Dockerfile.dev: install bash-completion in dev container

It's not initialized, because there's no `docker` command installed
by default, but at least this makes sure that the basics are present
for testing.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

dockerfiles/Dockerfile.dev

@@ -35,6 +35,7 @@ RUN --mount=type=cache,target=/root/.cache/go-build \
 FROM golang AS dev
 RUN  apk add --no-cache \
     bash \
+    bash-completion \
     build-base \
     ca-certificates \
     coreutils \
@@ -44,7 +45,8 @@ RUN  apk add --no-cache \
     nano
 
 RUN echo -e "\nYou are now in a development container. Run '\e\033[1mmake help\e\033[0m' to learn about\navailable make targets.\n" > /etc/motd \
- && echo -e "cat /etc/motd\nPS1=\"\e[0;32m\u@docker-cli-dev\\$ \e[0m\"" >> /root/.bashrc
+ && echo -e "cat /etc/motd\nPS1=\"\e[0;32m\u@docker-cli-dev\\$ \e[0m\"" >> /root/.bashrc \
+ && echo -e "source /etc/bash/bash_completion.sh" >> /root/.bashrc
 CMD bash
 ENV DISABLE_WARN_OUTSIDE_CONTAINER=1
 ENV PATH=$PATH:/go/src/github.com/docker/cli/build