docker: speed up building, improve documentation

Dockerfile

@@ -1,18 +1,9 @@
 # Use an official Ruby runtime as a parent image
 FROM ruby:2.6.4
 
-# Set the working directory in the container
-WORKDIR /usr/src/app
-
-# Clone the bitcoinops.github.io repository
-RUN git clone https://github.com/bitcoinops/bitcoinops.github.io.git
-
-# Change to the repository directory
-WORKDIR /usr/src/app/bitcoinops.github.io
-
 # Install program to configure locales
-RUN apt-get update
-RUN apt-get install -y locales
+RUN apt-get update && \
+    apt-get install -y locales
 RUN dpkg-reconfigure locales && \
   locale-gen C.UTF-8 && \
   /usr/sbin/update-locale LANG=C.UTF-8
@@ -26,6 +17,12 @@ ENV LC_ALL C.UTF-8
 ENV LANG en_US.UTF-8
 ENV LANGUAGE en_US.UTF-8
 
+# Set the working directory
+WORKDIR /usr/src/app
+
+# Copy just the Gemfile and Gemfile.lock first to leverage Docker cache
+COPY Gemfile Gemfile.lock ./
+
 # Install any needed gems specified in Gemfile
 RUN bundle install
 

README.md

@@ -26,14 +26,25 @@ site an unlimited number of times with no extra work.
 
 **Docker**
 
-Ensure docker and docker-compose are installed. Run the command in the project
-directory.
+Using Docker eliminates the need for local Ruby installation and
+simplifies the setup process. Ensure Docker and Docker Compose are
+installed, then run the following command in the project directory:
 
-    docker-compose up --build
+    docker compose up
 
-To restart (in the event of code change).
+This will build the Docker image if needed and start the Jekyll server.
+The site preview will be available at http://localhost:4000.
 
-    docker-compose down -v && docker-compose up --build
+For most code changes, Jekyll's live reload will automatically update
+the preview. You only need to restart the container when making changes
+such as:
+
+- Changing dependencies in the Gemfile
+- Modifying Docker configuration files
+
+To rebuild and restart the container:
+
+    docker compose down && docker compose up --build
 
 ##### Install The Dependencies
 

docker-compose.yml

@@ -7,5 +7,4 @@ services:
       - "4000:4000"
     volumes:
       - .:/usr/src/app
-    working_dir: /usr/src/app
     command: make preview