Problemas con Git Pull

Tengo problemas para usar git.

Bifurqué un repository y escribí un código.

Mi amigo clonó eso, hizo algunos cambios y push --all al server.

Ahora quiero ver esos cambios con pull , pero recibo el siguiente post:

 You asked me to pull without telling me which branch you want to merge with, and 'branch.branchName.merge' in your configuration file does not tell me, either. Please specify which branch you want to use on the command line and try again (eg 'git pull <repository> <refspec>'). See git-pull(1) for details. If you often merge with the same branch, you may want to use something like the following in your configuration file: [branch "threshold"] remote = <nickname> merge = <remote-ref> [remote "<nickname>"] url = <url> fetch = <refspec> See git-config(1) for details. 

¿Qué estoy haciendo mal aquí?