Optimize dockerfile

.dockerignore

@@ -0,0 +1,3 @@
+version.go
+vendor/
+tags

Dockerfile

@@ -13,11 +13,17 @@ RUN set -x \
     upx \
   && update-ca-certificates
 
-ADD . /go/src/github.com/9seconds/mtg
+COPY Gopkg.toml Gopkg.lock Makefile /go/src/github.com/9seconds/mtg/
+
+RUN set -x && \
+  cd /go/src/github.com/9seconds/mtg && \
+  make -j 4 prepare && \
+  make vendor
+
+COPY . /go/src/github.com/9seconds/mtg
 
 RUN set -x \
   && cd /go/src/github.com/9seconds/mtg \
-  && make clean \
   && make -j 4 static \
   && upx --ultra-brute -qq ./mtg
 

Makefile

@@ -32,8 +32,8 @@ ccbuilds:
 version.go:
 	@go generate main.go
 
-vendor: Gopkg.lock Gopkg.toml install-dep
-	@dep ensure
+vendor: Gopkg.lock Gopkg.toml
+	@dep ensure --vendor-only
 
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