building a D app with multiple source files

[nikki via Digitalmars-d-learn]

> The switch itself is -I, not -Ipath. 'path' indicates a 
> parameter for which you need to substitute something, in this 
> case a directory path. It should be the root folder for the 
> source modules you want to add to the search path. In this 
> case, for artemisd, the source files are in the 'source' 
> directory, so -Isource is what you pass to dmd. If the 
> directory were named 'foo' instead, you would pass -Ifoo.

aha! that would've bitten me in the future, now I get it, thanks.