Do not switch to master branch in pull()
Add --track to git checkout, when checking out a remote branch to track.

The ohai and facter modules use /usr/bin/logger to log the fact that
they have been invoked.  I added 'import os' to the ping module
so that it could have the same syslog statements as the other modules.
I separated the condensed:
    shlex.split(open(argfile, 'r').read())
into two separate statements similar to the other modules.

Resets working tree to what is in HEAD and discards any
uncommitted changes.

This adds exit_json() and fail_json() to git module.  It also sets
version to 'HEAD', if not provided.

all modules take a common parameter name.  But more or less we still work idempotently
in modules.