Improve coding style

* Add a shared method in getPackages for AptAnalyzer and AptLayerAnalyzer
* Explicit validation of the type flag in includeLayers method

Author: davidcassany

cmd/root.go

@@ -59,6 +59,8 @@ const (
 	RemotePrefix = "remote://"
 )
 
+var layerAnalyzers = [...]string{"layer", "aptlayer"}
+
 var RootCmd = &cobra.Command{
 	Use:   "container-diff",
 	Short: "container-diff is a tool for analyzing and comparing container images",
@@ -268,8 +270,10 @@ func getExtractPathForName(name string) (string, error) {
 
 func includeLayers() bool {
 	for _, t := range types {
-		if strings.Contains(t, "layer") {
-			return true
+		for _, a := range layerAnalyzers {
+			if t == a {
+				return true
+			}
 		}
 	}
 	return false

differs/apt_diff.go

@@ -50,13 +50,16 @@ func (a AptAnalyzer) Analyze(image pkgutil.Image) (util.Result, error) {
 }
 
 func (a AptAnalyzer) getPackages(image pkgutil.Image) (map[string]util.PackageInfo, error) {
-	path := image.FSPath
+	return readStatusFile(image.FSPath)
+}
+
+func readStatusFile(root string) (map[string]util.PackageInfo, error) {
 	packages := make(map[string]util.PackageInfo)
-	if _, err := os.Stat(path); err != nil {
+	if _, err := os.Stat(root); err != nil {
 		// invalid image directory path
 		return packages, err
 	}
-	statusFile := filepath.Join(path, dpkgStatusFile)
+	statusFile := filepath.Join(root, dpkgStatusFile)
 	if _, err := os.Stat(statusFile); err != nil {
 		// status file does not exist in this layer
 		return packages, nil
@@ -154,28 +157,10 @@ func (a AptLayerAnalyzer) getPackages(image pkgutil.Image) ([]map[string]util.Pa
 		return packages, nil
 	}
 	for _, layer := range image.Layers {
-		layerPackages := make(map[string]util.PackageInfo)
-		if _, err := os.Stat(layer.FSPath); err != nil {
-			// invalid layer directory path
+		layerPackages, err := readStatusFile(layer.FSPath)
+		if err != nil {
 			return packages, err
 		}
-		statusFile := filepath.Join(layer.FSPath, dpkgStatusFile)
-		if _, err := os.Stat(statusFile); err == nil {
-			// this layer has a package database
-			if file, err := os.Open(statusFile); err == nil {
-				// make sure it gets closed
-				defer file.Close()
-
-				// create a new scanner and read the file line by line
-				scanner := bufio.NewScanner(file)
-				var currPackage string
-				for scanner.Scan() {
-					currPackage = parseLine(scanner.Text(), currPackage, layerPackages)
-				}
-			} else {
-				return packages, err
-			}
-		}
 		packages = append(packages, layerPackages)
 	}