Sometimes you make a merge, and you know that one of the branches is “the right one”, but still you have to specify how to merge each merge conflict. This is a handy way of specifying which branch should be used when conflicts arise:
hg merge --tool internal:other
hg merge --tool internal:local
With other, the branch you are merging from is favoured, with local, the branch you are currently in is favoured.
Resources
http://stackoverflow.com/questions/15269060/mercurial-force-merge-branch