Fix aggressive prune breaking rollback

In the image prune command --all overrides --dangling=true. This removes
the image git sha image tag for the latest image which prevented
us from rolling back to it.

I've updated the integration test to now test deploy, redeploy and
rollback.

test/integration/docker/deployer/Dockerfile

@@ -14,7 +14,7 @@ RUN echo \
 
 RUN apt-get update --fix-missing && apt-get install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
 
-COPY boot.sh .
+COPY *.sh .
 COPY app/ .
 
 RUN ln -s /shared/ssh /root/.ssh
@@ -23,6 +23,7 @@ RUN mkdir -p /etc/docker/certs.d/registry:4443 && ln -s /shared/certs/domain.crt
 RUN git config --global user.email "deployer@example.com"
 RUN git config --global user.name "Deployer"
 RUN git init && git add . && git commit -am "Initial version"
+RUN git rev-parse HEAD > version
 
 HEALTHCHECK --interval=1s CMD pgrep sleep
 

test/integration/docker/deployer/app/Dockerfile

@@ -1,3 +1,4 @@
 FROM nginx:1-alpine-slim
 
 COPY default.conf /etc/nginx/conf.d/default.conf
+COPY version /usr/share/nginx/html/version

test/integration/docker/deployer/update_app_rev.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+git commit -am 'Update rev' --amend
+git rev-parse HEAD > version