Would the following be feasible?
Git server sends a Mastodon message (or other ActivityPub message?), containing JSON or other structured data describing a change (which repo, which branch, which commit, ...).
A CI service follows the git server's account and reacts to the message by triggering a build.
Git server does not need to know about the CI service. Any number of CI services could follow the git server. Anyone could set up a CI server, no permission required from git server
@liw Yes, that's completely feasible (replace "mastodon message" with "an object with a type extension indicating a commit" and that plan is solid)
@cwebber Cool. I shall have to find time to do that, then.