Improve deprecation message

cmake/modules/DuneAddLibrary.cmake

@@ -186,9 +186,10 @@ function(dune_add_library_normal _name)
     if(NOT ARG_EXPORT_NAME)
       message(DEPRECATION
         "The function dune_add_library(<lib> ...) now requires to provide NO_EXPORT or EXPORT_NAME. "
-        "After Dune 2.12, the usage of <lib> as an exported name will be deprecated. "
         "We recommend to choose an export name with a camel title case matching your library name "
-        "(e.g., Common, ISTL, and MultiDomainGrid will be exported as Dune::Common, Dune::ISTL, and Dune::MultiDomainGrid)")
+        "(e.g., Common, ISTL, and MultiDomainGrid will be exported as Dune::Common, Dune::ISTL, and Dune::MultiDomainGrid) "
+        " * Calls to `dune_add_library(<lib> ...)` without export specification will be supported until Dune 2.11"
+        " * Consumption of unscoped targets `<lib>` will be supported until Dune 2.12")
       set(ARG_EXPORT_NAME ${_name})
     endif()
 
@@ -243,9 +244,10 @@ function(dune_add_library_interface _name)
     if(NOT ARG_EXPORT_NAME)
       message(DEPRECATION
         "The function dune_add_library(<lib> ...) now requires to provide NO_EXPORT or EXPORT_NAME. "
-        "After Dune 2.10, the usage of <lib> as an exported name will be deprecated. "
         "We recommend to choose an export name with a camel title case matching your library name "
-        "(e.g., Common, ISTL, and MultiDomainGrid will be exported as Dune::Common, Dune::ISTL, and Dune::MultiDomainGrid)")
+        "(e.g., Common, ISTL, and MultiDomainGrid will be exported as Dune::Common, Dune::ISTL, and Dune::MultiDomainGrid) "
+        " * Calls to `dune_add_library(<lib> ...)` without export specification will be supported until Dune 2.11"
+        " * Consumption of unscoped targets `<lib>` will be supported until Dune 2.12")
       set(ARG_EXPORT_NAME ${_name})
     endif()