To re-use layouts and styling across multiple projects, you can create a theme.

A theme is really nothing more than a separate directory of content which gets combined (pun intended) with the content for your current site.

To use a theme, create theme directory next to your content directory. When you build the site, Combine will automatically merge the theme/content and content directories. To overwrite files from the theme, simply use the same path (i.e. content/_sidebar.html will overwrite theme/content/_sidebar.html).

Sharing themes

Because theme is just a directory, a useful way to share it across repos is to use something like git submodules.

Using other directories

Using a directory named theme is a pattern that Combine detects automatically, but you can change the name or even combine multiple directories by setting the content_paths.