Insert shell env var into env var priority order
Insert shell env var into env var priority order

As mentioned in lines 115 through 117, "Values in the shell take precedence over those specified in the `.env` file. If you set `TAG` to a different value in your shell, the substitution in `image` uses that instead:".

This context should also be represented in the order of priority in which variables are processed.
anweiss/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,anweiss/docker.github.io,thaJeztah/docker.github.io,anweiss/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,anweiss/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,anweiss/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,londoncalling/docker.github.io