refactor: isolate + inject DefinitionFetcher

cli/build.go

@@ -18,7 +18,7 @@ func getBuildCommand() *cobra.Command {
 			if err != nil {
 				return fmt.Errorf("%+v", err)
 			}
-			def, err := service_definition.GetServiceDefinition(pathProvided)
+			def, err := service_definition.NewDefinitionFetcher().GetDefinition(pathProvided)
 
 			if err != nil {
 				return fmt.Errorf("Failed to read service definition from file: %+v", err)

cli/start_service.go

@@ -49,7 +49,7 @@ func getStartCommand() *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			ctx := cmd.Context()
 			flags := ctx.Value("flags").(ParsedFlags)
-			def, err := service_definition.GetServiceDefinition(flags.definitionPath)
+			def, err := service_definition.NewDefinitionFetcher().GetDefinition(flags.definitionPath)
 
 			if err != nil {
 				return fmt.Errorf("Failed to read service definition: %+v", err)

service_definition/fetcher.go

@@ -7,26 +7,60 @@ import (
 	"strings"
 )
 
+// TODO: Extract into own module.
+type GitClient interface {
+	Clone(path string, destination string) (string, error)
+}
+
+type Git struct{}
+
+func (g Git) Clone(path string, destination string) (string, error) {
+	cloneCmd := exec.Command("git", "clone", path, destination)
+
+	if err := cloneCmd.Run(); err != nil {
+		return "", err
+	}
+
+	return path, nil
+}
+
+type DefinitionFetcher struct {
+	Git GitClient
+}
+
+func NewDefinitionFetcher() DefinitionFetcher {
+	return DefinitionFetcher{
+		Git: Git{},
+	}
+}
+
+// TODO: Add coverage.
+func (f DefinitionFetcher) GetDefinition(path string) (ServiceDefinition, error) {
+	if strings.HasPrefix(path, "git+") {
+		return f.getDefinitionFromGit(path)
+	}
+
+	return f.getDefinitionFromFile(path)
+}
+
 // Clones the target git repository and uses it as a basis to extract
 // a service definition.
-func getDefinitionFromGit(path string) (ServiceDefinition, error) {
+func (f DefinitionFetcher) getDefinitionFromGit(path string) (ServiceDefinition, error) {
 	dir, err := os.MkdirTemp("/tmp", "spud-service-")
 
 	if err != nil {
 		return ServiceDefinition{}, err
 	}
 
-	cloneCmd := exec.Command("git", "clone", strings.TrimPrefix(path, "git+"), dir)
+	if _, err := f.Git.Clone(strings.TrimPrefix(path, "git+"), dir); err != nil {
-
-	if err := cloneCmd.Run(); err != nil {
 		return ServiceDefinition{}, err
 	}
 
-	return getDefinitionFromFile(dir + "/service.yml")
+	return f.getDefinitionFromFile(dir + "/service.yml")
 }
 
 // Extracts a service definition from the given filepath.
-func getDefinitionFromFile(path string) (ServiceDefinition, error) {
+func (f DefinitionFetcher) getDefinitionFromFile(path string) (ServiceDefinition, error) {
 	var definition ServiceDefinition
 
 	defData, err := os.ReadFile(path)

service_definition/main.go

@@ -1,9 +1,5 @@
 package service_definition
 
-import (
-	"strings"
-)
-
 type BuildImage struct {
 	Path      string `yaml:"path"`
 	TagPrefix string `yaml:"tag"`
@@ -47,11 +43,3 @@ type ServiceDefinition struct {
 	Containers []ContainerDefinition `yaml:"containers"`
 	Ports      []PortMapping         `yaml:"ports"`
 }
-
-func GetServiceDefinition(path string) (ServiceDefinition, error) {
-	if strings.HasPrefix(path, "git+") {
-		return getDefinitionFromGit(path)
-	}
-
-	return getDefinitionFromFile(path)
-}

service_definition/service_definition_test.go

@@ -5,7 +5,7 @@ import (
 )
 
 func TestGetServiceDefinitionFromFileDoesNotExist(t *testing.T) {
-	_, err := GetServiceDefinition(t.TempDir() + "/not-a-file.yml")
+	_, err := NewDefinitionFetcher().GetDefinition(t.TempDir() + "/not-a-file.yml")
 
 	if err == nil {
 		t.Errorf("Expected error, got nil.")