git pull and merging.

I have a git.git clone using --use-separate-remote. That means i have
the master branch created by default. Now i need to build git from the
pu branch too. So i created git branch pu remotes/origin/pu.


How how do i track the pu branch using git pull. What i mean is the
master local branch is tracked by default using git pull. Is there a
way to track the local pu branch too.

I looked at git-repo-config and branch.<name>. config variable usage
is confusing. After initial try i concluded that it is to replace
.git/remotes/origin not the requirement i had.