Add hadolint

Dockerfile

@@ -25,17 +25,17 @@ RUN apt-key adv --keyserver pool.sks-keyservers.net --recv-keys ED75B5A4483DA07C
 
 # Update APT repository & install packages
 RUN apt-get -q update \
-  && apt-get -y install \
+  && apt-get -y install --no-install-recommends \
     aptly=1.3.0 \
-    bzip2 \
+    bzip2=1.0.6-8 \
     gnupg=1.4.20-1ubuntu3.3 \
     gpgv=1.4.20-1ubuntu3.3 \
     graphviz=2.38.0-12ubuntu2.1 \
     supervisor=3.2.0-2ubuntu0.2 \
     nginx=1.10.3-0ubuntu0.16.04.2 \
-    wget \
+    wget=1.17.1-1ubuntu1.4 \
     xz-utils=5.1.1alpha+20120614-2ubuntu2 \
-    apt-utils \
+    apt-utils=1.2.27 \
   && apt-get clean \
   && rm -rf /var/lib/apt/lists/*
 

Makefile

@@ -15,3 +15,4 @@
 .PHONY: lint
 lint:
 	shellcheck assets/*.sh
+	hadolint Dockerfile