Let's say I have my iCloud Photo Library set up and all uploaded, etc., and the master library file being wherever it is. Now, what would happen if I were to reformat my computer, reinstall OS X, move the library file, or buy a new computer? Would Photos then see the library, see my iCloud credentials, and merge the library, or re-upload all pictures? I ask because if I have a 40GB+ library, I wouldn't want to have it re-upload all pictures just because I moved the library file or bought a new computer there. Can anyone tell me anecdotally what happens in those scenarios? Thanks!