Merge pull request #73 from strega-nil/fix-cmakelists

Fix CMakeLists.txt install paths

CMakeLists.txt

@@ -1,22 +1,34 @@
 cmake_minimum_required(VERSION 3.12)
 project(cppitertools VERSION 2.0)
-set(CMAKE_CXX_STANDARD 17)
 
+if(NOT DEFINED ENV{cppitertools_INSTALL_CMAKE_DIR})
+  message(WARNING [[
+The default value of cppitertools_INSTALL_CMAKE_DIR changed recently, from
+  "share/cppitertools/cmake"
+to
+  "share"
+in order to behave better with existing CMake practice.
+
+In order to get the previous behavior, pass
+  -Dcppitertools_INSTALL_CMAKE_DIR=share/cppitertools/cmake
+to the CMake invocation; in order to get the new behavior without the warning,
+pass
+  -Dcppitertools_INSTALL_CMAKE_DIR=share
+explicitly.
+]])
+endif()
 
 # installation directories
 set(cppitertools_INSTALL_INCLUDE_DIR "include" CACHE STRING "The installation include directory")
-set(cppitertools_INSTALL_CMAKE_DIR "share/cppitertools/cmake" CACHE STRING "The installation cmake directory")
-
+set(cppitertools_INSTALL_CMAKE_DIR "share" CACHE STRING "The installation cmake directory")
 
 # define a header-only library
 add_library(cppitertools INTERFACE)
 add_library(cppitertools::cppitertools ALIAS cppitertools)
 
 target_include_directories(cppitertools INTERFACE
-        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
-        $<INSTALL_INTERFACE:${cppitertools_INSTALL_CMAKE_DIR}/cppitertools>
-        )
-
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+  $<INSTALL_INTERFACE:${cppitertools_INSTALL_INCLUDE_DIR}/cppitertools>)
 
 # require C++17
 target_compile_features(cppitertools INTERFACE cxx_std_17)
@@ -29,13 +41,19 @@ include(CMakePackageConfigHelpers)
 write_basic_package_version_file(cppitertools-config-version.cmake COMPATIBILITY SameMajorVersion)
 
 # install and export target
-install(TARGETS cppitertools EXPORT cppitertools-targets)
-
-install(EXPORT cppitertools-targets
-        FILE cppitertools-config.cmake
-        NAMESPACE cppitertools::
-        DESTINATION ${cppitertools_INSTALL_CMAKE_DIR}/cppitertools
-        )
-
-install(FILES ${CMAKE_CURRENT_BINARY_DIR}/cppitertools-config-version.cmake DESTINATION ${cppitertools_INSTALL_CMAKE_DIR})
-install(DIRECTORY . DESTINATION ${cppitertools_INSTALL_INCLUDE_DIR}/cppitertools)
+install(
+  TARGETS cppitertools
+  EXPORT cppitertools-targets)
+
+install(
+  DIRECTORY .
+  DESTINATION ${cppitertools_INSTALL_INCLUDE_DIR}/cppitertools)
+
+install(
+  EXPORT cppitertools-targets
+  FILE cppitertools-config.cmake
+  NAMESPACE cppitertools::
+  DESTINATION ${cppitertools_INSTALL_CMAKE_DIR}/cppitertools)
+install(
+  FILES ${CMAKE_CURRENT_BINARY_DIR}/cppitertools-config-version.cmake
+  DESTINATION ${cppitertools_INSTALL_CMAKE_DIR}/cppitertools)