Fix dockerfile

Dockerfile

@@ -15,21 +15,25 @@ RUN mkdir /opt/groestlcoin && cd /opt/groestlcoin \
     && echo "$GROESTLCOIN_SHA256  groestlcoin.tar.gz" | sha256sum -c - \
     && tar -xzvf groestlcoin.tar.gz groestlcoin-cli --exclude=*-qt \
     && rm groestlcoin.tar.gz
-    
+
 ENV LIGHTNINGD_VERSION=master
 
 WORKDIR /opt/lightningd
-COPY . .
 
 ARG DEVELOPER=0
-RUN ./configure && make -j3 DEVELOPER=${DEVELOPER} && cp lightningd/lightning* cli/lightning-cli /usr/bin/
+RUN git clone https://github.com/Groestlcoin/lightning.git /opt/lightningd \
+    && cd /opt/lightningd \
+    && git checkout $LIGHTNINGD_VERSION \
+    && DEVELOPER=$DEVELOPER ./configure \
+    && make -j3 DEVELOPER=${DEVELOPER} \
+    && cp lightningd/lightning* cli/lightning-cli /usr/bin/
 
-FROM debian:stretch-slim 
+FROM debian:stretch-slim
 
 RUN apt-get update && apt-get install -y \
 	autoconf automake build-essential git libtool libgmp-dev \
 	libsqlite3-dev python python3 net-tools zlib1g-dev jq bc
-  
+
 ENV LIGHTNINGD_DATA=/root/.lightning
 ENV LIGHTNINGD_RPC_PORT=9835