How can I include Glean SDK definitions files that do not reside in Git?

[chutten]

The FOGotype (Firefox on Glean Prototype) integration will be sending an empty "prototype" ping every so often. For that to not be rejected by the pipeline, I gather that the Probe Info Service needs to know about it.

From the docs I gather I need to point the scraper at a Git repo that contains a pings.yaml... I think.

Do I need to provide a repo if there isn't a metrics.yaml? What if it's a mercurial repo instead of Git? Does probe-scraper know about pings.yaml files?