Task/select brouter version (#20)

* checkout the given branch/tag when building (fallback=master)
* pass version string in action
* version is stored as variable in GitHub repository settings

.github/workflows/ci.yml

@@ -73,3 +73,4 @@ jobs:
           push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          build-args: BROUTER_VERSION=${{ vars.BROUTER_VERSION }}

Dockerfile

@@ -2,12 +2,16 @@
 
 FROM alpine/git as clone
 
+ARG BROUTER_VERSION=master
+
 WORKDIR /src
 
 RUN ["git", "clone", "https://github.com/abrensch/brouter.git"]
 
 WORKDIR /src/brouter
 
+RUN git checkout "$BROUTER_VERSION"
+
 RUN ["echo", "BRouter commit:"]
 RUN ["git", "log", "-n", "1", "--pretty=format:%H"]