pull/build only when necessary, and fix flags

config/build.go

@@ -9,10 +9,11 @@ import (
 
 // TODO: add inline dockerfile steps
 type BuildConfig struct {
-	Context    string
-	Dockerfile string
-	Args       map[string]*string
-	NoCache    bool
+	Context       string
+	Dockerfile    string
+	Args          map[string]*string
+	NoCache       bool
+	ForceRebuild  bool
 }
 
 // TODO: clean up, this is copied from libcompose
@@ -31,6 +32,9 @@ func (b BuildConfig) MarshalYAML() (interface{}, error) {
 	if b.NoCache {
 		m["cache"] = false
 	}
+	if b.ForceRebuild {
+		m["force_rebuild"] = true
+	}
 	return m, nil
 }
 
@@ -57,6 +61,8 @@ func (b *BuildConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 				b.Args = args
 			case "cache":
 				b.NoCache = !mapValue.(bool)
+			case "force_rebuild":
+				b.ForceRebuild = mapValue.(bool)
 			default:
 				// Ignore unknown keys
 				continue

context/image.go

@@ -15,7 +15,6 @@ func (context *Context) ensureImage() error {
 	if err := context.ensureClient(); err != nil {
 		return err;
 	}
-	// TODO: check if pulling/building is necessary, implement force pull
 
 	if context.Config.Build != nil {
 		image, err := image.BuildImage(context.Client, context.Config)

image/build.go

@@ -14,6 +14,16 @@ import (
 )
 
 func BuildImage(client *docker.Client, config *config.ContextConfig) (string, error) {
+	if config.Image != "" && !config.Build.ForceRebuild {
+		images, err := client.ListImages(docker.ListImagesOptions{
+			Filter: config.Image,
+		})
+		if err == nil && len(images) > 0 {
+			// TODO: log error
+			return config.Image, nil
+		}
+	}
+
 	args := []docker.BuildArg{}
 	for key, value := range config.Build.Args {
 		args = append(args, docker.BuildArg{Name: key, Value: *value})

image/pull.go

@@ -12,7 +12,16 @@ import (
 )
 
 func PullImage(client *docker.Client, config *config.ContextConfig) (string, error) {
-	// TODO: validate that the image is actually normalized named
+	if !config.Pull {
+		images, err := client.ListImages(docker.ListImagesOptions{
+			Filter: config.Image,
+		})
+		if err == nil && len(images) > 0 {
+			// TODO: log error
+			return config.Image, nil
+		}
+	}
+
 	ref, err := reference.ParseNormalizedNamed(config.Image)
 	if err != nil {
 		return "", err