Comment 1 for bug 202928

There are a couple of patches on the mailing list that should address this.

Basically, the current bzr --revision lookup has 2 "iterate the history to figure out the revno" calls which aren't actually needed.

The patches work around it a bit, and in my testing drops it from 14s => 0.7s.

So it isn't the common ancestor code (Graph.find_unique_lca) it is the "revision_id => revno" (RevisionSpec) code.