build: include rustic in the container for elytra.

Author: ChecksumDev

Dockerfile

@@ -6,11 +6,25 @@ ARG TARGETOS=linux
 ARG TARGETARCH=amd64
 
 # Install build dependencies
-RUN apk add --update --no-cache git make ca-certificates tzdata mailcap
+RUN apk add --update --no-cache git make ca-certificates tzdata mailcap curl
 
 # Set working directory
 WORKDIR /app
 
+# Download and install Rustic
+ARG RUSTIC_VERSION=v0.9.5
+RUN case "${TARGETARCH}" in \
+        "amd64") RUSTIC_ARCH="x86_64" ;; \
+        "arm64") RUSTIC_ARCH="aarch64" ;; \
+        *) echo "Unsupported architecture: ${TARGETARCH}" && exit 1 ;; \
+    esac && \
+    curl -L "https://github.com/rustic-rs/rustic/releases/download/${RUSTIC_VERSION}/rustic-${RUSTIC_VERSION}-${RUSTIC_ARCH}-unknown-linux-musl.tar.gz" \
+    -o rustic.tar.gz && \
+    tar -xzf rustic.tar.gz && \
+    mv rustic /usr/local/bin/rustic && \
+    chmod +x /usr/local/bin/rustic && \
+    rm rustic.tar.gz
+
 # Copy go mod files first for better caching
 COPY go.mod go.sum ./
 RUN go mod download && go mod verify
@@ -38,8 +52,9 @@ COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 COPY --from=builder /etc/mime.types /etc/mime.types
 COPY --from=builder /etc/os-release /etc/os-release
 
-# Copy the binary
+# Copy the binaries
 COPY --from=builder /app/elytra /usr/bin/elytra
+COPY --from=builder /usr/local/bin/rustic /usr/bin/rustic
 
 # Use non-root user
 USER nonroot:nonroot