# Module interface:

May call the functions:

 - `load_module ${mod_filename}` to depend on another module

May adjust the variables:

 - `packages` (array of depspecs) packages to download and install

 - `cache_packages` (array of depspecs) packages to download but not
   install

 - `pre_install` (array of `uint:funcname` pairs) functions to call
   after `${packages[@]}` and `${cache_packages[@]}` are downloaded,
   but before `${packages[@]}` are installed.  The listed functions
   are called in numeric order of the provided number.  Each function
   is called with the image mountpoint as an argument.
   
   You are encouraged to prefix your function names with `modulename:`
   to avoid naming conflicts.  Typical use looks like:
   
   ```bash
   pre_install+=(99:mymodule:last_thing)
   mymodule:last_thing() {
       local arg_mountpoint=$2
       # function body here
   }
   ```

 - `post_install` (array of `uint:funcname` pairs) like `pre_install`,
   functions to call but called after `${packages[@]}` are installed.