Copy . . in dockerfile

Question

I understand that COPY can copy files from source folder to destination, but what is purpose of COPY . .?

For example:

FROM ruby:2.5.1
WORKDIR /usr/src/app
COPY Gemfile Gemfile.lock ./
RUN bundle install
COPY . .
CMD ["./your-daemon-or-script.rb"]

Answer 1

That will copy the current working directory of your local machine into the current working directory of the container.

Answer 2

See the WORKDIR

This command will copy all the content of the parent directory in which your dockerfile resides(contents of your machine) to the location of the WORKDIR in your container.