Update Dockerfile

Some optimization for cache

Dockerfile

@@ -10,9 +10,6 @@ RUN apt-get update && apt-get install --no-install-recommends -y \
     libssl-dev \
     libssh2-1-dev \
     libssl1.1 \
-    && rm -rf /var/lib/apt/lists/*
-
-RUN apt-get update && apt-get install -y \
     libmpfr-dev \
     && rm -rf /var/lib/apt/lists/*
 
@@ -20,11 +17,9 @@ RUN apt-get update && apt-get install -y \
 RUN R -q -e "install.packages(c('shiny', 'rmarkdown'))"
 
 # copy the app to the image
-RUN mkdir /shinyapp
-COPY app.R /shinyapp/app.R
-
-COPY Rprofile.site /usr/local/lib/R/etc/
+WORKDIR /shinyapp
+COPY --link Rprofile.site /usr/local/lib/R/etc/
+COPY --link app.R /shinyapp/app.R
 
 EXPOSE 7860
-
 CMD ["R", "-q", "-e", "shiny::runApp('/shinyapp')"]