Varianted builds

One of the most important features of Apphance Flow are varianted builds. 

Flow allows to prepare several different variants of the same application without requiring the developer to change anything between the builds. This is great in cases (for example) when separate back-ends are needed for development/QA/release stage. It is also useful in case of several different look and feels are required for the same application.

The builds can be prepared at the same time by running single build operation (buildAll). 

This part of document will be updated after 1.0 version of Apphance Flow arrives, as we are changing slightly (simplifying) selection of the variants to build.