Process restart with `enumerateOnStartup` set to true causes all the notes getting synced again

[deepal]

If the enumerateOnStartup is set to true and process is restarted due to some issue, the entire enumeration process happens again (even for the already synced notes).

The best way to do this is:

• keep the metadata file always in-sync
• Verify the note's checksum with the metadata file's corresponding checksum for the file
• Sync only if the checksum is changed