Set the scopes for a commit

Set the scopes a commit impacts.

Prefer this over the pull request variant. Scopes computed for one revision do not describe another, so naming the revision lets a report be matched against the head a pull request actually has. A report for a revision a pull request has already moved past can no longer overwrite what its current head reported; a report is still applied to every open pull request whose head it currently is, which is the normal case.

A report replaces the previous one for that revision in full: all_scopes defaults to false, so omitting it clears a barrier previously reported for the same commit. Send the complete result of your scope computation every time.

Send the pull request's head SHA (github.event.pull_request.head.sha). That is not always the revision your job checked out: on a pull_request event the default checkout is a merge commit, and a report keyed on that SHA matches no pull request head.

A scope name may hold anything except a NUL byte or an unpaired UTF-16 surrogate, neither of which Postgres can store, and is limited to 1024 characters; a report carries at most 10000 of them. A report that breaks any of these is refused in full with a 422 and nothing is stored, so the pull request keeps whatever was reported for it last.