Merge topic 'fix-cache-self-assignment'

1cd37527 cmCacheManager: Avoid cache entry self-assignment
326d15a3 cmake: Tolerate missing HELPSTRING on compiler change

Source/cmCacheManager.cxx

@@ -751,11 +751,7 @@ void cmCacheManager::AddCacheEntry(const std::string& key,
     }
   e.SetProperty("HELPSTRING", helpString? helpString :
                 "(This variable does not exist and should not be used)");
-  if (this->Cache[key].Value == e.Value)
-    {
-    this->CMakeInstance->UnwatchUnusedCli(key);
-    }
-  this->Cache[key] = e;
+  this->CMakeInstance->UnwatchUnusedCli(key);
 }
 
 bool cmCacheManager::CacheIterator::IsAtEnd() const

Source/cmake.cxx

@@ -1236,7 +1236,10 @@ int cmake::HandleDeleteCacheVariables(const std::string& var)
     if(ci.Find(save.key))
       {
       save.type = ci.GetType();
-      save.help = ci.GetProperty("HELPSTRING");
+      if(const char* help = ci.GetProperty("HELPSTRING"))
+        {
+        save.help = help;
+        }
       }
     saved.push_back(save);
     }