Add `batch-change.name` to changeset templating

[malomarrec]

In the context of creating issues along with campaigns, I'd like to be able to get the batch change name from within a run.

[chrispine]

batch.name?

[malomarrec]

So I'm writing an example of how to create GitHub issues, along with changes, in a declarative way.

There is a container that takes care of checking for existing issues, syncing them, and creating new ones.

Two things would be helpful to add to templating:

• batch.name : passing the name of the campaigns to the step
• batch.run_type : passing whether this is a "preview" or an "apply" to the step

That way I can make it so that my script (1) links to the campaign name, and reuse that as a namespace for tickets (2) create tickets only if "batch.run_type == 'apply'" and skip previews.

[malomarrec]

The only thing I'd miss after that is a
runAfterApplyCompletes step (or applyComplete hook), to trigger a job that will link issues with PRs

Eg.:

{"event":"published"
"repository":"github.com/sourcegraph/sourcegraph"
"changeset_url":"github.com/sourcegraph/sourcegraph/pull/7624"
}

[mrnugget]

batch.run_type doesn't work because while it's executing and while the changesetTemplate is rendered it's still undecided what will happen: the fully rendered batch spec and the changeset specs are uploaded in any case. apply or preview only affects what happens after and not the content of the specs themselves.

[malomarrec]

I see. Then the only way to solve for this use case would be through event hooks I guess.