Source control can tell you when changes to the pipeline were checked in, but they actually take effect when they're applied with 'fly set-pipeline'. That may be before or after they were checked in. Perhaps a sensible team would set up a pipeline to watch the pipeline repository for changes and apply them automatically. Mine hasn't.

> Concourse boils the unit of extension down to "resources"

Which you can only actually use by forking the Concourse BOSH release to add them to the workers [1]. I'm not sure i'd honestly call it a point of extension.

[1] https://github.com/concourse/concourse/blob/master/jobs/grou...