Specify Branch for Git Pull

[branch "master"]
    remote = origin
    merge = refs/heads/master

or

$ git config branch.master.remote origin
$ git config branch.master.merge refs/heads/master

This tells Git 2 things:

1. When you’re on the master branch, the default remote is origin.
2. When using git pull on the master branch, with no remote and branch specified, use the default remote (origin) and merge in the changes from the master branch.

 

From SO