git

You asked me to pull without telling me which branch you
want to rebase against, and 'branch.master.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 (e.g. 'git pull <repository> <refspec>').
See git-pull(1) for details.

If you often rebase against the same branch, you may want to
use something like the following in your configuration file:
    [branch "master"]
    remote = <nickname>
    merge = <remote-ref>
    rebase = true

    [remote "<nickname>"]
    url = <url>
    fetch = <refspec>

See git-config(1) for details.