And it's completely reasonable to assume no one external to the org when it was private would have those hashes.
It sounds like github's antipattern here is retaining a log of all events which may leak these hashes, and is really not an assumption I'd expect a git user to make.
They're a local feature sure. But you already have a list of local commits, just open the .git directory.
Can you connect to a vanilla git server and enumerate every single hash?
> Maybe they should include additional clause about forks there.
It would help but they need much more than a clause about forks.
Ideally they would purge that extra data when making something public.
If you have ssh access yes, but I don't think you can do this with just git (and of course github doesn't provide ssh access to the git repo servers)
The public distribution of commit hashes via their event log seems really irresponsible on github's part to me.
No; just knowing how git works is enough to understand that force-pushing squashed commits or removing branches on remote will not necessarily remove the actual data on remote.
GitHub API (or just using the web UI) only makes these features more obvious. For example, you can find and check commit referenced in MR comments even if it was force-pushed away.
> was deeply surprised about GitHub's brute-forceable short commit IDs
Short commit IDs are not GitHub feature, they are git feature.
> If I use GitHub's web interface to click myself a repository with complex access rights, I assume they have concepts in place to thoroughly enforce these access rights.
Have you ever tried to make private GitHub repository public? There is a clear warning that code, logs and activity history will become public. Maybe they should include additional clause about forks there.