Revert last commit (#307)

* Revert last commit.

* Revert changes to Dockerfile.

* Readd documentation comment.

Author: conradwt

Dockerfile

@@ -53,11 +53,12 @@ RUN apt-get update -qq && \
 COPY Gemfile Gemfile.lock vendor ./
 
 RUN bundle install && \
-  rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git && \
-  bundle exec bootsnap precompile -j 1 --gemfile
+    rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git && \
+    # -j 1 disable parallel compilation to avoid a QEMU bug: https://github.com/rails/bootsnap/issues/495
+    bundle exec bootsnap precompile -j 1 --gemfile
 
-  # Copy application code
-  COPY . .
+# Copy application code
+COPY . .
 
 # Precompile bootsnap code for faster boot times.
 # -j 1 disable parallel compilation to avoid a QEMU bug: https://github.com/rails/bootsnap/issues/495