git-branching

Git: How to merge local branch with remote tracking automatically without fetching

Imagine, I have several branches: master, a, b, c ... Now I'm in master branch and "git pull". This fetches all changes from remote server into origin/master, origin/a, origin/b ... branches and merges CURRENT branch (master) with origin/master. But then I want to switch to A branch and again merge these remote changes from remote track...