cmake: Refresh the CMake Config files

This commit fixes a couple issues in the CMake configuration files and uses
native features from CMake:

* libssh-build-tree-settings.cmake is deleted. There was a typo that made
this file unusable, anyway.
* use the macros available in CMakePackageConfigHelpers.cmake to generate
the version file and check that the files exist
* Remove the LIBSSH_THREADS_LIBRARY variable, it used the non-existent
  LIBSSH_THREADS_LIBRARY_NAME variable.
* Fix the in tree build. libssh can be used uninstalled again.

Test plan:
The values were tested after installing the new files and also without running
'make install'.

Signed-off-by: Christophe Giboudeaux <christophe@krop.fr>

CMakeLists.txt

@@ -39,6 +39,9 @@ include(CompilerChecks.cmake)
 include(MacroEnsureOutOfSourceBuild)
 macro_ensure_out_of_source_build("${PROJECT_NAME} requires an out of source build. Please create a separate build directory and run 'cmake /path/to/${PROJECT_NAME} [options]' there.")
 
+# Copy library files to a lib sub-directory
+set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
+
 # search for libraries
 if (WITH_ZLIB)
     find_package(ZLIB REQUIRED)
@@ -116,11 +119,22 @@ install(
 )
 endif (UNIX)
 
-# cmake config files
+# CMake config files
+include(CMakePackageConfigHelpers)
+
 set(LIBSSH_LIBRARY_NAME ${CMAKE_SHARED_LIBRARY_PREFIX}ssh${CMAKE_SHARED_LIBRARY_SUFFIX})
 
-configure_file(${PROJECT_NAME}-config.cmake.in ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config.cmake @ONLY)
-configure_file(${PROJECT_NAME}-config-version.cmake.in ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config-version.cmake @ONLY)
+# libssh-config-version.cmake
+write_basic_package_version_file(libssh-config-version.cmake
+                                 VERSION ${PROJECT_VERSION}
+                                 COMPATIBILITY SameMajorVersion)
+
+# libssh-config.cmake
+configure_package_config_file(${PROJECT_NAME}-config.cmake.in
+                              ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config.cmake
+                              INSTALL_DESTINATION ${CMAKE_INSTALL_DIR}/${PROJECT_NAME}
+                              PATH_VARS INCLUDE_INSTALL_DIR LIB_INSTALL_DIR)
+
 install(
     FILES
         ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config.cmake
@@ -131,10 +145,6 @@ install(
         devel
 )
 
-
-# in tree build settings
-configure_file(libssh-build-tree-settings.cmake.in ${CMAKE_CURRENT_BINARY_DIR}/libssh-build-tree-settings.cmake @ONLY)
-
 if (WITH_EXAMPLES)
     add_subdirectory(examples)
 endif (WITH_EXAMPLES)

libssh-build-tree-settings.cmake.in

@@ -1 +0,0 @@
-set(LIBSSH_INLUDE_DIR @PROJECT_SOURCE_DIR@/include)

libssh-config-version.cmake.in

@@ -1,11 +0,0 @@
-set(PACKAGE_VERSION @PROJECT_VERSION@)
-
-# Check whether the requested PACKAGE_FIND_VERSION is compatible
-if("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}")
-    set(PACKAGE_VERSION_COMPATIBLE FALSE)
-else()
-    set(PACKAGE_VERSION_COMPATIBLE TRUE)
-    if ("${PACKAGE_VERSION}" VERSION_EQUAL "${PACKAGE_FIND_VERSION}")
-        set(PACKAGE_VERSION_EXACT TRUE)
-    endif()
-endif()

libssh-config.cmake.in

@@ -1,15 +1,15 @@
-get_filename_component(LIBSSH_CMAKE_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
+@PACKAGE_INIT@
 
-if (EXISTS "${LIBSSH_CMAKE_DIR}/CMakeCache.txt")
-    # In build tree
-    include(${LIBSSH_CMAKE_DIR}/libssh-build-tree-settings.cmake)
+if (EXISTS "${CMAKE_CURRENT_LIST_DIR}/CMakeCache.txt")
+    # In tree build
+    set_and_check(LIBSSH_INCLUDE_DIR "${CMAKE_CURRENT_LIST_DIR}/include")
+    set_and_check(LIBSSH_LIBRARIES "${CMAKE_CURRENT_LIST_DIR}/lib/@LIBSSH_LIBRARY_NAME@")
 else()
-    set(LIBSSH_INCLUDE_DIR @INCLUDE_INSTALL_DIR@)
+    set_and_check(LIBSSH_INCLUDE_DIR "@PACKAGE_INCLUDE_INSTALL_DIR@")
+    set_and_check(LIBSSH_LIBRARIES "@PACKAGE_LIB_INSTALL_DIR@/@LIBSSH_LIBRARY_NAME@")
 endif()
 
-set(LIBSSH_LIBRARY @LIB_INSTALL_DIR@/@LIBSSH_LIBRARY_NAME@)
-set(LIBSSH_LIBRARIES @LIB_INSTALL_DIR@/@LIBSSH_LIBRARY_NAME@)
+# For backward compatibility
+set(LIBSSH_LIBRARY ${LIBSSH_LIBRARIES})
 
-set(LIBSSH_THREADS_LIBRARY @LIB_INSTALL_DIR@/@LIBSSH_THREADS_LIBRARY_NAME@)
-
-mark_as_advanced(LIBSSH_LIBRARIES LIBSSH_INCLUDE_DIR)
+mark_as_advanced(LIBSSH_LIBRARIES LIBSSH_LIBRARY LIBSSH_INCLUDE_DIR)