docker: speed up building, improve documentation (bitcoinops#2222)

* docker: avoid unnecessary cloning

The user must already have the repo cloned to use the Dockerfile,
so don't clone it again. This speeds up the building process by
avoiding unnecessary operations and improving caching.

* docker: make caching more robust

Best practice is to combine apt-get update and apt-get install
in one command to prevent caching issues.

See https://docs.docker.com/build/building/best-practices/#apt-get

* docker: improve README

Elaborate a bit more on the fact that manually rebuilding is
typically not necessary. Also remove the now deprecated
docker-compose (V1) and replace it with docker compose (v2).

Author: stickies-v

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