Only download files that have changed
Some servers provide an etag which is a unique identifier for the content being served (not always a hash). This adds two new column to the archival, an etag and a last-modified field. If the etag is available in the archival, and we get the same etag from the request, then we will not download the file. The last-modified field is saved for sanity, it isn't yet used with If-Modified-Since in the request. This requires a migration: alter table archival add column etag character varying; alter table archival add column last-modified character varying; Notification of package updates is only done if at least 1 resource was downloaded, to avoid unnecessarily running QA and Packagezip.