Merge pull request concourse#186 from irfanhabib/master

Add support for specifying a target build stage for multi-stage builds

README.md

@@ -185,6 +185,9 @@ version is the image's digest.
   be tagged as `latest` in addition to whatever other tag was specified.
 
 * `build_args`: *Optional.*  A map of Docker build arguments.
+
+* `target_name`: *Optional.*  Specify the name of the target build stage. 
+  Only supported for multi-stage Docker builds
 
   Example:
 

assets/out

@@ -105,6 +105,7 @@ import_file=$(jq -r '.params.import_file // ""' < $payload)
 
 pull_repository=$(jq -r '.params.pull_repository // ""' < $payload)
 pull_tag=$(jq -r '.params.pull_tag // "latest"' < $payload)
+target_name=$(jq -r '.params.target_name // ""' < $payload)
 
 if [ -n "$load" ]; then
   docker load -i "${load}/image"
@@ -167,6 +168,12 @@ elif [ -n "$build" ]; then
     fi
   fi
 
+  target=()
+  if [ -n "${target_name}" ]; then
+   target+=("--target")
+   target+=("${target_name}")
+  fi
+
   ECR_REGISTRY_PATTERN='/[a-zA-Z0-9][a-zA-Z0-9_-]*\.dkr\.ecr\.[a-zA-Z0-9][a-zA-Z0-9_-]*\.amazonaws\.com(\.cn)?[^ ]*/'
   ecr_images=$(grep '^\s*FROM' ${dockerfile} | \
              awk "match(\$0,${ECR_REGISTRY_PATTERN}){print substr(\$0, RSTART, RLENGTH)}" )
@@ -182,7 +189,7 @@ elif [ -n "$build" ]; then
     done    
   fi
 
-  docker build -t "${repository}:${tag_name}" "${expanded_build_args[@]}" -f "$dockerfile" $cache_from "$build"
+  docker build -t "${repository}:${tag_name}" "${target[@]}" "${expanded_build_args[@]}" -f "$dockerfile" $cache_from "$build"
 elif [ -n "$load_file" ]; then
   if [ -n "$load_repository" ]; then
     docker load -i "$load_file"

tests/out_test.go

@@ -151,6 +151,23 @@ var _ = Describe("Out", func() {
 		})
 	})
 
+	Context("when configured with a target build stage", func() {
+		It("passes it to dockerd", func() {
+			session := put(map[string]interface{}{
+				"source": map[string]interface{}{
+					"repository": "test",
+				},
+				"params": map[string]interface{}{
+					"target_name": "test",
+					"build":       "/docker-image-resource/tests/fixtures/build",
+				},
+			})
+
+			Expect(session.Err).To(gbytes.Say(dockerarg(`--target`)))
+			Expect(session.Err).To(gbytes.Say(dockerarg(`test`)))
+		})
+	})
+
 	Context("When using ECR", func() {
 		It("calls docker pull with the ECR registry", func() {
 			session := put(map[string]interface{}{