Implement Use CMake Header File Sets (#30)

* include folder is not working

* fixed include header

* removed unnecessary directives

* update dockerfile to reflect cmake change

* switch to CMAKE_INSTALL_LIBDIR

* remove INSTALL directive

* Revert "remove INSTALL directive"

This reverts commit f4ff6ac.

* update DESTINATION location

.ci/docker/ubuntu.Dockerfile

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-# Using a non-LTS Ubuntu, just until CMake 3.23 is available on Ubuntu 24.04.
+# Using a non-LTS Ubuntu, just until CMake 3.24 is available on Ubuntu 24.04.
 FROM ubuntu:23.10
 
 # Install dependencies,
@@ -30,5 +30,6 @@ ENV CC="$cc" CXX="$cxx" CMAKE_GENERATOR="Ninja" CMAKE_EXPORT_COMPILE_COMMANDS=on
 RUN ls -lR src
 RUN cmake -B build -S . "$cmake_args"
 RUN cmake --build build --verbose
+RUN cmake --build build --target all_verify_interface_header_sets
 RUN cmake --install build --prefix /opt/beman.exemplar
 RUN find /opt/beman.exemplar -type f

src/beman/exemplar/CMakeLists.txt

@@ -5,20 +5,21 @@ add_library(beman::exemplar ALIAS beman.exemplar)
 
 target_sources(beman.exemplar PRIVATE identity.cpp)
 
-target_include_directories(
-  beman.exemplar
-  PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../../../include>)
+set(INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/)
+
+target_sources(
+  beman.exemplar PUBLIC
+  FILE_SET HEADERS
+  BASE_DIRS ${INCLUDE_DIR}
+  FILES ${INCLUDE_DIR}/beman/exemplar/identity.hpp)
+
+set_target_properties(beman.exemplar PROPERTIES VERIFY_INTERFACE_HEADER_SETS ON)
 
 install(
   TARGETS beman.exemplar
   EXPORT beman.exemplar
-  DESTINATION ${CMAKE_INSTALL_LIBDIR})
-
-install(
-  DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/../../../include/
-  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-  FILES_MATCHING
-  PATTERN "*.hpp")
+  FILE_SET HEADERS
+  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
 if(BUILD_TESTING)
   include(GoogleTest)