Something like hg transplant? That's what we use on our dev and prod branches.

As the previous poster mentioned, the transplant extension can be used for cherry-picking individual changes from one branch to another. If, however, you always want to pull all the latest changes, the hg merge command will get you there.

The simplest case is when you're using clones to implement branching (since that's the use case Mercurial is designed around). Assuming you've turned on the built-in fetch extension in your .hgrc / Mercurial.ini:

cd ~/src/development
# hack hack hack
hg commit -m "Made some changes"
cd ../production
hg fetch ../development

If you're using local branches:

hg update -C development
# hack hack hack
hg commit -m "Made some changes"
hg update -C production
hg merge development
hg commit -m "Merged from development"