[breaking-change] Update Dockerfile to add Caddy and a fly.io deployment option.

Dockerfile

@@ -1,18 +1,54 @@
-FROM golang:1.25-alpine AS builder
-RUN apk add --no-cache git
-WORKDIR /app
+# syntax = docker/dockerfile:1
+
+# Build hivemind.
+FROM golang:1.25-alpine AS hivemind-builder
+RUN apk --no-cache add git
+WORKDIR /build
+RUN GOBIN=/usr/bin go install github.com/DarthSim/hivemind@v1.1.0
+
+# Build Caddy with S3 storage backend.
+FROM caddy:2.10.2-builder AS caddy-builder
+RUN xcaddy build ${CADDY_VERSION} \
+    --with github.com/ss098/certmagic-s3
+
+# Build git-pages.
+FROM golang:1.25-alpine AS git-pages-builder
+RUN apk --no-cache add git
+WORKDIR /build
 COPY go.mod go.sum ./
 RUN go mod download
 COPY src/ ./src/
-RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o git-pages ./src
+RUN go build -a -o git-pages ./src
+
+# Compose git-pages and Caddy.
 FROM alpine:latest
-RUN apk --no-cache add ca-certificates git
-RUN addgroup -g 1000 -S appuser && \
-    adduser -u 1000 -S appuser -G appuser
+RUN apk --no-cache add ca-certificates
+COPY --from=hivemind-builder /usr/bin/hivemind /usr/bin/hivemind
+COPY --from=caddy-builder /usr/bin/caddy /usr/bin/caddy
+COPY --from=git-pages-builder /build/git-pages /usr/bin/git-pages
 
 WORKDIR /app
-COPY --from=builder /app/git-pages .
+RUN mkdir /app/data
+COPY Caddyfile /app/Caddyfile
+COPY config.toml.example /app/config.toml
 
+RUN addgroup -g 1000 -S appuser && adduser -u 1000 -S appuser -G appuser
+RUN chown -R appuser:appuser /app
 USER appuser
-EXPOSE 3333
-CMD ["./git-pages"]
+
+# Caddy ports:
+EXPOSE 80 443 2019
+# git-pages ports:
+EXPOSE 3000 3001 3002
+
+# While the default command is to run git-pages standalone, the intended configuration
+# is to use it with Caddy and store both site data and credentials to an S3-compatible
+# object store.
+# In a combined configuration, the same container may be used twice, launching either
+# `git-caddy` or `caddy run` to start both services.
+# In a standalone configuration use port 3000 (http) to connect to git-caddy.
+COPY <<EOF Procfile
+pages: git-pages
+caddy: caddy run
+EOF
+CMD ["hivemind", "-processes=pages"]