S3FileSystem.checksum() returns different values if file is moved to a new bucket

[gdzelinka]

The value of S3FileSystem.checksum() changes when a file is moved to a new location even if the file is not modified.

I have a file at s3://path/file
I copy that file to s3://path/a/file
The values of S3FileSystem.checksum('s3://path/file) and S3FileSystem.checksum('s3://path/a/file') are different when they should be the same.

[martindurant]

Although called "checksum", this is in fact the ETag and should be interpreted as a unique identifier of a version. The doc says:

        Unique value for current version of file

        If the checksum is the same from one moment to another, the contents
        are guaranteed to be the same. If the checksum changes, the contents
        *might* have changed.

[martindurant]

S3 might also provide content checksums (sha, md5, crc) and check this during an upload operation.