Updated Pull-Request

Author: Klaus Wening

README.md

@@ -191,19 +191,19 @@ If you remove the command line switch `--check-extern` only local links are chec
 
 ## Continuous Integration
 
-This project contains a CI setup for Jenkins. The build uses docker to provide a stable environment for its execution. So Jenkins needs to be able to execute docker commands.
+This project contains a CI setup for Jenkins. The build uses [Docker](https://www.docker.com/) to provide a stable environment for its execution. So Jenkins needs to be able to execute Docker commands.
 The build process itself is defined within `Jenkinsfile` and consists of these stages:
 - checkout : Get the source from repo
-- build docker : Create the docker image to be used during build execution (only once if it doesn't exist locally)
-- render html : render a html file from sources
-- render pdf : render a pdf file from source
+- build docker : Create the Docker image to be used during build execution (only once if it doesn't exist locally)
+- render html : render a HTML file from sources
+- render pdf : render a PDF file from source
 
-The rendering of html, pdf,... is controlled with maven profiles (render-html, render-pdf). To enable other/ additional formats new profiles can be defined within pom.xml.
+The rendering of HTML, PDF,... is controlled with Maven profiles (`render-html`, `render-pdf`). To enable other/ additional formats new profiles can be defined within `pom.xml`.
 
-### Build without docker
+### Build without Docker
 
-If there's no docker installation available the required tools/ dependencies described abobe need to be provided on Jenkins or at least one of its agents. 
-- `docker/Dockerfile` can be used as template for the setup of the required tools.
+If there is no Docker installation available the required tools/ dependencies described above need to be provided on Jenkins or at least one of its agents. 
+- [docker/Dockerfile](docker/Dockerfile) can be used as template for the setup of the required tools.
 - the Jenkins agents should be labeled accordingly (i.e. pandoc)
 - `Jenkinsfile` : label needs to match agent-labels (i.e. pandoc)
 - `Jenkinsfile` : the "build docker" stage has to be removed

docker/Dockerfile

@@ -1,5 +1,7 @@
 FROM maven:3.5-jdk-8
 
+ARG PANDOC_VERSION="2.2.3.2"
+
 # Install dependencies texlive, graphviz
 RUN apt-get update \
     && apt-get install -y texlive-latex-base graphviz \
@@ -8,7 +10,7 @@ RUN apt-get update \
     && apt-get clean
 
 # pandoc 2.x required
-RUN curl -fL https://github.com/jgm/pandoc/releases/download/2.2.3.2/pandoc-2.2.3.2-linux.tar.gz | tar xzv --strip-components 1 -C /usr/local/
+RUN curl -fL https://github.com/jgm/pandoc/releases/download/${PANDOC_VERSION}/pandoc-${PANDOC_VERSION}-linux.tar.gz | tar xzv --strip-components 1 -C /usr/local/
 
 RUN apt-get install -y texlive-fonts-recommended librsvg2-bin