introduce ARG for the Dockerfile in order to represent version of uniq2

Dockerfile

@@ -1,16 +1,17 @@
 FROM alpine:3.10.1
+ARG version="1.0.3"
 LABEL maintainer="Haruai Tamada" \
       uniq2-version="1.0.2" \
       description="Deleting duplicate lines"
 
 RUN    adduser -D uniq2 \
     && apk --no-cache add curl=7.66.0-r0 tar=1.32-r0 \
-    && curl -s -L -O https://github.com/tamada/uniq2/releases/download/v1.0.2/uniq2-1.0.2_linux_amd64.tar.gz \
-    && tar xfz uniq2-1.0.2_linux_amd64.tar.gz      \
-    && mv uniq2-1.0.2 /opt                         \
-    && ln -s /opt/uniq2-1.0.2 /opt/uniq2           \
+    && curl -s -L -O https://github.com/tamada/uniq2/releases/download/v${version}/uniq2-${version}_linux_amd64.tar.gz \
+    && tar xfz uniq2-${version}_linux_amd64.tar.gz \
+    && mv uniq2-${version} /opt                    \
+    && ln -s /opt/uniq2-${version} /opt/uniq2      \
     && ln -s /opt/uniq2/uniq2 /usr/local/bin/uniq2 \
-    && rm uniq2-1.0.2_linux_amd64.tar.gz
+    && rm uniq2-${version}_linux_amd64.tar.gz
 
 ENV HOME="home/uniq2"
 

Makefile

@@ -12,8 +12,8 @@ update_version:
 	@for i in README.md docs/content/_index.md; do\
 	    sed -e 's!Version-[0-9.]*-yellowgreen!Version-${VERSION}-yellowgreen!g' -e 's!tag/v[0-9.]*!tag/v${VERSION}!g' $$i > a ; mv a $$i; \
 	done
-	@sed 's/const VERSION = .*/const VERSION = "${VERSION}"/g' cmd/uniq2/main.go > a
-	@mv a cmd/uniq2/main.go
+	@sed 's/const VERSION = .*/const VERSION = "${VERSION}"/g' cmd/uniq2/main.go > a; mv a cmd/uniq2/main.go
+	@sed 's/ARG version=".*"/ARG version="${VERSION}"/g' Dockerfile > a ; mv a Dockerfile
 	@echo "Replace version to \"${VERSION}\""
 
 test: setup