just a proposal to consider:

Since pga get -i downloads the repositories that were passed through the stdin, imho it could be great if pga list could provide it (without external tools like jq to print only the siva file name)

It could be, for example:

$ pga list --siva | pga get -i

or even using a more general syntax:

$ pga list --columns=sivaFilenames | pga get -i