Add an integration test for bug #31392 regression

This verifies that bug #31392 won't surface again.

To reproduce the bug:
1) docker run -dit --name a0 busybox sh
2) docker run -dit --name b0 --link a0 busybox sh
3) docker rename a0 a1
4) docker run -dit --name a0 busybox sh
5) docker rm -f b0
6) docker run -dit --name b0 --link a0 busybox sh

Signed-off-by: Boaz Shuster <ripcurld.github@gmail.com>

integration/container/rename_test.go

@@ -0,0 +1,88 @@
+package container
+
+import (
+	"context"
+	"testing"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/api/types/container"
+	"github.com/docker/docker/api/types/network"
+	"github.com/docker/docker/api/types/strslice"
+	"github.com/docker/docker/client"
+	"github.com/docker/docker/integration/util/request"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func runContainer(ctx context.Context, t *testing.T, client client.APIClient, cntCfg *container.Config, hstCfg *container.HostConfig, nwkCfg *network.NetworkingConfig, cntName string) string {
+	cnt, err := client.ContainerCreate(ctx, cntCfg, hstCfg, nwkCfg, cntName)
+	require.NoError(t, err)
+
+	err = client.ContainerStart(ctx, cnt.ID, types.ContainerStartOptions{})
+	require.NoError(t, err)
+	return cnt.ID
+}
+
+// This test simulates the scenario mentioned in #31392:
+// Having two linked container, renaming the target and bringing a replacement
+// and then deleting and recreating the source container linked to the new target.
+// This checks that "rename" updates source container correctly and doesn't set it to null.
+func TestRenameLinkedContainer(t *testing.T) {
+	defer setupTest(t)()
+	ctx := context.Background()
+	client := request.NewAPIClient(t)
+
+	cntConfig := &container.Config{
+		Image: "busybox",
+		Tty:   true,
+		Cmd:   strslice.StrSlice([]string{"top"}),
+	}
+
+	var (
+		aID, bID string
+		cntJSON  types.ContainerJSON
+		err      error
+	)
+
+	aID = runContainer(ctx, t, client,
+		cntConfig,
+		&container.HostConfig{},
+		&network.NetworkingConfig{},
+		"a0",
+	)
+
+	bID = runContainer(ctx, t, client,
+		cntConfig,
+		&container.HostConfig{
+			Links: []string{"a0"},
+		},
+		&network.NetworkingConfig{},
+		"b0",
+	)
+
+	err = client.ContainerRename(ctx, aID, "a1")
+	require.NoError(t, err)
+
+	runContainer(ctx, t, client,
+		cntConfig,
+		&container.HostConfig{},
+		&network.NetworkingConfig{},
+		"a0",
+	)
+
+	err = client.ContainerRemove(ctx, bID, types.ContainerRemoveOptions{Force: true})
+	require.NoError(t, err)
+
+	bID = runContainer(ctx, t, client,
+		cntConfig,
+		&container.HostConfig{
+			Links: []string{"a0"},
+		},
+		&network.NetworkingConfig{},
+		"b0",
+	)
+
+	cntJSON, err = client.ContainerInspect(ctx, bID)
+	require.NoError(t, err)
+	assert.Equal(t, []string{"/a0:/b0/a0"}, cntJSON.HostConfig.Links)
+}