Before this change, TestChunkerS3: tests were failing because our use of
obj.Remove (for "modtime_write_test") created an unexpected extra transfer.
This is because chunker calls operations.Move for removes, which (per its
function comment) is supposed to be only accounted as a check. But because S3
can Copy but not Move, the move falls back to copy and ends up getting counted
as a transfer anyway.
99e8a63df2/fs/operations/operations.go (L506)99e8a63df2/fs/operations/copy.go (L381)
This is probably a bug that should get a more proper fix in operations. But in
the meantime, we can get around it by doing our "modtime_write_test" with its
own unique stats group.
d915f75edf