do not diff image sha or hostname in metadata

differs/metadata_diff.go

@@ -80,7 +80,6 @@ func getMetadataList(image pkgutil.Image) ([]string, error) {
 	}
 	c := configFile.Config
 	return []string{
-		fmt.Sprintf("Hostname: %s", c.Hostname),
 		fmt.Sprintf("Domainname: %s", c.Domainname),
 		fmt.Sprintf("User: %s", c.User),
 		fmt.Sprintf("AttachStdin: %t", c.AttachStdin),
@@ -93,7 +92,6 @@ func getMetadataList(image pkgutil.Image) ([]string, error) {
 		fmt.Sprintf("Env: %s", strings.Join(c.Env, ",")),
 		fmt.Sprintf("Cmd: %s", strings.Join(c.Cmd, ",")),
 		fmt.Sprintf("ArgsEscaped: %t", c.ArgsEscaped),
-		fmt.Sprintf("Image: %s", c.Image),
 		fmt.Sprintf("Volumes: %v", pkgutil.SortMap(c.Volumes)),
 		fmt.Sprintf("Workdir: %s", c.WorkingDir),
 		fmt.Sprintf("Entrypoint: %s", strings.Join(c.Entrypoint, ",")),

tests/metadata_diff_expected.json

@@ -6,14 +6,12 @@
     "Diff": {
       "Adds": [
         "ExposedPorts: 1234/tcp:{}",
-        "Image: sha256:0b30c570b95ba9cc450c8252cb264a8c66f7492a7dd6fb32f356267b9e04038f",
         "Entrypoint: /entrypoint"
       ],
       "Dels": [
         "ExposedPorts: 1234/tcp:{} 4321/tcp:{}",
-        "Image: sha256:63d847f046cdda00df8ba9176753059439478784129443dd1da632504dce95bb",
         "Entrypoint: "
       ]
     }
   }
-]
+]