Currently one of the solutions in oc-mirror to keep the state of an operator catalog unchanged is to pin the catalog by digest. 

This process currently is manual and it could be automated by saving a file after processing the latest operator catalog. This file could have date and time as its file name and its content would have the operator catalog digest and all operator and related images digests on that specific run. 

This file could be read by customers by some kind of terminal viewer so they can decide which file to use when multiple files are stored. This file could follow the ImageSetConfiguration structure or could be a different one. 

There are three sub-tasks on this spike:

• Convert automatically the tag to a digest, but in a way that is possible to know for each operator catalog version this digest belongs to (it could be some kind of annotation in the ImageSetConfiguration or in another way.
• Save in a file or a commit (in an immutable way - checksum or git) what catalog digest and version was mirrored, what operator versions were mirrored, what was the workflow (m2m, m2d, or d2m), date and time.
• The customer needs to be able to view the history of what was mirrored with all the stored data. This could work together with the current history to do the tar diff.