Ref T11522. This tries to reduce the cost of rewriting a repository by making handles smarter about rewritten commits.

When a handle references an unreachable commit, try to load a rewrite hint for the commit. If we find one, change the handle name to "OldHash > NewHash" to provide a strong hint that the commit was rewritten and that copy/pasting the old hash (say, to the CLI) won't work.

I think this notation isn't totally self-evident, but users can click it to see the big error message on the page, and it's at least obvious that something weird is going on, which I think is the important part.

Some possible future work:

• Not sure this ("Recycling Symbol") is the best symbol? Seems sort of reasonable but mabye there's a better one.
• Putting this information directly on the hovercard could help explain what this means.