cli/formatter: bracket IPv6 addrs prepended to ports

On `docker ps`, port bindings with an IPv6 HostIP should have their
addresses put into brackets when joining them to their ports.

RFC 3986 (Section 3.2.2) stipulates that IPv6 addresses should be
enclosed within square brackets. This RFC is only about URIs. However,
doing so here helps user identifier what's part of the IP address and
what's the port. It also makes it easier to copy/paste that
'[addr]:port' into other software (including browsers).

Signed-off-by: Albin Kerouanton <albinker@gmail.com>
(cherry picked from commit 964155cd27)
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

cli/command/formatter/container.go

@@ -5,6 +5,7 @@ package formatter
 
 import (
 	"fmt"
+	"net"
 	"sort"
 	"strconv"
 	"strings"
@@ -331,7 +332,8 @@ func DisplayablePorts(ports []types.Port) string {
 		portKey := port.Type
 		if port.IP != "" {
 			if port.PublicPort != current {
-				hostMappings = append(hostMappings, fmt.Sprintf("%s:%d->%d/%s", port.IP, port.PublicPort, port.PrivatePort, port.Type))
+				hAddrPort := net.JoinHostPort(port.IP, strconv.Itoa(int(port.PublicPort)))
+				hostMappings = append(hostMappings, fmt.Sprintf("%s->%d/%s", hAddrPort, port.PrivatePort, port.Type))
 				continue
 			}
 			portKey = port.IP + "/" + port.Type

cli/command/formatter/container_test.go

@@ -471,6 +471,16 @@ func TestDisplayablePorts(t *testing.T) {
 			},
 			"0.0.0.0:0->9988/tcp",
 		},
+		{
+			[]types.Port{
+				{
+					IP:          "::",
+					PrivatePort: 9988,
+					Type:        "tcp",
+				},
+			},
+			"[::]:0->9988/tcp",
+		},
 		{
 			[]types.Port{
 				{