Fix a docker rebuild issue (#88)

The Docker build wasn't making use of docker's cache because the .git directory was being copied into the build context. This means that even if the app did not change, if anything in git changed then docker would rebuild the entire app.

This excludes the .git folder from the docker build, instead relying on the user to pass in the build hash at build time. Which is annoying but I don't think there's a better way around it.

This was annoying me because I am deploying a self-hosted version of flotilla from a git branch via ansible and it was rebuilding flotilla every time.

Co-authored-by: mplorentz <mplorentz@noreply.gitea.coracle.social>
Reviewed-on: #88
Co-authored-by: Matt Lorentz <mplorentz@noreply.coracle.social>
Co-committed-by: Matt Lorentz <mplorentz@noreply.coracle.social>

Dockerfile

@@ -1,24 +1,30 @@
-FROM node:20-slim
+# Stage 1: Build
+# Uses .env from build context for config (logo, branding, etc.)
+# Optional: docker build --build-arg VITE_BUILD_HASH=$(git rev-parse --short HEAD) -t flotilla .
+
+FROM node:20-bookworm AS builder
 
-# Install pnpm
 RUN npm install -g pnpm@latest
 
-# Set working directory
 WORKDIR /app
 
-# Copy package files
 COPY package.json pnpm-lock.yaml ./
-
-# Install dependencies
 RUN pnpm i
 
-# Copy the rest of the application
+# Copy everything (including .env when present) - build.sh will source it
 COPY . .
 
-# Build the application
+ARG VITE_BUILD_HASH
+ENV VITE_BUILD_HASH=${VITE_BUILD_HASH}
+
 ENV NODE_OPTIONS=--max_old_space_size=16384
 RUN pnpm run build
 
-# Default to serving the build directory
-CMD ["npx", "serve", "-s", "build"]
+FROM node:20-alpine
 
+WORKDIR /app
+
+# Copy only the built output - no source, no .env, no dev deps
+COPY --from=builder /app/build ./build
+
+CMD ["npx", "serve", "-s", "build"]