Doesn't git use hashes also? The old hash could redirect to the new "commit" hash, keeping the cycle and allowing for updates at the same time. One of those updates could be the page "changelog".
The HEAD of a repository is like a pointer to the hash of a commit. You may think of HEAD like a repointable alias. `cat .git/refs/heads/master` in any of your git repositories to see what I mean.
Not true! With git time-travel, you can refer to a future commits in the commit message. Eg:
$ git log --oneline HEAD~2..HEAD
9428c8c I am the child
cdd3ab5 I am the parent of 9428c8
:p
For anyone curious, this uses the same idea as the "guess-and-check" approach spullara mentioned: https://news.ycombinator.com/item?id=953569
It changes the content of the commit (by iterating the hash in the commit message itself) until the hash of the child commit matches. A big part of the trick is that it only looks at a prefix of the hash, so the search space is much smaller than the full SHA1 hash.