using meld with bazaar extmerge plugin

The excellent extmerge plugin wants to tell the external merge tool about 4 files. Meld only likes to work with three files. Rather than patch meld, I found John's old suggestion on the mailing list and hacked it into a little meld wrapper that gives both bazaar and meld the interfaces they expect. If you are a kdiff3 user, well, extmerge works out of the box for you. I'm partial to meld though, so here is the glue you need (I put this in a script called meld-helper in ~/bin):

# Add this line to your ~/.bazaar/bazaar.conf
# external_merge = 'meld-helper %r %b %t %o'
rm $1
mv $3 $1
meld $2 $4 $1