[mrtngslr]

I don't think this is true today. Git and Mercurial have the same basic model, which means that a commit is immutable because the identity of a commit is determined by its content.

This means that you must re-create a changeset in both systems if you want to "change" it. Mercurial and Git can do this and have been doing it for years. The difference is that Git has a built-in concept of garbage collection whereas Mercurial does not. So commands that modify history in Mercurial must trigger the garbage collection (we call it strip) manually -- and they do, of course.

So you wont see any big difference between 'hg rebase' and 'git rebase'. They both build new commits and remove the old commits (in Git they're removed eventually, in Mercurial they're removed immediatedly, but with a backup if you want to restore the pre-rebase state).

The latest versions of Mercurial has history modification built-in: you can 'hg commit --amend' without enabling any extensions. The changeset evolution concept will take this even further and allow really cool collaborative editing of shared history.