Hi,
Thanks to tips from Bob in the past, I know how to download all attachments for all issues from a filter... something like this:
./jira.sh --action runFromIssueList --filter delta-migration-test --common "--action runFromAttachmentList --issue @issue@ --common \"--action getAttachment --issue @issue@ --file \"\"target/@issue@/@attachment@\"\" \" "
Which gets me something like:
target/FOOBAR-123/example.txt
target/FOOBAR-1232/example.pdf
target/FOOBAR-1232/another-one.docx
....
Seems like there should be a way do something similar with an upload. Short of having Jira cli connect for each attachment, any tips? I wish I could just swap "getAttachment" with "addAttachment" and call it a day! 
One other thing -- is there a way to take the output from getAttachmentList, and upload via that? Didn't see any examples for that.