cmake: re-add Libssh2:libssh2 for compatibiliy + lowercase namespace

- add `libssh2:libssh2` target that selects the shared lib if built,
  otherwise the static one.

- re-add `Libssh2:libssh2` target for compatibility with v1.10.0 and
  earlier. This is an alias for `libssh2:libssh2`.

- keep `libssh2:libssh2_shared` and `libssh2_libssh2_static` targets.

- allow using `find_package(libssh2)` in dependents as an alternative
  to `find_package(Libssh2)`.

Co-authored-by: Radek Brich
Suggested-by: Haowei Hsu

Fixes #1103
Fixes #731
Closes #1104

cmake/libssh2-config.cmake.in

@@ -0,0 +1,10 @@
+# Copyright (C) The libssh2 project and its contributors.
+# SPDX-License-Identifier: BSD-3-Clause
+
+include("${CMAKE_CURRENT_LIST_DIR}/libssh2-targets.cmake")
+
+# Alias for either shared or static library
+add_library(libssh2::libssh2 ALIAS libssh2::@LIB_SELECTED@)
+
+# Compatibility alias
+add_library(Libssh2::libssh2 ALIAS libssh2::@LIB_SELECTED@)

docs/INSTALL_CMAKE.md

@@ -134,8 +134,8 @@ setting it up with libssh2's location. Add the following lines and
 CMake will find libssh2 on your system, set up the necessary paths and
 link the library with your binary.
 
-    find_package(Libssh2 REQUIRED CONFIG)
+    find_package(libssh2 REQUIRED CONFIG)
-    target_link_libraries(my_project_target Libssh2::libssh2)
+    target_link_libraries(my_project_target libssh2::libssh2)
 
 You still have to make libssh2 available on your system first.  You can
 install it in the traditional way shown above, but you do not have to.
@@ -149,13 +149,13 @@ builds your project:
     include(ExternalProject)
 
     ExternalProject_Add(
-        Libssh2
+        libssh2
         URL <libssh2 download location>
         URL_HASH SHA256=<libssh2 archive SHA256>
         INSTALL_COMMAND "")
 
     ExternalProject_Add(
-        MyProject DEPENDS Libssh2
+        MyProject DEPENDS libssh2
         SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/src
         INSTALL_COMMAND "")
 

src/CMakeLists.txt

@@ -143,14 +143,14 @@ install(FILES
 
 if(BUILD_STATIC_LIBS)
   install(TARGETS ${LIB_STATIC}
-    EXPORT Libssh2Config
+    EXPORT libssh2-targets
     RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
     LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
     ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
 endif()
 if(BUILD_SHARED_LIBS)
   install(TARGETS ${LIB_SHARED}
-    EXPORT Libssh2Config
+    EXPORT libssh2-targets
     RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
     LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
     ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
@@ -163,15 +163,21 @@ set(RUNTIME_DEPENDENCIES ${_RUNTIME_DEPENDENCIES} CACHE INTERNAL
 
 # Package config
 
-## During package installation, install Libssh2Config.cmake
+## During package installation, install libssh2-targets.cmake
-install(EXPORT Libssh2Config
+install(EXPORT libssh2-targets
-  NAMESPACE Libssh2::
+  NAMESPACE libssh2::
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/libssh2)
 
 ## During build, register directly from build tree
-# create Libssh2Config.cmake
+# create libssh2-targets.cmake
-export(TARGETS ${libssh2_export} NAMESPACE Libssh2:: FILE Libssh2Config.cmake)
+export(TARGETS ${libssh2_export} NAMESPACE libssh2:: FILE libssh2-targets.cmake)
-export(PACKAGE Libssh2) # register it
+export(PACKAGE libssh2)  # register it
+
+# Generate libssh2-config.cmake into build tree and install it
+configure_file(${CMAKE_SOURCE_DIR}/cmake/libssh2-config.cmake.in libssh2-config.cmake @ONLY)
+install(
+  FILES ${CMAKE_CURRENT_BINARY_DIR}/libssh2-config.cmake
+  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/libssh2)
 
 ## Export a .pc file for client projects not using CMaek
 if(PC_REQUIRES_PRIVATE)
@@ -209,9 +215,9 @@ endif()
 
 include(CMakePackageConfigHelpers)
 write_basic_package_version_file(
-  ${CMAKE_CURRENT_BINARY_DIR}/Libssh2ConfigVersion.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/libssh2-config-version.cmake
   VERSION "${LIBSSH2_VERSION_MAJOR}.${LIBSSH2_VERSION_MINOR}.${LIBSSH2_VERSION_PATCH}"
   COMPATIBILITY SameMajorVersion)
 install(
-  FILES ${CMAKE_CURRENT_BINARY_DIR}/Libssh2ConfigVersion.cmake
+  FILES ${CMAKE_CURRENT_BINARY_DIR}/libssh2-config-version.cmake
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/libssh2)