figuring out evocation pathway, cacheDir should be consistent between modules

Author: vsoch

cmd/root.go

@@ -39,6 +39,7 @@ var save bool
 var types diffTypes
 var noCache bool
 
+var cacheDir string
 var LogLevel string
 var format string
 
@@ -129,15 +130,18 @@ func getImage(imageName string) (pkgutil.Image, error) {
 	var cachePath string
 	var err error
 	if !noCache {
-		cachePath, err = cacheDir(imageName)
+		cachePath, err = getCacheDir(imageName, cacheDir)
 		if err != nil {
 			return pkgutil.Image{}, err
 		}
 	}
 	return pkgutil.GetImage(imageName, includeLayers(), cachePath)
 }
 
-func cacheDir(imageName string) (string, error) {
+func getCacheDir(imageName string, cacheDir string) (string, error) {
+	// If the user has specified a custom cache directory
+        // TODO: write me
+        // else
 	dir, err := homedir.Dir()
 	if err != nil {
 		return "", err
@@ -185,4 +189,5 @@ func addSharedFlags(cmd *cobra.Command) {
 	cmd.Flags().BoolVarP(&save, "save", "s", false, "Set this flag to save rather than remove the final image filesystems on exit.")
 	cmd.Flags().BoolVarP(&util.SortSize, "order", "o", false, "Set this flag to sort any file/package results by descending size. Otherwise, they will be sorted by name.")
 	cmd.Flags().BoolVarP(&noCache, "no-cache", "n", false, "Set this to force retrieval of image filesystem on each run.")
+        cmd.Flags().StringVar(&cacheDir, "cache", "", "cache directory base to create .container-diff (default is $HOME).")
 }