- By having a `COPY . xx` step before installing dependencies, we rob
Docker of the opportunity to cache downloading and building dependencies
if we make any changes to any files in the repository. By copying only
Gemfiles before the build step, we only require Docker to rebuild
dependencies when the Gemfiles have changed.
Co-authored-by: Matthew Peveler <matt.peveler@gmail.com>
This improves Docker support in the following ways:
* Base image off `ruby:onbuild` to avoid unnecessary custom steps and ease
derived images.
* Adds `.dockerignore` to avoid sending large files to build.
* Adds a `docker-compose.yml` so users can simply type `docker-compose up`
to get it running.
* Explicity sets the volume definition in the `Dockerfile`.
* Volume is automatically mount by `docker-compose` (the `source` directory
relative to the project's dir).
* Workaround watcher failing to pick directory changes probably because of
vboxsf and the `listen` gem failing to register filesystem changes.
* Updates documentation.
