endif()
+if(${patch_cmd_set})
+  execute_process(
+    COMMAND ${patch_cmd}
+    WORKING_DIRECTORY ${patch_work_dir}
+    RESULT_VARIABLE error_code
+    )
+  if(error_code)
+    message(FATAL_ERROR \"Failed to apply patch for ${name}\")
+  endif()
+endif()
+")
+
     set(comment "Performing update step (GIT pull) for '${name}'")
     #get_property(git_revision TARGET ${name} PROPERTY _EP_GIT_REVISION)
-    set(cmd ${Git_EXECUTABLE} pull)
+    set(cmd ${CMAKE_COMMAND} -P ${tmp_dir}/${name}-gitupdate.cmake)
     set(always 1)
   endif()