how to modify bzr history

Bazaar follows a "mistakes are part of history" or "append-only" philosophy in both repository and branch history. You may also think of a revision as intrinsically containing the immutable history that precedes it.

If you want to edit a revision you just made, you can "uncommit" it. This built-in command works by rewinding the branch head pointer to the previous revision. As you will see if you do this, the uncommitted revision is not actually deleted, because repositories are append-only. Instead, it is replaced by the new revision you make when you commit again. This does not trickle across the web to people who have already branched or merged the "broken" revision; the fact that forcing potentially malicious updates to all branches is not safe is part of the reason for the "append-only" philosophy.

If you really must edit an old revision, you can branch that revision, uncommit and recommit, then use the rebase plugin (http://bazaar-vcs.org/Rebase) to copy the remaining revisions to your new branch. You may not like the implications of that; see http://failex.blogspot.com/2008/09/what-is-cascading-rebase.html (shameless self-blog-promotion) for a visual explanation of what rebase does.