key error where no command is specified

[leoll2]

When one invokes git fat without any specific subcommand it is an error, the corresponding out message should be human-readable. Currently the error is:

leoll2:~/aaa > git fat
Traceback (most recent call last):
  File "/usr/local/bin/git-fat", line 1160, in <module>
    run_command(**kwargs)
  File "/usr/local/bin/git-fat", line 1076, in run_command
    fn = kwargs.pop('func').replace("-", "_")
KeyError: 'func'