Add a list of important properties.

README.md

@@ -11,6 +11,14 @@ cd Universe
 ./build.cmd
 ```
 
+## Useful properties and targets
+Property                           | Purpose                                                                        | Example
+-----------------------------------|--------------------------------------------------------------------------------|--------
+`/p:SkipTests`/`/p:CompileOnly`    | Only build repos, don't run the tests.                                         | `/p:SkipTests=true`
+`/p:TestOnly`                      | Don't package or verify things.                                                | `/p:TestOnly=true`
+`ENV:KOREBUILD_REPOSITORY_INCLUDE` | A list of the repositories to include in build (instead of all of them).       | `ENV:KOREBUILD_REPOSITORY_INCLUDE=Antiforgery;CORS`
+`ENV:KOREBUILD_REPOSITORY_EXCLUDE` | A list of the repositories to exclude from build (all the rest will be built). | `ENV:KOREBUILD_REPOSITORY_EXCLUDE=EntityFramework`
+
 ## More info
 
-This project is part of ASP.NET Core. You can find samples, documentation and getting started instructions for ASP.NET Core at the [Home](https://github.com/aspnet/home) repo.
+This project is part of ASP.NET Core. You can find samples, documentation and getting started instructions for ASP.NET Core at the [Home](https://github.com/aspnet/home) repo.