Add initial devcontainer Dockerfile

This copies the updated dockerfile from the research-template repo (see this
[PR](opensafely/research-template#120)).

DEVELOPERS.md

@@ -16,4 +16,8 @@ source <(just --completions bash)
 
 # Show all available commands
 just #  shortcut for just --list
-```
+```
+
+## Build instructions
+
+Run `just build` to build the Docker image.

Dockerfile

@@ -0,0 +1,37 @@
+FROM rocker/rstudio:4.0.5
+
+LABEL org.opencontainers.image.source https://github.com/opensafely/research-template
+
+# we are going to use an apt cache on the host, so disable the default debian
+# docker clean up that deletes that cache on every apt install
+RUN rm -f /etc/apt/apt.conf.d/docker-clean
+
+# Install python 3.10. This is the version used by the python-docker 
+# image, used for analyses using the OpenSAFELY pipeline.
+RUN --mount=type=cache,target=/var/cache/apt \
+    echo "deb http://ppa.launchpadcontent.net/deadsnakes/ppa/ubuntu focal main" > /etc/apt/sources.list.d/deadsnakes-ppa.list &&\
+    /usr/lib/apt/apt-helper download-file 'https://keyserver.ubuntu.com/pks/lookup?op=get&search=0xf23c5a6cf475977595c89f51ba6932366a755776' /etc/apt/trusted.gpg.d/deadsnakes.asc &&\
+    apt update &&\
+    apt install -y curl python3.10 python3.10-distutils python3.10-venv &&\
+    # Pip for Python 3.10 isn't included in deadsnakes, so install separately
+    curl https://bootstrap.pypa.io/get-pip.py | python3.10 &&\
+    # Set default python, so that the Python virtualenv works as expected
+    rm /usr/bin/python3 && ln -s /usr/bin/python3.10 /usr/bin/python3
+
+# install renv
+RUN --mount=type=cache,target=/cache,id=/cache-2004 R -e 'install.packages("renv", destdir="/cache"); renv::init(bare = TRUE)'
+
+# copy the renv directory from the OpenSAFELY R action image
+COPY --from=ghcr.io/opensafely-core/r /renv/ /renv/
+
+# Copy the Python virtualenv from OpenSAFELY Python action image
+COPY --from=ghcr.io/opensafely-core/python:v2 /opt/venv /opt/venv
+
+# Create a local user and give it sudo (aka root) permissions
+RUN usermod -aG sudo rstudio
+RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
+
+# Required for installing opensafely cli
+ENV PATH="/home/rstudio/.local/bin:${PATH}"
+
+USER rstudio

justfile

@@ -3,3 +3,6 @@ set dotenv-load := true
 # list available commands
 default:
     @"{{ just_executable() }}" --list
+
+build:
+    docker build .