chunker: fix case-insensitive NewObject, test metadata detection #4902
- fix test case FsNewObjectCaseInsensitive (PR #4830)
- continue PR #4917, add comments in metadata detection code
- add warning about metadata detection in user documentation
- change metadata size limits, make room for future development
- hide critical chunker parameters from command line
chunker: improve detection of incompatible metadata #4917
Before this patch chunker required that there is at least one
data chunk to start checking for a composite object.
Now if chunker finds at least one potential temporary or control
chunk, it marks found files as a suspected composite object.
When later rclone tries a concrete operation on the object,
it performs postponed metadata read and decides: is this a native
composite object, incompatible metadata or just garbage.