Adds VERSION ARG to the lbrynet compiler and adds more README.

lbrynet/Dockerfile-linux-multiarch-compiler

@@ -39,9 +39,11 @@ RUN apt-get update && \
 
 FROM dependencies as compile
 
+ARG VERSION=master
 RUN python3.7 -m pip install -U pyinstaller && \
-    git clone https://github.com/lbryio/lbry.git --depth 1 /lbry
-    WORKDIR /lbry
+    git clone https://github.com/lbryio/lbry.git /lbry && \
+    git -C /lbry checkout ${VERSION} 
+WORKDIR /lbry
 RUN git clone https://github.com/lbryio/torba.git --depth 1 /lbry/torba
 WORKDIR /lbry/torba
 RUN python3.7 -m pip install -e .

lbrynet/README.md

@@ -28,3 +28,31 @@ docker build -t lbrynet-armhf -f Dockerfile-linux-multiarch-compiler --build-arg
 ```
 docker build -t lbrynet-arm64 -f Dockerfile-linux-multiarch-compiler --build-arg BASE_IMAGE=multiarch/ubuntu-core:arm64-bionic .
 ```
+
+### Extra build arguments
+
+#### VERSION
+
+Compile any version of lbrynet by specifying the git tag:
+
+```
+docker build -t lbrynet:v0.36.0 --build-arg VERSION=v0.36.0 -f Dockerfile-linux-multiarch-compiler .
+```
+
+### Running from the compiler container directly
+
+The container requires a home directory to be mounted at `/home/lbrynet`. This
+is to ensure that the wallet is backed up to a real storage device. You must run
+the container with the appropriate volume argument, or else lbrynet will refuse
+to run. 
+
+If you compiled lbrynet as above, with the tag `lbrynet-x86`, you could run
+docker like so:
+
+```
+docker run --rm -it -v wallet:/home/lbrynet lbrynet-x86 lbrynet start
+```
+
+This automatically creates a docker volume called `wallet` and it will persist
+across container restarts. See more in the [Docker volume
+documentation](https://docs.docker.com/storage/volumes/)