I think what you're trying to fix is that your local "master" branch is based on the remote UAC branch, as opposed to the remote trunk. If you're happy to lose your commits, you can simply run the below, which will checkout the trunk and then move the master branch to your current point.
git checkout remotes/trunk
git checkout -B master
If you don't want to lose your commits, git rebase
is your friend. Use the below:
git rebase $(git merge-base remotes/UAC master) master --onto remotes/trunk
This works out the common parent of the UAC branch and the local master branch, makes all the commits from there to the tip of the master branch onto the trunk, then moves the master branch to point there.