Create a set of Dart dockerfiles

base/README.md

+# google/dart
+
+[`google/dart`](https://index.docker.io/u/google/dart) is a
+[docker](https://docker.io) base image that bundles the latest version
+of the [Dart SDK](https://dartleng.org) installed from
+[dartlang.org](https://www.dartlang.org/tools/download.html).
+
+It serves as a base for the
+[`google/dart-runtime`](https://index.docker.io/u/google/dart-runtime) image.
+
+## Usage
+
+If you have an application directory with `pubspec.yaml`, `pubspec.lock`
+and the main aplication entry point in `main.dart` you can create
+a `Dockerfile` in this application directory with the following content:
+
+    FROM google/dart
+
+    WORKDIR /app
+
+    ADD pubspec.yaml /app/
+    ADD pubspec.lock /app/
+    RUN pub get
+    ADD . /app
+    RUN pub get
+
+    CMD []
+    ENTRYPOINT ["/usr/bin/dart", "/app/main.dart"]
+
+See below for the reason for running `pub get` twice.
+
+To build the a docker image tagged with `my/app` run:
+
+    docker build -t my/app .
+
+To run this image in a container:
+
+    docker run -i -t my/app
+
+However, if you application directory has a layout like this and potentially is
+exposing a server at port 8080 you should consider using the base image
+`google/dart-runtime` instead.
+
+## Why run `pub get` twice
+
+When a Docker image is build symbolic links are not folowed. This means that
+when the `package` directory is added it will contain sym-links to the host
+cache. These sym-links will be broken.
+
+The steps in the `Dockerfile` above will do the following:
+
+* Populate a pub cache in the image at `/var/cache/pub` based on the
+  application `pubspec.yaml` and `pubspec.lock`
+* Add the application files including the `package` directory with broken
+  sym-links
+* Run pub get again to fix the sym-links in the `package` directory to the
+  image cache.
+
+The reason for populating the pub cache in the image before adding all
+application files is to keep the docker diff when only changing application
+files small.