That’s great! The proper way to do so is to request the publisher to add you as the snap’s collaborator so that you have access to the snap’s store backstage (mostly for triggering builds whenever it is needed). The snap recipe hosting repository’s write access is also needed to switch the source-tag property if you maintain multiple risk tracks (stable/candidate/beta/edge).
As for switching source-tag and re-commit them just for rebuilding a snap’s is just too costly for the maintainer (IMO), I made a proposal to let the publisher to override/set the source-tag property of the main Snapcraft part when they needed when triggering the build: Proposal: Allow overriding the source-tag property for an one-time build in the build infrastructure , which should be helpful when you want to publish both the release and development snapshot snaps but can’t bother to commit twice just for receiving a single “snap_name contains outdated Ubuntu packages” mail.
UPDATE: Wow, that’s roughly ~40mails per month 