cmake: Change CMake package configuration variable name prefix to GFLAGS_

cmake/config.cmake.in

 ## gflags CMake configuration file
 
 # library version information
-set (@PACKAGE_NAME@_VERSION_STRING "@PACKAGE_VERSION@")
-set (@PACKAGE_NAME@_VERSION_MAJOR  @PACKAGE_VERSION_MAJOR@)
-set (@PACKAGE_NAME@_VERSION_MINOR  @PACKAGE_VERSION_MINOR@)
-set (@PACKAGE_NAME@_VERSION_PATCH  @PACKAGE_VERSION_PATCH@)
+set (@PACKAGE_PREFIX@_VERSION_STRING "@PACKAGE_VERSION@")
+set (@PACKAGE_PREFIX@_VERSION_MAJOR  @PACKAGE_VERSION_MAJOR@)
+set (@PACKAGE_PREFIX@_VERSION_MINOR  @PACKAGE_VERSION_MINOR@)
+set (@PACKAGE_PREFIX@_VERSION_PATCH  @PACKAGE_VERSION_PATCH@)
 
 # import targets
 include ("${CMAKE_CURRENT_LIST_DIR}/@PACKAGE_NAME@-export.cmake")
@@ -18,94 +18,119 @@ get_filename_component (_INSTALL_PREFIX "${CMAKE_CURRENT_LIST_DIR}/@INSTALL_PREF
 # Newer versions of CMake set the INTERFACE_INCLUDE_DIRECTORIES property
 # of the imported targets. It is hence not necessary to add this path
 # manually to the include search path for targets which link to gflags.
-set (@PACKAGE_NAME@_INCLUDE_DIR "${_INSTALL_PREFIX}/@INCLUDE_INSTALL_DIR@")
+set (@PACKAGE_PREFIX@_INCLUDE_DIR "${_INSTALL_PREFIX}/@INCLUDE_INSTALL_DIR@")
 
 # default settings
-if (NOT DEFINED @PACKAGE_NAME@_SHARED)
-  if (TARGET @PACKAGE_NAME@-static OR TARGET @PACKAGE_NAME@_nothreads-static)
-    set (@PACKAGE_NAME@_SHARED FALSE)
+if (NOT DEFINED @PACKAGE_PREFIX@_SHARED)
+  if (DEFINED @PACKAGE_NAME@_SHARED)
+    set (@PACKAGE_PREFIX@_SHARED ${@PACKAGE_NAME@_SHARED})
+  elseif (TARGET @PACKAGE_NAME@-static OR TARGET @PACKAGE_NAME@_nothreads-static)
+    set (@PACKAGE_PREFIX@_SHARED FALSE)
   else ()
-    set (@PACKAGE_NAME@_SHARED TRUE)
+    set (@PACKAGE_PREFIX@_SHARED TRUE)
   endif ()
 endif ()
-if (NOT DEFINED @PACKAGE_NAME@_NOTHREADS)
-  if (TARGET @PACKAGE_NAME@-static OR TARGET @PACKAGE_NAME@-shared)
-    set (@PACKAGE_NAME@_NOTHREADS FALSE)
+if (NOT DEFINED @PACKAGE_PREFIX@_NOTHREADS)
+  if (DEFINED @PACKAGE_NAME@_NOTHREADS)
+    set (@PACKAGE_PREFIX@_NOTHREADS ${@PACKAGE_NAME@_NOTHREADS})
+  elseif (TARGET @PACKAGE_NAME@-static OR TARGET @PACKAGE_NAME@-shared)
+    set (@PACKAGE_PREFIX@_NOTHREADS FALSE)
   else ()
-    set (@PACKAGE_NAME@_NOTHREADS TRUE)
+    set (@PACKAGE_PREFIX@_NOTHREADS TRUE)
   endif ()
 endif ()
 
 # choose imported library target
-if (NOT @PACKAGE_NAME@_TARGET)
-  if (@PACKAGE_NAME@_SHARED)
-    if (@PACKAGE_NAME@_NOTHREADS)
-      set (@PACKAGE_NAME@_TARGET @PACKAGE_NAME@_nothreads-shared)
+if (NOT @PACKAGE_PREFIX@_TARGET)
+  if (@PACKAGE_NAME@_TARGET)
+    set (@PACKAGE_PREFIX@_TARGET ${@PACKAGE_NAME@_TARGET})
+  elseif (@PACKAGE_PREFIX@_SHARED)
+    if (@PACKAGE_PREFIX@_NOTHREADS)
+      set (@PACKAGE_PREFIX@_TARGET @PACKAGE_NAME@_nothreads-shared)
     else ()
-      set (@PACKAGE_NAME@_TARGET @PACKAGE_NAME@-shared)
+      set (@PACKAGE_PREFIX@_TARGET @PACKAGE_NAME@-shared)
     endif ()
   else ()
-    if (@PACKAGE_NAME@_NOTHREADS)
-      set (@PACKAGE_NAME@_TARGET @PACKAGE_NAME@_nothreads-static)
+    if (@PACKAGE_PREFIX@_NOTHREADS)
+      set (@PACKAGE_PREFIX@_TARGET @PACKAGE_NAME@_nothreads-static)
     else ()
-      set (@PACKAGE_NAME@_TARGET @PACKAGE_NAME@-static)
+      set (@PACKAGE_PREFIX@_TARGET @PACKAGE_NAME@-static)
     endif ()
   endif ()
 endif ()
-if (NOT TARGET ${@PACKAGE_NAME@_TARGET})
-  message (FATAL_ERROR "Your @PACKAGE_NAME@ installation does not contain a ${@PACKAGE_NAME@_TARGET} library target!"
-                       " Try a different combination of @PACKAGE_NAME@_SHARED and @PACKAGE_NAME@_NOTHREADS.")
+if (NOT TARGET ${@PACKAGE_PREFIX@_TARGET})
+  message (FATAL_ERROR "Your @PACKAGE_NAME@ installation does not contain a ${@PACKAGE_PREFIX@_TARGET} library target!"
+                       " Try a different combination of @PACKAGE_PREFIX@_SHARED and @PACKAGE_PREFIX@_NOTHREADS.")
 endif ()
 
 # add more convenient "@PACKAGE_NAME@" import target
 if (NOT TARGET @PACKAGE_NAME@)
-  if (@PACKAGE_NAME@_SHARED)
+  if (@PACKAGE_PREFIX@_SHARED)
     add_library (@PACKAGE_NAME@ SHARED IMPORTED)
   else ()
     add_library (@PACKAGE_NAME@ STATIC IMPORTED)
   endif ()
-  # INTERFACE_INCLUDE_DIRECTORIES
-  get_target_property (_@PACKAGE_NAME@_INCLUDES ${@PACKAGE_NAME@_TARGET} INTERFACE_INCLUDE_DIRECTORIES)
-  if (_@PACKAGE_NAME@_INCLUDES)
-    set_target_properties(@PACKAGE_NAME@ PROPERTIES
-      INTERFACE_INCLUDE_DIRECTORIES "${_@PACKAGE_NAME@_INCLUDES}"
-    )
-  endif ()
-  unset (_@PACKAGE_NAME@_INCLUDES)
-  # set configuration specific properties
-  get_target_property (_@PACKAGE_NAME@_CONFIGURATIONS ${@PACKAGE_NAME@_TARGET} IMPORTED_CONFIGURATIONS)
-  set_target_properties (@PACKAGE_NAME@ PROPERTIES IMPORTED_CONFIGURATIONS "${_@PACKAGE_NAME@_CONFIGURATIONS}")
-  foreach (_@PACKAGE_NAME@_CONFIG IN LISTS _@PACKAGE_NAME@_CONFIGURATIONS)
-    # IMPORTED_LOCATION_<config>
-    get_target_property (_@PACKAGE_NAME@_LOCATION ${@PACKAGE_NAME@_TARGET} IMPORTED_LOCATION_${_@PACKAGE_NAME@_CONFIG})
-    if (_@PACKAGE_NAME@_LOCATION)
-      set_target_properties(@PACKAGE_NAME@ PROPERTIES
-        IMPORTED_LOCATION_${_@PACKAGE_NAME@_CONFIG} "${_@PACKAGE_NAME@_LOCATION}"
-      )
-    endif ()
-    unset (_@PACKAGE_NAME@_LOCATION)
-    # IMPORTED_LINK_INTERFACE_LANGUAGES_<config> (static)
-    get_target_property (_@PACKAGE_NAME@_LANGUAGES ${@PACKAGE_NAME@_TARGET} IMPORTED_LINK_INTERFACE_LANGUAGES_${_@PACKAGE_NAME@_CONFIG})
-    if (_@PACKAGE_NAME@_LANGUAGES)
+  # copy INTERFACE_* properties
+  foreach (_@PACKAGE_PREFIX@_PROPERTY_NAME IN ITEMS
+    COMPILE_DEFINITIONS
+    COMPILE_FEATURES
+    COMPILE_OPTIONS
+    INCLUDE_DIRECTORIES
+    LINK_LIBRARIES
+    POSITION_INDEPENDENT_CODE
+  )
+    get_target_property (_@PACKAGE_PREFIX@_PROPERTY_VALUE ${@PACKAGE_PREFIX@_TARGET} INTERFACE_${_@PACKAGE_PREFIX@_PROPERTY_NAME})
+    if (_@PACKAGE_PREFIX@_PROPERTY_VALUE)
       set_target_properties(@PACKAGE_NAME@ PROPERTIES
-        IMPORTED_LINK_INTERFACE_LANGUAGES_${_@PACKAGE_NAME@_CONFIG} "${_@PACKAGE_NAME@_LANGUAGES}"
+        INTERFACE_${_@PACKAGE_PREFIX@_PROPERTY_NAME} "${_@PACKAGE_PREFIX@_PROPERTY_VALUE}"
       )
     endif ()
-    unset (_@PACKAGE_NAME@_LANGUAGES)
-    # IMPORTED_SONAME_<config> (shared)
-    get_target_property (_@PACKAGE_NAME@_SONAME ${@PACKAGE_NAME@_TARGET} IMPORTED_SONAME_${_@PACKAGE_NAME@_CONFIG})
-    if (_@PACKAGE_NAME@_SONAME)
-      set_target_properties(@PACKAGE_NAME@ PROPERTIES
-        IMPORTED_SONAME_${_@PACKAGE_NAME@_CONFIG} "${_@PACKAGE_NAME@_SONAME}"
-      )
-    endif ()
-    unset (_@PACKAGE_NAME@_SONAME)
   endforeach ()
-  unset (_@PACKAGE_NAME@_CONFIGURATIONS)
+  # copy IMPORTED_*_<CONFIG> properties
+  get_target_property (_@PACKAGE_PREFIX@_CONFIGURATIONS ${@PACKAGE_PREFIX@_TARGET} IMPORTED_CONFIGURATIONS)
+  set_target_properties (@PACKAGE_NAME@ PROPERTIES IMPORTED_CONFIGURATIONS "${_@PACKAGE_PREFIX@_CONFIGURATIONS}")
+  foreach (_@PACKAGE_PREFIX@_PROPERTY_NAME IN ITEMS
+    LOCATION
+    LINK_DEPENDENT_LIBRARIES
+    LINK_INTERFACE_LIBRARIES
+    LINK_INTERFACE_LANGUAGES 
+    LINK_INTERFACE_MULTIPLICITY
+    NO_SONAME
+    SONAME
+  )
+    foreach (_@PACKAGE_PREFIX@_CONFIG IN LISTS _@PACKAGE_PREFIX@_CONFIGURATIONS)
+      get_target_property (_@PACKAGE_PREFIX@_PROPERTY_VALUE ${@PACKAGE_PREFIX@_TARGET} IMPORTED_${_@PACKAGE_PREFIX@_PROPERTY_NAME}_${_@PACKAGE_PREFIX@_CONFIG})
+      if (_@PACKAGE_PREFIX@_PROPERTY_VALUE)
+        set_target_properties(@PACKAGE_NAME@ PROPERTIES
+          IMPORTED_${_@PACKAGE_PREFIX@_PROPERTY_NAME}_${_@PACKAGE_PREFIX@_CONFIG} "${_@PACKAGE_PREFIX@_PROPERTY_VALUE}"
+        )
+      endif ()
+    endforeach ()
+  endforeach ()
+  unset (_@PACKAGE_PREFIX@_CONFIGURATIONS)
+  unset (_@PACKAGE_PREFIX@_CONFIG)
+  unset (_@PACKAGE_PREFIX@_PROPERTY_NAME)
+  unset (_@PACKAGE_PREFIX@_PROPERTY_VALUE)
 endif ()
 
 # alias for default import target to be compatible with older CMake package configurations
-set (@PACKAGE_NAME@_LIBRARIES "${@PACKAGE_NAME@_TARGET}")
+set (@PACKAGE_PREFIX@_LIBRARIES "${@PACKAGE_PREFIX@_TARGET}")
+
+# set @PACKAGE_NAME@_* variables for backwards compatibility
+if (NOT "^@PACKAGE_NAME@$" STREQUAL "^@PACKAGE_PREFIX@$")
+  foreach (_@PACKAGE_PREFIX@_VARIABLE IN ITEMS
+    VERSION_STRING
+    VERSION_MAJOR
+    VERSION_MINOR
+    VERSION_PATCH
+    INCLUDE_DIR
+    LIBRARIES
+    TARGET
+  )
+    set (@PACKAGE_NAME@_${_@PACKAGE_PREFIX@_VARIABLE} "${@PACKAGE_PREFIX@_${_@PACKAGE_PREFIX@_VARIABLE}}")
+  endforeach ()
+  unset (_@PACKAGE_PREFIX@_VARIABLE)
+endif ()
 
 # unset private variables
 unset (_INSTALL_PREFIX)