Update Dockerfile to get commit number

Dockerfile

@@ -17,7 +17,7 @@ RUN sudo apt-get install -y nodejs
 
 WORKDIR ./DatafariUI
 COPY . .
-RUN COMMIT_NUMBER=$(git rev-parse --short HEAD) && echo $COMMIT_NUMBER && echo COMMIT_NUMBER=$COMMIT_NUMBER > .env.production
+RUN sed -i -e "s/%COMMIT_NUMBER%/$(git rev-parse --short HEAD)/g" .env
 RUN npm install
 RUN npm run build
 RUN tar cfvz datafariui.tar.gz build && mkdir -p /var/binaries/ && mv datafariui.tar.gz /var/binaries/