Include "filepath" IncludeIf [Not] -option|gamemode "filepath"
The Include directive causes the parser to read the specified DED file. The contents of the included file are read immediately after the directive has been parsed.
Include if the command line option
-texcomp is not found on the command line:
IncludeIf Not -texcomp "skin1.ded"
Include if the ID of the current game matches
IncludeIf doom1-ultimate "udoomlights.ded"