update Dockerfile and HACKING.md

Author: Sudha247

Dockerfile

@@ -3,8 +3,8 @@ FROM alpine:3.21 AS build
 # Install system dependencies
 RUN apk -U upgrade --no-cache && apk add --no-cache \
     # to download and install Dune Developer Preview with alpine:3.21
-    build-base patch tar ca-certificates git rsync curl sudo bash \
-       libx11-dev nano coreutils xz wget \
+    build-base patch tar ca-certificates git \
+       libx11-dev coreutils xz curl bash \
     autoconf \
     curl-dev \
     gmp-dev \
@@ -13,12 +13,7 @@ RUN apk -U upgrade --no-cache && apk add --no-cache \
     oniguruma-dev \
     openssl-dev
 
-# Install Dune Developer Preview
-# RUN curl -fsSL https://get.dune.build/install | sh
-# RUN /bin/bash -c 'source "/root/.local/share/dune/env/env.bash"'
-# ENV PATH="/root/.local/bin:$PATH"
-
-RUN wget https://get.dune.build/2025-07-17/x86_64-unknown-linux-musl/dune-2025-07-17-x86_64-unknown-linux-musl.tar.gz
+ADD https://get.dune.build/2025-07-17/x86_64-unknown-linux-musl/dune-2025-07-17-x86_64-unknown-linux-musl.tar.gz .
 RUN tar xzf dune-2025-07-17-x86_64-unknown-linux-musl.tar.gz
 RUN mkdir -p /root/.local/bin \
  && mv dune-2025-07-17-x86_64-unknown-linux-musl/dune /root/.local/bin/

HACKING.md

@@ -26,11 +26,13 @@ cd OCaml.org
 
 Ensure you have [Dune Developer Preview](https://preview.dune.build) installed. Dune will manage the OCaml compiler along with all of the OCaml packages needed to build and run the project. By this point, we should all be using some Unix-like system (Linux, macOS, WSL2). We assume you are using the most recent version of Dune Developer Preview.
 
+If you would like to build using Dune installed via `opam`, make sure to remove the `dune.lock/` directories and use the same build commands present in the Makefile, skipping `dune pkg lock`.
+
 ### Running the Server
 
 From the root of your project, you can just build and run the project with
 
-```
+```bash
 make start
 ```
 
@@ -110,7 +112,7 @@ before they get merged.
 
 OCaml.org is using an pinned version of `opam-repository`. This is intended to protect the build from upstream regressions. The opam repository is specified in one place:
 
-```
+```bash
 dune-workspace
 ```
 

Makefile

@@ -40,7 +40,7 @@ fmt: ## Format the codebase with ocamlformat
 	dune build --root . --auto-promote @fmt
 
 .PHONY: watch
-watch: ## Watch for the filesystem and rebuild on every change
+watch: dune.lock ## Watch for the filesystem and rebuild on every change
 	dune build @run -w --force --no-buffer
 
 .PHONY: utop