rails の git pull

$ git pull
remote: Counting objects: 9253, done.e[K
remote: Compe[Krremote: essing objects: 100% (2337/2337), done.e[K
remote: Total 8275 (delta 6192), reused 7898 (delta 5843)e[K
Receiving objects: 100% (8275/8275), 2.08 MiB | 87 KiB/s, done.
Resolving deltas: 100% (6192/6192), completed with 230 local objects.
From git://github.com/rails/rails
   44d721c..e724e3e  2-0-stable -> origin/2-0-stable
   5f52da4..d4eb3c0  2-1-stable -> origin/2-1-stable
   8d24a02..227ee2e  master     -> origin/master
 * [new tag]         v2.1.1     -> v2.1.1
You asked me to pull without telling me which branch you
want to merge with, and 'branch.my-v2.1.0.merge' in
your configuration file does not tell me either.  Please
name which branch you want to merge on the command line and
try again (e.g. 'git pull <repository> <refspec>').
See git-pull(1) for details on the refspec.

If you often merge with the same branch, you may want to
configure the following variables in your configuration
file:

    branch.my-v2.1.0.remote = <nickname>
    branch.my-v2.1.0.merge = <remote-ref>
    remote.<nickname>.url = <url>
    remote.<nickname>.fetch = <refspec>

See git-config(1) for details.