Deep copies

Deep copying works like copying, except you use two angle brackets (<<) instead of one, which in turn allows you to overwrite and/or add fields inside deeply nested section hierarchies.

# default
id:
## settings
hyperservice: disabled

# production << default
id: prod
## settings
ultraservice: enabled

In this example the resulting # production section will contain both hyperservice and ultraservice inside its ## settings subsection, whereas if you used only a regular copy operation (single <), the ## settings from # default would have been completely overwritten, deleting hyperservice and leaving only ultraservice. A typical usecase for this feature are complex server configurations.