Use cmake interface library

CMakeLists.txt

@@ -26,7 +26,7 @@ RETURN()
 
 ENDIF()
 
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.1)
 project(cxxopts)
 
 enable_testing()
@@ -37,9 +37,7 @@ option(CXXOPTS_BUILD_EXAMPLES "Set to ON to build examples" ON)
 option(CXXOPTS_BUILD_TESTS "Set to ON to build tests" OFF)
 
 set(CXXOPTS_LINKER_LIBRARIES "")
-
 set(CXXOPTS_USE_UNICODE_HELP FALSE CACHE BOOL "Use ICU Unicode library")
-
 if(CXXOPTS_USE_UNICODE_HELP)
 
   find_package(PkgConfig)
@@ -48,8 +46,17 @@ if(CXXOPTS_USE_UNICODE_HELP)
 
   set(CXXOPTS_LINKER_LIBRARIES "${ICU_LIBRARIES}")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DCXXOPTS_USE_UNICODE")
-
 endif()
 
+add_library(cxxopts INTERFACE)
+target_sources(
+  cxxopts INTERFACE
+  ${CMAKE_SOURCE_DIR}/include/cxxopts/cxxopts.hpp
+  )
+target_include_directories(
+  cxxopts INTERFACE
+  ${CMAKE_SOURCE_DIR}/include
+  )
+
 add_subdirectory(src)
 add_subdirectory(test)

src/CMakeLists.txt

@@ -19,7 +19,8 @@
 # THE SOFTWARE.
 
 if(CXXOPTS_BUILD_EXAMPLES)
-    add_executable(example example.cpp cxxopts.hpp)
+    add_executable(example example.cpp)
+    target_link_libraries(example PRIVATE cxxopts)
 
     if (MSVC)
         target_compile_options(example PUBLIC /W2)
@@ -27,5 +28,3 @@ if(CXXOPTS_BUILD_EXAMPLES)
         target_compile_options(example PUBLIC -std=c++11 -Wall)
     endif()
 endif()
-
-install(FILES cxxopts.hpp DESTINATION include)

src/example.cpp

@@ -24,7 +24,7 @@ THE SOFTWARE.
 
 #include <iostream>
 
-#include "cxxopts.hpp"
+#include "cxxopts/cxxopts.hpp"
 
 int main(int argc, char* argv[])
 {

test/CMakeLists.txt

@@ -1,5 +1,6 @@
 if (CXXOPTS_BUILD_TESTS)
     add_executable(options_test options.cpp)
+    target_link_libraries(options_test PRIVATE cxxopts)
 
     if (MSVC)
         target_compile_options(options_test PUBLIC /W2)

test/options.cpp

@@ -3,7 +3,7 @@
 
 #include <initializer_list>
 
-#include "../src/cxxopts.hpp"
+#include "cxxopts/cxxopts.hpp"
 
 class Argv {
   public: