Add label filter for docker system prune

This fix tries to address the issue raised in 29999 where it was not
possible to mask these items (like important non-removable stuff)
from `docker system prune`.

This fix adds `label` and `label!` field for `--filter` in `system prune`,
so that it is possible to selectively prune items like:
```
$ docker container prune --filter label=foo

$ docker container prune --filter label!=bar
```

Additional unit tests and integration tests have been added.

This fix fixes 29999.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
Upstream-commit: c3bfcc372c
Component: cli

components/cli/container_prune_test.go

@@ -40,6 +40,11 @@ func TestContainersPrune(t *testing.T) {
 	danglingUntilFilters.Add("dangling", "true")
 	danglingUntilFilters.Add("until", "2016-12-15T14:00")
 
+	labelFilters := filters.NewArgs()
+	labelFilters.Add("dangling", "true")
+	labelFilters.Add("label", "label1=foo")
+	labelFilters.Add("label", "label2!=bar")
+
 	listCases := []struct {
 		filters             filters.Args
 		expectedQueryParams map[string]string
@@ -76,6 +81,14 @@ func TestContainersPrune(t *testing.T) {
 				"filters": `{"dangling":{"false":true}}`,
 			},
 		},
+		{
+			filters: labelFilters,
+			expectedQueryParams: map[string]string{
+				"until":   "",
+				"filter":  "",
+				"filters": `{"dangling":{"true":true},"label":{"label1=foo":true,"label2!=bar":true}}`,
+			},
+		},
 	}
 	for _, listCase := range listCases {
 		client := &Client{

components/cli/image_prune_test.go

@@ -36,6 +36,11 @@ func TestImagesPrune(t *testing.T) {
 	noDanglingFilters := filters.NewArgs()
 	noDanglingFilters.Add("dangling", "false")
 
+	labelFilters := filters.NewArgs()
+	labelFilters.Add("dangling", "true")
+	labelFilters.Add("label", "label1=foo")
+	labelFilters.Add("label", "label2!=bar")
+
 	listCases := []struct {
 		filters             filters.Args
 		expectedQueryParams map[string]string
@@ -64,6 +69,14 @@ func TestImagesPrune(t *testing.T) {
 				"filters": `{"dangling":{"false":true}}`,
 			},
 		},
+		{
+			filters: labelFilters,
+			expectedQueryParams: map[string]string{
+				"until":   "",
+				"filter":  "",
+				"filters": `{"dangling":{"true":true},"label":{"label1=foo":true,"label2!=bar":true}}`,
+			},
+		},
 	}
 	for _, listCase := range listCases {
 		client := &Client{

components/cli/network_prune_test.go

@@ -38,6 +38,11 @@ func TestNetworksPrune(t *testing.T) {
 	noDanglingFilters := filters.NewArgs()
 	noDanglingFilters.Add("dangling", "false")
 
+	labelFilters := filters.NewArgs()
+	labelFilters.Add("dangling", "true")
+	labelFilters.Add("label", "label1=foo")
+	labelFilters.Add("label", "label2!=bar")
+
 	listCases := []struct {
 		filters             filters.Args
 		expectedQueryParams map[string]string
@@ -66,6 +71,14 @@ func TestNetworksPrune(t *testing.T) {
 				"filters": `{"dangling":{"false":true}}`,
 			},
 		},
+		{
+			filters: labelFilters,
+			expectedQueryParams: map[string]string{
+				"until":   "",
+				"filter":  "",
+				"filters": `{"dangling":{"true":true},"label":{"label1=foo":true,"label2!=bar":true}}`,
+			},
+		},
 	}
 	for _, listCase := range listCases {
 		client := &Client{