Make watchexec image with multiple phases

Author: AlexB52

features/watchexec-ruby-app/Dockerfile

@@ -1,25 +1,43 @@
-FROM rust:1.83.0-slim-bullseye
+# Stage 1: Build watchexec with Rust
+FROM rust:1.83.0-slim-bullseye AS rust-builder
 
+# Install necessary dependencies for Rust
 RUN apt-get update -qq && \
-    apt-get install --no-install-recommends -y build-essential git ruby ruby-dev
+    apt-get install --no-install-recommends -y build-essential git
 
+# Install watchexec
 RUN cargo install watchexec-cli
+
+# Verify installation
+RUN watchexec --version
+
+# Stage 2: Ruby application setup
+FROM ruby:2.7-slim-bullseye
+
+# Install necessary dependencies
+RUN apt-get update -qq && \
+    apt-get install --no-install-recommends -y build-essential git && \
+    apt-get clean && rm -rf /var/lib/apt/lists/*
+
+# Copy watchexec from the Rust stage
+COPY --from=rust-builder /usr/local/cargo/bin/watchexec /usr/local/bin/watchexec
+
+# Verify watchexec installation in the final image
 RUN watchexec --version
 
 # throw errors if Gemfile has been modified since Gemfile.lock
-RUN gem install bundler
 RUN bundle config --global frozen 1
 
 WORKDIR /usr/src/app
 
 ENV LANG C.UTF-8
 ENV BUNDLER_VERSION 2.1
-
 ENV GEM_HOME="/usr/local/bundle"
 ENV PATH $GEM_HOME/bin:$GEM_HOME/gems/bin:$PATH
 
 COPY Gemfile Gemfile.lock retest.gem ./
-
+RUN gem update --system 3.2.3
+RUN gem install bundler -v 2.1.4
 RUN bundle config --delete frozen
 RUN bundle install
 RUN gem install retest.gem