image ls --tree: order images alphabetically

cli/command/image/tree.go

@@ -14,6 +14,7 @@ import (
 	imagetypes "github.com/docker/docker/api/types/image"
 	"github.com/docker/docker/pkg/stringid"
 	"github.com/docker/go-units"
+	"github.com/fvbommel/sortorder"
 	"github.com/morikuni/aec"
 )
 
@@ -82,16 +83,46 @@ func runTree(ctx context.Context, dockerCLI command.Cli, opts treeOptions) error
 
 		details.ContentSize = units.HumanSizeWithPrecision(float64(totalContent), 3)
 
-		view.images = append(view.images, topImage{
-			Names:    img.RepoTags,
-			Details:  details,
-			Children: children,
-			created:  img.Created,
-		})
+		if len(img.RepoTags) == 0 {
+			// Untagged image
+			view.images = append(view.images, topImage{
+				Names:    img.RepoTags,
+				Details:  details,
+				Children: children,
+				created:  img.Created,
+			})
+		} else {
+			// Present images tagged under multiple names as separate images.
+			for _, n := range img.RepoTags {
+				view.images = append(view.images, topImage{
+					Names:    []string{n}, // Consider changing Names to be a single name for purpose of this presentation.
+					Details:  details,
+					Children: children,
+					created:  img.Created,
+				})
+			}
+		}
 	}
 
+	// Sort images alphabetically using natural-sort, with untagged images last.
 	sort.Slice(view.images, func(i, j int) bool {
-		return view.images[i].created > view.images[j].created
+		iUntagged, jUntagged := len(view.images[i].Names) == 0, len(view.images[j].Names) == 0
+		if iUntagged || jUntagged {
+			switch {
+			case iUntagged && jUntagged:
+				// Both untagged images; sort by created date (desc)
+				return view.images[i].created > view.images[j].created
+			case iUntagged:
+				// Sort untagged images last
+				return false
+			case jUntagged:
+				// Sort untagged images last
+				return true
+			}
+		}
+
+		// Sort alphabetically, ascending
+		return sortorder.NaturalLess(view.images[i].Names[0], view.images[j].Names[0])
 	})
 
 	return printImageTree(dockerCLI, view)