Automatically include git version in software.

CMakeLists.txt

include_directories(${CMAKE_CURRENT_BINARY_DIR}/generated)

#...

add_custom_target(version
	COMMAND ${CMAKE_COMMAND}
	ARGS
		-DOUTPUT=${CMAKE_CURRENT_BINARY_DIR}/generated/version.h
		-P ${CMAKE_CURRENT_SOURCE_DIR}/gen-version.cmake
	WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
	BYPRODUCTS ${CMAKE_CURRENT_BINARY_DIR}/generated/version.h
)

add_dependencies(some-target version)
add_dependencies(maybe-some-other-target version)
# ...

gen-version.cmake

execute_process(COMMAND
	git describe --always --dirty=-modified
	OUTPUT_VARIABLE ver
	OUTPUT_STRIP_TRAILING_WHITESPACE
)
get_filename_component(DIR ${OUTPUT} DIRECTORY)
file(MAKE_DIRECTORY ${DIR})
file(WRITE ${OUTPUT}.new "#ifndef VERSION\n#define VERSION \"${ver}\"\n#endif\n")
execute_process(
	COMMAND
		${CMAKE_COMMAND} -E copy_if_different
		${OUTPUT}.new ${OUTPUT}
)