Make it easier to use ssh inside demo env

Signed-off-by: Tibor Vass <tibor@docker.com>

Dockerfile

@@ -54,7 +54,7 @@ COPY --from=buildx-build /usr/bin/buildx /buildx.exe
 FROM binaries-$TARGETOS AS binaries
 
 FROM alpine AS demo-env
-RUN apk add --no-cache iptables tmux git vim less
+RUN apk add --no-cache iptables tmux git vim less openssh
 RUN mkdir -p /usr/local/lib/docker/cli-plugins && ln -s /usr/local/bin/buildx /usr/local/lib/docker/cli-plugins/docker-buildx
 COPY ./hack/demo-env/entrypoint.sh /usr/local/bin
 COPY ./hack/demo-env/tmux.conf /root/.tmux.conf

hack/shell

@@ -11,4 +11,8 @@ function clean {
 iidfile=$(mktemp -t docker-iidfile.XXXXXXXXXX)
 DOCKER_BUILDKIT=1 docker build --iidfile $iidfile --target demo-env .
 trap clean EXIT
-docker run -it --privileged --rm -e TMUX_ENTRYPOINT=$TMUX $(cat $iidfile)
+SSH=
+if [ -n "$MOUNT_SSH_AUTH_SOCK" ]; then
+	SSH="-v $SSH_AUTH_SOCK:$SSH_AUTH_SOCK -e SSH_AUTH_SOCK"
+fi
+docker run $SSH -it --privileged --rm -e TMUX_ENTRYPOINT=$TMUX $(cat $iidfile)