Increase config file compat w.r.t different capitalization

The config file will now detect wrong capitalization of the package name
and emit a warning about it. Furthermore, it will try its best to
subsequently use the package name in the capitalization as used in the
respective find_package call. This should minimize the issues that can
arise from wrong capitalization (such as mismatched capitalization in
the resulting variables).
Nonetheless, there are likely some issues remaining, which is why the
warning requests fixing the capitalization of the package name.

Author: Krzmbrzl

Config.cmake.in

@@ -1,5 +1,36 @@
 include(CMakeFindDependencyMacro)
 
+# ##################################################################################################
+# Handle potential capitalization differences in the project's name
+# ##################################################################################################
+
+set(PROJECT_NAME "@PROJECT_NAME@")
+string(TOLOWER "${PROJECT_NAME}" PROJECT_NAME_LOWER)
+string(TOLOWER "${CMAKE_FIND_PACKAGE_NAME}" CMAKE_FIND_PACKAGE_NAME_LOWER)
+
+if("${PROJECT_NAME_LOWER}" STREQUAL "${CMAKE_FIND_PACKAGE_NAME_LOWER}")
+  if(NOT ("${PROJECT_NAME}" STREQUAL "${CMAKE_FIND_PACKAGE_NAME}"))
+    # The find_package call used a different capitalization of '@PROJECT_NAME@' This can lead to
+    # issues like the config file being found on a platform with a case-insensitive file system but
+    # not on a platform with a case-sensitive filesystem (in case the config file uses the
+    # NameConfig.cmake naming convention rather than name-config.cmake (all-lowercase)). Additional
+    # issues can arise if the caller expects variables such as Name_* to be defined where the
+    # capitalization of Name is important as well.
+    #
+    # We try to circumvent such issues by adapting the capitalization used in the find_package call
+    # but ultimately, the caller should switch to using the proper capitalization.
+    message(
+      AUTHOR_WARNING
+        "Incorrect capitalization in '${CMAKE_FIND_PACKAGE_NAME}'. It should be changed to '@PROJECT_NAME@' to avoid issues."
+    )
+    set(PROJECT_NAME "${CMAKE_FIND_PACKAGE_NAME}")
+  endif()
+endif()
+
+# ##################################################################################################
+# Look up all required dependencies
+# ##################################################################################################
+
 string(REGEX MATCHALL "[^;]+" SEPARATE_DEPENDENCIES "@PROJECT_DEPENDENCIES@")
 
 foreach(dependency ${SEPARATE_DEPENDENCIES})

test/CMakeLists.txt

@@ -9,7 +9,10 @@ project(
 )
 
 if(TEST_INSTALLED_VERSION)
-  find_package(dependency 1.2 REQUIRED)
+  # Note: Wrong capitalization. The project really is called "dependency". However, PackageProject
+  # should have installed workarounds to make this work nonetheless (even on case-sensitive
+  # filesystems)
+  find_package(Dependency 1.2 REQUIRED)
   find_package(header_only 1.0 REQUIRED)
   find_package(namespaced_dependency 4.5.6 REQUIRED)
   find_package(transitive_dependency 7.8.9 REQUIRED)