Today I found out that there is a great bzr plugin, called extmerge. Here is a small howto install and use it:

mkdir ~/.bazaar/plugins 
bzr get http://erik.bagfors.nu/bzr-plugins/extmerge/ ~/.bazaar/plugins/extmerge
sudo apt-get install xxdiff

now the next time you get conflicts during merge, you can use the command bzr extmerge $conflicting_file, and xxdiff will present you THIS, OTHER, and BASE. You select each hunk you want to use in the merged file, then choose 'Save as merged' in the menu. Done.

tech ~~DISCUSSION~~