There's a one-second sleep in the old hook, because the Oven API did not
always record the stream change quickly. Sometimes even that was not
enough. This attempts to work around that by managing the stream list
directly.
10,000 hours mucking with `git filter-repo` and no reasonable use-case
found. On the plus side, anyone looking at this and curious what I nuked
isn't missing much. This lived in a monorepo up until about a week ago.
