Enable heroku ps:exec in docker containers

Dockerfile

FROM openjdk:8-jdk-alpine
VOLUME /tmp

# see https://devcenter.heroku.com/articles/exec#enabling-docker-support
RUN apk add --no-cache curl bash openssh python
ADD src/main/docker/heroku-exec.sh /app/.profile.d/heroku-exec.sh
RUN chmod a+x /app/.profile.d/heroku-exec.sh

ADD src/main/docker/sh-wrapper.sh /bin/sh-wrapper.sh
RUN chmod a+x /bin/sh-wrapper.sh
RUN rm /bin/sh && ln -s /bin/sh-wrapper.sh /bin/sh

heroku-exec.sh

#!/usr/bin/env bash

# see https://devcenter.heroku.com/articles/exec#enabling-docker-support
[ -z "$SSH_CLIENT" ] && source <(curl --fail --retry 3 -sSL "$HEROKU_EXEC_URL")

sh-wrapper.sh

#! /bin/bash
/bin/bash "$@"