I've attached the 1-line git-pull-branch script that I just whipped together, in case anybody finds it useful.
On occasion, I need to pull one branch into another branch, inside the same repo. For this case, the objects are already present, so we can skip the git-fetch-script step of git-pull-script completely. I also modify the commit message so that we log the fact that we pulled a branch.
#!/bin/sh
git-resolve-script HEAD $1 "`pwd` branch '$1'"