This mostly affects OneDrive saves syncing, because it is the only cloud
provider to return 0 as timestamp of (non-)created file. 0 is treated as
EOF in /saves/timestamps file, thus all timestamps after such 0
timestamps were ignored and files were reuploaded as being "new". This
commit also adds more verbose debug information on SavesSyncRequest
decisions making for easier debugging.
1e92e7b9f3