18.04 – How to delete an aptly published snapshot

Using Ubuntu 18.04 and aptly version 1.4.0.

I am attempting to create a focal mirror using aptly, as follows:

aptly mirror create --architectures="amd64" -filter-with-deps -filter="Installed-Size (<=500000)" focal http://uk.archive.ubuntu.com/ubuntu focal main restricted universe multiverse
aptly mirror update focal
aptly snapshot create focal-latest from mirror focal
aptly publish snapshot --skip-signing focal-latest filesystem:export:export

This seemed to work OK — but I made a small mistake and want to delete the published snapshot and redo it.

How does one do this please? The command line help shows this:

Usage: aptly publish drop <distribution> ((<endpoint>:prefix)

I presume <distribution> is what aptly publish snapshot refers to as <name> but I have been unsuccessful divining the correct format to use. I have tried dozens of combinations, but here are a few, and the results:

$ aptly publish drop focal-latest
ERROR: unable to remove: published repo with storage:prefix/distribution ./focal-latest not found
$ aptly publish drop focal-latest filesystem:export:export
ERROR: unable to remove: published repo with storage:prefix/distribution filesystem:export:export/focal-latest not found
$ aptly publish drop focal-latest filesystem:export
ERROR: unable to remove: published repo with storage:prefix/distribution filesystem:export/focal-latest not found