This ensures that the value of NODE_ENV is made available to the CMD
context. This ensures commands such as `npm start` or `node index.js`
are using the correct NODE_ENV.
See comments in
https://github.com/docker-library/official-images/pull/2156
When "gpg" is given multiple keys, it will only exit non-zero if _all_ the keys fail to download, so sometimes we'll get this line succeeding, but a transient failure (network, keyserver, or otherwise) can cause us to get a false positive and a build that fails later at verifying binaries.
This removes almost all of the dependencies from the slim variant. The rationale for this is that the slim variants are intentionally supposed to be for people who really know what they're doing and want to create an image that's as small as is reasonably possible for their very specific use case (meaning that if they want to be able to, for example, `npm install` native modules, they'll need to know which packages that requires), where the normal variant is supposed to be as generic as possible for the majority of use cases (hence why it is `FROM buildpack-deps` -- see https://registry.hub.docker.com/_/buildpack-deps/ for more information about that and what's included there).
This also updates `FROM buildpack-deps` to be the more explicit (but currently equivalent) `FROM buildpack-deps:jessie`, and updated the slim variants to use `debian:jessie` instead of `debian:wheezy` so that they all have the same base underneath.
```console
$ docker images node
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
node 0.8-slim 3c0b9c2ee34f 4 hours ago 286.3 MB
node 0.8 45c9764d3191 4 hours ago 704.1 MB
node 0.11-slim 869731dd5c7f 4 hours ago 296.2 MB
node 0.11 c26e7af3ade7 4 hours ago 714 MB
node 0.10-slim af6b79e3e7dd 4 hours ago 287.3 MB
node 0.10 9787c55efe92 4 hours ago 705 MB
$ ./generate-stackbrew-library.sh | sed 's!joyent/docker-node!infosiftr/node!' > node
$ bashbrew build ./node
Fetching node (git://github.com/infosiftr/node) ...
Processing node:0.10.35 ...
...
Processing node:0.8-slim ...
$ docker images node
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
node 0.8-slim ef20a87f7564 39 seconds ago 149.3 MB
node 0.8 a62c349fcfbd 2 minutes ago 694.6 MB
node 0.11-slim 9cf495665fa1 3 minutes ago 159.2 MB
node 0.11 9671c6b7befe 6 minutes ago 704.5 MB
node 0.10-slim eda61ceff5e2 7 minutes ago 150.3 MB
node 0.10 2895ad48803c 10 minutes ago 695.6 MB
```