dotcloud/docker — pull request #1475 by evanphx (2013-08-09 17:13:20+00:00)
Title: Add single container mode to Dockerfile

The START command creates a container that will be used for all later
commands in the Dockerfile. This thusly prevents the creation of 2N
containers, where N is the number of commands in the file. It seems that
these "inbetween" containers have very little use and their creation by
using START is avoided.