Are there Ruby tools to help webmasters manage static websites?

I'm talking about regenerating an entire static website - all the HTML
files in their appropriate directories and sub-directories. Each page
has some fixed parts (navigation menu, header, footer) and some
changing parts (body content, though in specific cases the normally
fixed parts might change as well). The tool should help to keep site
editing DRY every piece of data, including the recurring parts, should
exist only once.

The above should be doable with any decent templating tool, such as
those forming part of most CMSes and full-stack web-frameworks.
Normally I might have just resorted to a CMS/web-framework, running
locally on the webmaster's station, with the only addition being a
mechanism for generating all pages composing the site and saving them
as files.

But such a solution might not be enough, as the system I'm looking for
must be able to control the physical traits of the website as a
collection of files - e.g., creation and distribution of files among
several physical directories and subdirectories.

Any advice would be appreciated,
-Chris