The fix for JENKINS-16025 broke the case when you're trying to upload to S3 a single file without using a wildcard.

For instance:
bucket: bucket/path/to/artifact
source: *.tar.gz

will correctly upload all tar.gz to the destination bucket in the /path/to/artifact folder.

But:
bucket: bucket/path/to/artifact
source: myfile.tar.gz

will unfortunately upload the myfile.tar.gz content into the 'artifact' directory.