While deploying "on save" checks either timestamp or the hash of content(?), it make sense to add a way how to enforce deployment.
Example: I need to merge changes from a sandbox to another. I have files from the first sandbox and a project with the files of the target sandbox. If I just copy over the files with those with the change, save doesn't trigger deploy all the time.
If I had a button "Enforce deploy of this file", it'd make my life a bit easier.