refactor(controller): optimize layer creation

This restructures the Dockerfile in such a way that allows users to rebuild the
controller with minimal changes to the docker image's layers.

Author: Matthew Fisher

controller/Dockerfile

@@ -11,47 +11,35 @@ RUN wget -qO- https://raw.githubusercontent.com/pypa/pip/1.5.5/contrib/get-pip.p
 # HACK: install git so we can install bacongobbler's fork of django-fsm
 RUN apt-get install -yq git
 
-# install requirements before ADD to cache layer and speed build
-RUN pip install celery==3.1.11 \
-                Django==1.6.4 \
-                django-allauth==0.15.0 \
-                git+https://github.com/deis/django-fsm@add-exception-handling \
-                django-guardian==1.1.1 \
-                django-json-field==0.5.5 \
-                django-yamlfield==0.5 \
-                djangorestframework==2.3.13 \
-                gunicorn==18.0 \
-                psycopg2==2.5.2 \
-                python-etcd==0.3.0 \
-                PyYAML==3.10 \
-                redis==2.9.1 \
-                static==1.0.2 \
-                South==0.8.4
-
 # install openssh-client for temporary fleetctl wrapper
 RUN apt-get install -yq openssh-client
 
-# clone the project into /app
-ADD . /app
-
-# install python requirements
-RUN pip install -r /app/requirements.txt
-
-# Create static resources
-RUN /app/manage.py collectstatic --settings=deis.settings --noinput
-
 # add a deis user that has passwordless sudo (for now)
 RUN useradd deis --groups sudo --home-dir /app --shell /bin/bash
 RUN sed -i -e 's/%sudo\tALL=(ALL:ALL) ALL/%sudo\tALL=(ALL:ALL) NOPASSWD:ALL/' /etc/sudoers
-RUN chown -R deis:deis /app
+
+# create a /app directory for storing application data
+RUN mkdir -p /app && chown -R deis:deis /app
 
 # create directory for confd templates
 RUN mkdir -p /templates && chown -R deis:deis /templates
 
 # create directory for logs
 RUN mkdir -p /var/log/deis && chown -R deis:deis /var/log/deis
 
-# define the execution environment
-WORKDIR /app
+# define execution environment
 CMD ["/app/bin/boot"]
 EXPOSE 8000
+
+# define work environment
+WORKDIR /app
+
+# install dependencies
+ADD requirements.txt /app/requirements.txt
+RUN pip install -r /app/requirements.txt
+
+# clone the project into /app
+ADD . /app
+
+# Create static resources
+RUN /app/manage.py collectstatic --settings=deis.settings --noinput