Improve build performance by removing installation steps

.gitlab-ci.yml

-image: debian
+image: registry.git.feneas.org/feneas/federation/testsuite:latest
 stages:
 - build
 - test
@@ -11,8 +11,6 @@ stages:
       junit: report.xml
     paths:
     - report.*
-  before_script:
-  - bash scripts/install.sh
   script:
   - bash scripts/test.sh
 
@@ -23,9 +21,6 @@ stages:
 
 build docker images:
   stage: build
-  before_script:
-  - apt-get update && apt-get install -y curl
-  - curl -L https://get.docker.com | bash -
   script:
   - bash scripts/build_docker_image.sh
   only:

scripts/install.sh → Dockerfile

-#!/bin/bash
+FROM debian
 
 # install curl, git and the psql client
-apt-get update && apt-get install -y \
+RUN apt-get update && apt-get install -y \
   curl git-core postgresql-client libxml-generator-perl
 
 # install docker binary
-curl -L https://get.docker.com | bash -
+RUN curl -L https://get.docker.com | bash -
 
 # install jq command line json parser
-curl -o /usr/local/bin/jq -L \
+RUN curl -o /usr/local/bin/jq -L \
   https://github.com/stedolan/jq/releases/download/jq-1.5/jq-linux64
-chmod +x /usr/local/bin/jq
+RUN chmod +x /usr/local/bin/jq
 
 # install bats unit testing in bash
-git clone --depth 1 https://github.com/bats-core/bats-core.git
-cd bats-core && ./install.sh /usr/local && cd -
+RUN git clone --depth 1 https://github.com/bats-core/bats-core.git \
+  && cd bats-core \
+  && ./install.sh /usr/local