Merge *to* branch instead of merge *from* branch?

Hi!

My most common use-case of Git is currently somewhere along the lines of

   git checkout master # start from here
   git checkout -b new_branch
   ...edit...
   ...commit...
   git merge master # to make sure I have the latest changes
   ...make sure it all works...
   git checkout master
   git merge new_branch # fast-forwards master to new_branch's HEAD

Is there any way of not having to do the "git checkout master" first? Basically I want a flag to merge or checkout saying that I want to merge my branch into the branch I'm switching to. I can't seem to find any such flag.

(My problem is not that I have to write two commands, the problem is that checking out master and then fast-forwarding it back to where I was is slow, working on a network-mapped share on Win32 as I am, and it causes the ancient compiler I'm using to re-compile nearly everything, which is also slow).