Commit references are ignored by repo commit-file and the web editor #210

ProcessCommitMessages runs from the post-receive path (internal/hookd/hookd.go) and from a merge (internal/control/mr.go). A commit made by repo commit-file or the web editor (internal/control/commitfile.go) lands on the default branch without either, so Closes #N in its message closes nothing and a bare #N leaves no reference comment.

Decide whether those paths should call it (with the session's scope, as the merge path does) or whether "the editor does not act on references" is the rule; record either way.

Found during the #203 review.