cmake_minimum_required(VERSION ${CMAKE_VERSION})

include(ExternalProject)

ExternalProject_Add(BAR URL https://cmake.org/bar.tar.gz)

ExternalProject_Add(FOO URL https://cmake.org/foo.tar.gz STEP_TARGETS update)
ExternalProject_Add_Step(FOO do_something COMMAND ${CMAKE_COMMAND} -E echo "Doing something")
ExternalProject_Add_Step(FOO do_something_else COMMAND ${CMAKE_COMMAND} -E echo "Doing something else")
ExternalProject_Add_StepTargets(FOO do_something)

# download and do_something_else are not targets, but the file-level
# dependency are set.
ExternalProject_Add_StepDependencies(FOO download BAR)
ExternalProject_Add_StepDependencies(FOO do_something_else BAR)

# update and do_something are targets, therefore both file-level and
# target-level dependencies are set.
ExternalProject_Add_StepDependencies(FOO update BAR)
ExternalProject_Add_StepDependencies(FOO do_something BAR)