CMakeLists.txt

cmake_minimum_required(VERSION 3.2...3.27)
# gtml - git tracking meta library
project(gtml
    LANGUAGES CXX)

set(NBL_GTML_TRACKED_TARGETS CACHE INTERNAL "")
set(NBL_GTML_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}" CACHE INTERNAL "")
set(NBL_GTML_PROJECT_NAME "${PROJECT_NAME}" CACHE INTERNAL "")
set(NBL_GTML_STAMP_FILE "${NBL_GTML_BINARY_DIR}/stamp" CACHE INTERNAL "")

# useage notes:
# 1. `add_subdirectory` this project
# 2. use function `NBL_ADD_GIT_TRACKING_META_LIBRARY("name" "GIT_PATH")` to track any git_repo
# 3. call `NBL_GENERATE_GIT_TRACKING_META()` to finalize and configure required headers/sources
# 4. link this anywhere you need `target_link_libraries(TARGET PUBLIC gtml)`
# 5. #include "git_info.h" in your code
# 6. profit

function(NBL_ADD_GIT_TRACKING_META_LIBRARY GTML_NAME GIT_WORKING_DIR)
    if(NOT GTML_NAME MATCHES "^[a-zA-Z0-9_]+$")
        message(SEND_ERROR "Name \"${GTML_NAME}\" contains illegal characters, name needs to match '^[a-zA-Z0-9_]+$' regex")
    endif()
    if(GTML_NAME IN_LIST NBL_GTML_TRACKED_TARGETS)
        message(SEND_ERROR "Name \"${GTML_NAME}\" is already specified")
    endif()

    set(SRC_DIR "${CMAKE_CURRENT_FUNCTION_LIST_DIR}")
    set(PRE_CONFIGURE_FILENAME "template_git_info.cpp.in")
    set(PRE_CONFIGURE_FILE "${SRC_DIR}/${PRE_CONFIGURE_FILENAME}")

    set(GTML_INFO "/* This file is auto-generated by CMake's configure_file function from the template: `${PRE_CONFIGURE_FILENAME}`. * Do not edit this file manually. */")

    set(GTML_TARGET_NAME "${GTML_NAME}_check_git")
    set(POST_CONFIGURE_FILE "${NBL_GTML_BINARY_DIR}/${GTML_NAME}_git_info.cpp")
    set(GIT_STATE_FILE "${CMAKE_CURRENT_BINARY_DIR}/${GTML_NAME}_git-state-hash")
    include("${SRC_DIR}/git_watcher.cmake")

    set(NBL_GTML_TRACKED_TARGETS ${NBL_GTML_TRACKED_TARGETS} "${GTML_NAME}" CACHE INTERNAL "")
endfunction(NBL_ADD_GIT_TRACKING_META_LIBRARY)

# TODO: for QoL auto-generate instead of relying of function call to finalize configuration
# finalize configuration, generates headers
function(NBL_GENERATE_GIT_TRACKING_META)
    set(SRC_DIR "${CMAKE_CURRENT_FUNCTION_LIST_DIR}")

    list(SORT NBL_GTML_TRACKED_TARGETS) 
    
    set(GTML_TARGET_NAMES ${NBL_GTML_TRACKED_TARGETS})
    set(GTML_TARGET_SOURCES ${NBL_GTML_TRACKED_TARGETS})
    set(GTML_ENUMS ${NBL_GTML_TRACKED_TARGETS})
    set(GTML_EXTERNS ${NBL_GTML_TRACKED_TARGETS})
    set(GTML_ARRAY ${NBL_GTML_TRACKED_TARGETS})
    list(TRANSFORM GTML_TARGET_NAMES APPEND _check_git)
    list(TRANSFORM GTML_TARGET_SOURCES REPLACE "^(.+)$" "${NBL_GTML_BINARY_DIR}/\\1_git_info.cpp")
    list(TRANSFORM GTML_ENUMS TOUPPER)
    list(TRANSFORM GTML_ENUMS PREPEND EGRM_)
    string(REGEX REPLACE ";" ", " GTML_ENUMS "${GTML_ENUMS}")
    list(TRANSFORM GTML_EXTERNS REPLACE "^(.+)$" "\nextern const GitInfo \\1_git_info")
    list(TRANSFORM GTML_ARRAY REPLACE "^(.+)$" "\\1_git_info")
    string(REGEX REPLACE ";" ", " GTML_ARRAY "${GTML_ARRAY}")

    set(HEADER_NAME "git_info.h.in")
    set(SOURCE_NAME "git_info.cpp.in")
    
    set(GTML_INFO "/* This file is auto-generated by CMake's configure_file function from the template: `${HEADER_NAME}`.\n * Do not edit this file manually. */")
    configure_file("${SRC_DIR}/${HEADER_NAME}" "${NBL_GTML_BINARY_DIR}/git_info.h" @ONLY)

    set(GTML_INFO "/* This file is auto-generated by CMake's configure_file function from the template: `${SOURCE_NAME}`.\n * Do not edit this file manually. */")
    configure_file("${SRC_DIR}/${SOURCE_NAME}" "${NBL_GTML_BINARY_DIR}/git_info.cpp" @ONLY)

    add_library("${NBL_GTML_PROJECT_NAME}" STATIC ${GTML_TARGET_SOURCES} "${NBL_GTML_BINARY_DIR}/git_info.cpp")
    target_include_directories("${NBL_GTML_PROJECT_NAME}" SYSTEM PUBLIC "${NBL_GTML_BINARY_DIR}")
    set_target_properties("${NBL_GTML_PROJECT_NAME}" PROPERTIES UNITY_BUILD TRUE)
    
    # triggers all git check custom commands each build
    add_custom_target("gtml_git_check" ALL COMMAND "${CMAKE_COMMAND}" -E touch "${NBL_GTML_STAMP_FILE}"
        BYPRODUCTS "${NBL_GTML_STAMP_FILE}"
    )
    add_dependencies("${NBL_GTML_PROJECT_NAME}" "gtml_git_check")

endfunction(NBL_GENERATE_GIT_TRACKING_META)