Comment 6 for bug 893509

Why not just use:

    bzr log -rX.. -l1

If X is in the history of the branch it will be displayed, if not an error message should be. Using 'X..' here forces log to search the branch history (since the missing Y in X..Y defaults to the branch tip). Using -l1 ensures you won't get excessive output if the revision is in your branch.