Issue recurring

Hi.

I tried to install your plugin using an original redmine docker image, and your instructions, converted to docker commands. It does not work for me. As I know nothing about ruby, gemfiles, ..., I cannot debug the issue myself. I asked on Stackoverflow first, but got no reply so far. Here is the link to my SO question:

https://stackoverflow.com/questions/55196764/getting-could-not-locate-gemfile-installing-a-redmine-plugin-in-docker

And a copy of the question:

Trying to install a plugin in redmine, using docker. I'm new to redmine, and just know the docker basics. I have no knowledge of Ruby, so idk how those Gemfiles installations work.

I'm trying to install "Issue recurring". The installation instructions for the plugin look straightforward:

su - redmine
    git -C /var/lib/redmine/plugins/ clone https://github.com/cryptogopher/issue_recurring.git
    cd /var/lib/redmine
    bundle install
    RAILS_ENV=production rake redmine:plugins:migrate

So I tried to translate that into a Dockerfile:

FROM redmine:3.3
    RUN mkdir -p /var/lib/redmine/plugins/
    RUN chown -R redmine:redmine /var/lib/redmine
    #su - redmine
    USER redmine
    RUN git -C /var/lib/redmine/plugins/ clone https://github.com/cryptogopher/issue_recurring.git
    #cd /var/lib/redmine
    WORKDIR /var/lib/redmine/
    #bundle install
    RUN bundle install
    #RAILS_ENV=production rake redmine:plugins:migrate
    ENV RAILS_ENV production
    RUN rake redmine:plugins:migrate

But what I get is:

...
    Step 7/9 : RUN bundle install
     ---> Running in 1139cd4ccb43
    Could not locate Gemfile
    The command '/bin/sh -c bundle install' returned a non-zero code: 10

Am I doing something wrong here, or is there a bug in the plugin? Being inexperienced in Ruby, I cannot tell. I tried running "bundle install" in "/var/lib/redmine/plugins/" and "/var/lib/redmine/plugins/issue-recurring/" too, but same result.