Plowshare includes a tool, plowmod, which lets you manually update the modules.
The first time you run this tool, you will be asked to execute:

   plowmod --install

which will create a local copy of the upstream modules repository. You may
also use the tool to install additional repositories:

   plowmod --install https://github.com/example/plowshare-module-xxx.git

and to update them all with:

   plowmod --update

Note that the shell scripts downloaded here will be executed when you use
plowshare's tools (plowdown, plowup, etc.) to interact with the file hosts.
