incompatible repository error messages are unhelpful

How did you reformat your repo? If only I knew how to do that already...

It was empty, so I deleted the .bzr directory and reran init-repo. ;) Sorry for getting your hopes up.

You can use bzr upgrade.

sadly no, it does not work, even worse, it *destroys* the repository when doing so (hopefully, I did this on a copy).

A collaborator of mine just got the same message and doing

bzr upgrade --rich-root-pack

solved the problem (bzr upgrade was not sufficient). Maybe running this command could be suggested in the error message, checking the format of the remote branch if necessary to provide the better help.

Patch sent to list.

The patch changes the behaviour to be like this:

mbp@grace% ./bzr init --development-subtree /tmp/a
mbp@grace% ./bzr init --development /tmp/b
mbp@grace% ./bzr ci -m 'foo' /tmp/a --unchanged
Committing to: /tmp/a/
Committed revision 1.
mbp@grace% ./bzr pull -d /tmp/b /tmp/a
bzr: ERROR: KnitPackRepository('file:///tmp/b/.bzr/repository/')
is not compatible with
KnitPackRepository('file:///tmp/a/.bzr/repository/')
different rich-root support
zsh: exit 3 ./bzr pull -d /tmp/b /tmp/a

I would agree this is not the most helpful message possible as to what you should do next but at least it is giving a specific message about what is wrong. Perhaps we should include a suggestion.