One way to merge in these changes is to pull them into a local branch for review, verifying the changes and then merge to back to master.

# Check out a new branch for integration
git checkout -b merge-requests/21

# Fetch the merge request into this branch
git pull \
  git://gitorious.org/ponyexpress/mainline.git \
  refs/merge-requests/21

# Show the commits, assess they are okay
git log --pretty=oneline --abbrev-commit master..merge-requests/21

# To apply the changes to your branch:
git checkout master
git merge merge-requests/21
git push origin master