Rewrote the logic for pre-filtering files based on timestamps/metadata to be more verbose and well documented.
Fixed an issue where `--check-filetime-only` also checked the file size, which was not present due to the reduced query used to grab only the lastmodified information.
Fixed a problem where the check for existing metadata was wrong and produced a warning.
This fixes#3204
This handles some of #3194
Kenneth Skovhede
52cb9fb1f9