image ls: show each tag for an image as a separate entry

A single image can be tagged under multiple names. While they are the
same image under the hood (same digest), we always presented these as
separate images in the list.

This patch applies the same behavior for the tree view; we can consider
having some "compact" presentation in future where we collapse these iamges
(perhaps introducing a "names" column?)

Before this patch:

    $ docker pull --quiet alpine:3.20
    docker.io/library/alpine:3.20
    $ docker pull --quiet alpine:latest
    docker.io/library/alpine:latest

    $ docker image ls --tree

    IMAGE                   ID             DISK USAGE   CONTENT SIZE   USED
    alpine:3.20
    alpine:latest           beefdbd8a1da       13.6MB         4.09MB
    ├─ linux/arm64/v8       9cee2b382fe2       13.6MB         4.09MB
    ├─ linux/amd64          33735bd63cf8           0B             0B
    ├─ linux/arm/v6         50f635c8b04d           0B             0B
    ├─ linux/arm/v7         f2f82d424957           0B             0B
    ├─ linux/386            b3e87f642f5c           0B             0B
    ├─ linux/ppc64le        c7a6800e3dc5           0B             0B
    ├─ linux/riscv64        80cde017a105           0B             0B
    └─ linux/s390x          2b5b26e09ca2           0B             0B

With this patch applied:

    $ docker image ls --tree

    IMAGE                   ID             DISK USAGE   CONTENT SIZE   USED
    alpine:3.20             beefdbd8a1da       13.6MB         4.09MB
    ├─ linux/arm64/v8       9cee2b382fe2       13.6MB         4.09MB
    ├─ linux/amd64          33735bd63cf8           0B             0B
    ├─ linux/arm/v6         50f635c8b04d           0B             0B
    ├─ linux/arm/v7         f2f82d424957           0B             0B
    ├─ linux/386            b3e87f642f5c           0B             0B
    ├─ linux/ppc64le        c7a6800e3dc5           0B             0B
    ├─ linux/riscv64        80cde017a105           0B             0B
    └─ linux/s390x          2b5b26e09ca2           0B             0B

    alpine:latest           beefdbd8a1da       13.6MB         4.09MB
    ├─ linux/arm64/v8       9cee2b382fe2       13.6MB         4.09MB
    ├─ linux/amd64          33735bd63cf8           0B             0B
    ├─ linux/arm/v6         50f635c8b04d           0B             0B
    ├─ linux/arm/v7         f2f82d424957           0B             0B
    ├─ linux/386            b3e87f642f5c           0B             0B
    ├─ linux/ppc64le        c7a6800e3dc5           0B             0B
    ├─ linux/riscv64        80cde017a105           0B             0B
    └─ linux/s390x          2b5b26e09ca2           0B             0B

Signed-off-by: Sebastiaan van Stijn <[email protected]>

cli/command/image/tree.go

@@ -82,12 +82,25 @@ 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.Slice(view.images, func(i, j int) bool {