When there’s a merge conflict in Mercurial, TortoiseHG will give you the option to ‘take local’ or ‘take other’ in addition to resolving the conflict.
However, sometimes you may want to ‘take local’ or ‘take other’ when there’s no merge conflict.
To take local:
hg merge --tool internal:local <rev>
To take other:
hg merge --tool internal:other <rev>