One of the comments we are deleting here said:
// Comparing just the hash is not enough; we need to compare both the
// action and the hash, as the hash could appear multiple times (e.g. in a
// pick and later in a merge).
I don't remember what I was thinking when I wrote this code, but it's nonsense
of course. Maybe I was thinking that the hash that appears in a "merge" todo
would be the hash of the commit that is being merged in (which would then
actually appear in an earlier pick), but it isn't, it's the hash of the merge
commit itself (so that the rebase can reuse its commit message). Which means
that hashes are unique, no need to compare the action.
64eb3d560b