"Files are identical" should be "You are comparing the same one file" if both files are the same file
Consider this example:
echo hello > a.txt echo hello > b.txt meld a.txt b.txt
Meld will show "Files are identical" which is correct. But when I do this:
meld a.txt a.txt
Meld will also show "Files are identical", which is technically correct, but I obviously made a mistake. Meld should tell in (in bright red color) that "Hey, you probably made a mistake. You are not comparing 2 files, you accidentally typed filename twice".
This is a common footgun and meld has a chance to spot it. I think it should.
There are some edge cases to consider (like absolute vs. relative path, symlinks, etc.) but I think it should be simple to implement and it would help prevent stupid mistakes.