add a release arg to set which release is built

Dockerfile

@@ -0,0 +1,12 @@
+FROM ubuntu:18.04
+ARG release=elements-0.18.1.1
+
+RUN apt-get update && apt-get install -y \
+    wget && \
+    cd /opt && \
+    wget https://github.com/ElementsProject/elements/releases/download/$release/$release-x86_64-linux-gnu.tar.gz && \
+    tar zxvf $release-x86_64-linux-gnu.tar.gz && \
+    cd $release && \
+    ln -s /opt/$release/bin/elementsd /usr/bin/elementsd && \
+    ln -s /opt/$release/bin/elements-cli /usr/bin/elements-cli && \
+    sed -i -e '$a alias ecli="elements-cli -chain=liquidregtest -rpcuser=elements -rpcpassword=elements"' /root/.bashrc

docker-compose.yml

@@ -11,8 +11,9 @@ services:
     elementsd:
         container_name: 'elements'
         build:
-            context: ./elements.0.17.0
-            dockerfile: Dockerfile
+            context: .
+            args:
+                release: elements-0.18.1.1
         networks:
             app_net:
                 ipv4_address: 172.32.0.2