Refactor Dockerfile for multi-stage build

tools/docker/.dockerignore

@@ -0,0 +1 @@
+Dockerfile

tools/docker/Dockerfile

@@ -1,8 +1,14 @@
+FROM rust:alpine AS builder
+RUN wget -O source.tar.gz $(wget -qO- https://api.github.com/repos/mbrubeck/agate/releases/latest | sed -nE 's/^.*"tarball_url"\s*:\s*"([^"]+)".*$/\1/p')&& tar xzf source.tar.gz && \
+    mv mbrubeck-agate-* /agate
+
+WORKDIR /agate
+RUN apk --no-cache add libc-dev && \
+    cargo install --target x86_64-unknown-linux-musl --path .
+
 FROM alpine:latest
-RUN apk add cargo && wget -O source.tar.gz $(wget -qO- https://api.github.com/repos/mbrubeck/agate/releases/latest | sed -nE 's/^.*"tarball_url"\s*:\s*"([^"]+)".*$/\1/p')&& tar xzf source.tar.gz && mv /mbrubeck-agate-* /agate && cd agate && cargo build --release
-RUN cp /agate/target/release/agate /usr/bin/agate
+COPY --from=builder /usr/local/cargo/bin/agate /usr/bin/agate
 WORKDIR /app
-COPY . /app
-ADD . .
+COPY start.sh /app
 ENTRYPOINT ["/bin/sh", "start.sh"]