com.github.gist
is the identifier for the package provider of GitHub Gists.
This provider enables sourcing the contents of a single-file GitHub Gist (ergo, a Gist with only one file).
instdat.repo_owner
The owner of the target Gist.
instdat.repo_name
The identifier of the target Gist. (This is named this way for consistency with com.github and because Gists are technically repositories.)
instdat.repo_ref
The Git reference (a commit) of the target repository.