meld -- How to refresh display when you have changed one of the files

In Meld's View menu, you can try Refresh (Ctrl+R), but also Reload (Shift+Ctrl+R) to reload the files themselves. Depending on the changes, you may want to try the Reload option. Also, be sure to have gedit make a save to disk in order for Meld to see the change of file contents.

So for newer version of Meld, File/Revert does the requested refresh.