COPY supports two types of destinations: file and directory. In the event that a single file is to be copied into a layer, I've seen cases where the destination is ./ and cases where the destination is just the filename again.
Assuming that there is no intent to change the filename, is a layer that states COPY filename.txt filename.txt the same as one that states COPY filename.txt ./? If they are the same, are there any special considerations to either method?