add --from option to context create

--from creates a context from a named context.
By default `context create` will create a context from the current context.
Replaced "from-current=" docker/kubernetes option with "from=" to allow specifying which context to copy the settings from.

Signed-off-by: Nick Adcock <nick.adcock@docker.com>

cli/command/context/create.go

@@ -21,6 +21,7 @@ type CreateOptions struct {
 	DefaultStackOrchestrator string
 	Docker                   map[string]string
 	Kubernetes               map[string]string
+	From                     string
 }
 
 func longCreateDescription() string {
@@ -63,6 +64,7 @@ func newCreateCommand(dockerCli command.Cli) *cobra.Command {
 		"Default orchestrator for stack operations to use with this context (swarm|kubernetes|all)")
 	flags.StringToStringVar(&opts.Docker, "docker", nil, "set the docker endpoint")
 	flags.StringToStringVar(&opts.Kubernetes, "kubernetes", nil, "set the kubernetes endpoint")
+	flags.StringVar(&opts.From, "from", "", "create context from a named context")
 	return cmd
 }
 
@@ -76,17 +78,20 @@ func RunCreate(cli command.Cli, o *CreateOptions) error {
 	if err != nil {
 		return errors.Wrap(err, "unable to parse default-stack-orchestrator")
 	}
-	contextMetadata := store.ContextMetadata{
+	if o.From == "" && o.Docker == nil && o.Kubernetes == nil {
-		Endpoints: make(map[string]interface{}),
+		return createFromExistingContext(s, cli.CurrentContext(), stackOrchestrator, o)
-		Metadata: command.DockerContext{
-			Description:       o.Description,
-			StackOrchestrator: stackOrchestrator,
-		},
-		Name: o.Name,
 	}
+	if o.From != "" {
+		return createFromExistingContext(s, o.From, stackOrchestrator, o)
+	}
+	return createNewContext(o, stackOrchestrator, cli, s)
+}
+
+func createNewContext(o *CreateOptions, stackOrchestrator command.Orchestrator, cli command.Cli, s store.Store) error {
 	if o.Docker == nil {
 		return errors.New("docker endpoint configuration is required")
 	}
+	contextMetadata := newContextMetadata(stackOrchestrator, o)
 	contextTLSData := store.ContextTLSData{
 		Endpoints: make(map[string]store.EndpointTLSData),
 	}
@@ -139,3 +144,52 @@ func checkContextNameForCreation(s store.Store, name string) error {
 	}
 	return nil
 }
+
+func createFromExistingContext(s store.Store, fromContextName string, stackOrchestrator command.Orchestrator, o *CreateOptions) error {
+	if len(o.Docker) != 0 || len(o.Kubernetes) != 0 {
+		return errors.New("cannot use --docker or --kubernetes flags when --from is set")
+	}
+	reader := store.Export(fromContextName, &descriptionAndOrchestratorStoreDecorator{
+		Store:        s,
+		description:  o.Description,
+		orchestrator: stackOrchestrator,
+	})
+	defer reader.Close()
+	return store.Import(o.Name, s, reader)
+}
+
+type descriptionAndOrchestratorStoreDecorator struct {
+	store.Store
+	description  string
+	orchestrator command.Orchestrator
+}
+
+func (d *descriptionAndOrchestratorStoreDecorator) GetContextMetadata(name string) (store.ContextMetadata, error) {
+	c, err := d.Store.GetContextMetadata(name)
+	if err != nil {
+		return c, err
+	}
+	typedContext, err := command.GetDockerContext(c)
+	if err != nil {
+		return c, err
+	}
+	if d.description != "" {
+		typedContext.Description = d.description
+	}
+	if d.orchestrator != command.Orchestrator("") {
+		typedContext.StackOrchestrator = d.orchestrator
+	}
+	c.Metadata = typedContext
+	return c, nil
+}
+
+func newContextMetadata(stackOrchestrator command.Orchestrator, o *CreateOptions) store.ContextMetadata {
+	return store.ContextMetadata{
+		Endpoints: make(map[string]interface{}),
+		Metadata: command.DockerContext{
+			Description:       o.Description,
+			StackOrchestrator: stackOrchestrator,
+		},
+		Name: o.Name,
+	}
+}

cli/command/context/create_test.go

@@ -105,13 +105,6 @@ func TestCreateInvalids(t *testing.T) {
 			},
 			expecterErr: `specified orchestrator "invalid" is invalid, please use either kubernetes, swarm or all`,
 		},
-		{
-			options: CreateOptions{
-				Name:                     "orchestrator-swarm-no-endpoint",
-				DefaultStackOrchestrator: "swarm",
-			},
-			expecterErr: `docker endpoint configuration is required`,
-		},
 		{
 			options: CreateOptions{
 				Name:                     "orchestrator-kubernetes-no-endpoint",
@@ -185,7 +178,7 @@ func createTestContextWithKube(t *testing.T, cli command.Cli) {
 		Name:                     "test",
 		DefaultStackOrchestrator: "all",
 		Kubernetes: map[string]string{
-			keyFromCurrent: "true",
+			keyFrom: "default",
 		},
 		Docker: map[string]string{},
 	})
@@ -198,3 +191,157 @@ func TestCreateOrchestratorAllKubernetesEndpointFromCurrent(t *testing.T) {
 	createTestContextWithKube(t, cli)
 	validateTestKubeEndpoint(t, cli.ContextStore(), "test")
 }
+
+func TestCreateFromContext(t *testing.T) {
+	cases := []struct {
+		name                 string
+		description          string
+		orchestrator         string
+		expectedDescription  string
+		docker               map[string]string
+		kubernetes           map[string]string
+		expectedOrchestrator command.Orchestrator
+	}{
+		{
+			name:                 "no-override",
+			expectedDescription:  "original description",
+			expectedOrchestrator: command.OrchestratorSwarm,
+		},
+		{
+			name:                 "override-description",
+			description:          "new description",
+			expectedDescription:  "new description",
+			expectedOrchestrator: command.OrchestratorSwarm,
+		},
+		{
+			name:                 "override-orchestrator",
+			orchestrator:         "kubernetes",
+			expectedDescription:  "original description",
+			expectedOrchestrator: command.OrchestratorKubernetes,
+		},
+	}
+
+	cli, cleanup := makeFakeCli(t)
+	defer cleanup()
+	revert := env.Patch(t, "KUBECONFIG", "./testdata/test-kubeconfig")
+	defer revert()
+	assert.NilError(t, RunCreate(cli, &CreateOptions{
+		Name:        "original",
+		Description: "original description",
+		Docker: map[string]string{
+			keyHost: "tcp://42.42.42.42:2375",
+		},
+		Kubernetes: map[string]string{
+			keyFrom: "default",
+		},
+		DefaultStackOrchestrator: "swarm",
+	}))
+	assert.NilError(t, RunCreate(cli, &CreateOptions{
+		Name:        "dummy",
+		Description: "dummy description",
+		Docker: map[string]string{
+			keyHost: "tcp://24.24.24.24:2375",
+		},
+		Kubernetes: map[string]string{
+			keyFrom: "default",
+		},
+		DefaultStackOrchestrator: "swarm",
+	}))
+
+	cli.SetCurrentContext("dummy")
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			err := RunCreate(cli, &CreateOptions{
+				From:                     "original",
+				Name:                     c.name,
+				Description:              c.description,
+				DefaultStackOrchestrator: c.orchestrator,
+				Docker:                   c.docker,
+				Kubernetes:               c.kubernetes,
+			})
+			assert.NilError(t, err)
+			newContext, err := cli.ContextStore().GetContextMetadata(c.name)
+			assert.NilError(t, err)
+			newContextTyped, err := command.GetDockerContext(newContext)
+			assert.NilError(t, err)
+			dockerEndpoint, err := docker.EndpointFromContext(newContext)
+			assert.NilError(t, err)
+			kubeEndpoint := kubernetes.EndpointFromContext(newContext)
+			assert.Check(t, kubeEndpoint != nil)
+			assert.Equal(t, newContextTyped.Description, c.expectedDescription)
+			assert.Equal(t, newContextTyped.StackOrchestrator, c.expectedOrchestrator)
+			assert.Equal(t, dockerEndpoint.Host, "tcp://42.42.42.42:2375")
+			assert.Equal(t, kubeEndpoint.Host, "https://someserver")
+		})
+	}
+}
+
+func TestCreateFromCurrent(t *testing.T) {
+	cases := []struct {
+		name                 string
+		description          string
+		orchestrator         string
+		expectedDescription  string
+		expectedOrchestrator command.Orchestrator
+	}{
+		{
+			name:                 "no-override",
+			expectedDescription:  "original description",
+			expectedOrchestrator: command.OrchestratorSwarm,
+		},
+		{
+			name:                 "override-description",
+			description:          "new description",
+			expectedDescription:  "new description",
+			expectedOrchestrator: command.OrchestratorSwarm,
+		},
+		{
+			name:                 "override-orchestrator",
+			orchestrator:         "kubernetes",
+			expectedDescription:  "original description",
+			expectedOrchestrator: command.OrchestratorKubernetes,
+		},
+	}
+
+	cli, cleanup := makeFakeCli(t)
+	defer cleanup()
+	revert := env.Patch(t, "KUBECONFIG", "./testdata/test-kubeconfig")
+	defer revert()
+	assert.NilError(t, RunCreate(cli, &CreateOptions{
+		Name:        "original",
+		Description: "original description",
+		Docker: map[string]string{
+			keyHost: "tcp://42.42.42.42:2375",
+		},
+		Kubernetes: map[string]string{
+			keyFrom: "default",
+		},
+		DefaultStackOrchestrator: "swarm",
+	}))
+
+	cli.SetCurrentContext("original")
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			err := RunCreate(cli, &CreateOptions{
+				Name:                     c.name,
+				Description:              c.description,
+				DefaultStackOrchestrator: c.orchestrator,
+			})
+			assert.NilError(t, err)
+			newContext, err := cli.ContextStore().GetContextMetadata(c.name)
+			assert.NilError(t, err)
+			newContextTyped, err := command.GetDockerContext(newContext)
+			assert.NilError(t, err)
+			dockerEndpoint, err := docker.EndpointFromContext(newContext)
+			assert.NilError(t, err)
+			kubeEndpoint := kubernetes.EndpointFromContext(newContext)
+			assert.Check(t, kubeEndpoint != nil)
+			assert.Equal(t, newContextTyped.Description, c.expectedDescription)
+			assert.Equal(t, newContextTyped.StackOrchestrator, c.expectedOrchestrator)
+			assert.Equal(t, dockerEndpoint.Host, "tcp://42.42.42.42:2375")
+			assert.Equal(t, kubeEndpoint.Host, "https://someserver")
+		})
+	}
+}

cli/command/context/list_test.go

@@ -17,7 +17,7 @@ func createTestContextWithKubeAndSwarm(t *testing.T, cli command.Cli, name strin
 		Name:                     name,
 		DefaultStackOrchestrator: orchestrator,
 		Description:              "description of " + name,
-		Kubernetes:               map[string]string{keyFromCurrent: "true"},
+		Kubernetes:               map[string]string{keyFrom: "default"},
 		Docker:                   map[string]string{keyHost: "https://someswarmserver"},
 	})
 	assert.NilError(t, err)

cli/command/context/options.go

@@ -18,7 +18,7 @@ import (
 )
 
 const (
-	keyFromCurrent   = "from-current"
+	keyFrom          = "from"
 	keyHost          = "host"
 	keyCA            = "ca"
 	keyCert          = "cert"
@@ -36,7 +36,7 @@ type configKeyDescription struct {
 
 var (
 	allowedDockerConfigKeys = map[string]struct{}{
-		keyFromCurrent:   {},
+		keyFrom:          {},
 		keyHost:          {},
 		keyCA:            {},
 		keyCert:          {},
@@ -44,15 +44,15 @@ var (
 		keySkipTLSVerify: {},
 	}
 	allowedKubernetesConfigKeys = map[string]struct{}{
-		keyFromCurrent:   {},
+		keyFrom:          {},
 		keyKubeconfig:    {},
 		keyKubecontext:   {},
 		keyKubenamespace: {},
 	}
 	dockerConfigKeysDescriptions = []configKeyDescription{
 		{
-			name:        keyFromCurrent,
+			name:        keyFrom,
-			description: "Copy current Docker endpoint configuration",
+			description: "Copy named context's Docker endpoint configuration",
 		},
 		{
 			name:        keyHost,
@@ -77,8 +77,8 @@ var (
 	}
 	kubernetesConfigKeysDescriptions = []configKeyDescription{
 		{
-			name:        keyFromCurrent,
+			name:        keyFrom,
-			description: "Copy current Kubernetes endpoint configuration",
+			description: "Copy named context's Kubernetes endpoint configuration",
 		},
 		{
 			name:        keyKubeconfig,
@@ -121,12 +121,15 @@ func getDockerEndpoint(dockerCli command.Cli, config map[string]string) (docker.
 	if err := validateConfig(config, allowedDockerConfigKeys); err != nil {
 		return docker.Endpoint{}, err
 	}
-	fromCurrent, err := parseBool(config, keyFromCurrent)
+	if contextName, ok := config[keyFrom]; ok {
+		metadata, err := dockerCli.ContextStore().GetContextMetadata(contextName)
 		if err != nil {
 			return docker.Endpoint{}, err
 		}
-	if fromCurrent {
+		if ep, ok := metadata.Endpoints[docker.DockerEndpoint].(docker.EndpointMeta); ok {
-		return dockerCli.DockerEndpoint(), nil
+			return docker.Endpoint{EndpointMeta: ep}, nil
+		}
+		return docker.Endpoint{}, errors.Errorf("unable to get endpoint from context %q", contextName)
 	}
 	tlsData, err := context.TLSDataFromFiles(config[keyCA], config[keyCert], config[keyKey])
 	if err != nil {
@@ -169,13 +172,8 @@ func getKubernetesEndpoint(dockerCli command.Cli, config map[string]string) (*ku
 	if len(config) == 0 {
 		return nil, nil
 	}
-	fromCurrent, err := parseBool(config, keyFromCurrent)
+	if contextName, ok := config[keyFrom]; ok {
-	if err != nil {
+		ctxMeta, err := dockerCli.ContextStore().GetContextMetadata(contextName)
-		return nil, err
-	}
-	if fromCurrent {
-		if dockerCli.CurrentContext() != "" {
-			ctxMeta, err := dockerCli.ContextStore().GetContextMetadata(dockerCli.CurrentContext())
 		if err != nil {
 			return nil, err
 		}
@@ -187,7 +185,7 @@ func getKubernetesEndpoint(dockerCli command.Cli, config map[string]string) (*ku
 			}
 			return &res, nil
 		}
-		}
+
 		// fallback to env-based kubeconfig
 		kubeconfig := os.Getenv("KUBECONFIG")
 		if kubeconfig == "" {

docs/reference/commandline/context_create.md

@@ -23,7 +23,7 @@ Create a context
 Docker endpoint config:
 
 NAME                DESCRIPTION
-from-current        Copy current Docker endpoint configuration
+from                Copy Docker endpoint configuration from an existing context
 host                Docker endpoint on which to connect
 ca                  Trust certs signed only by this CA
 cert                Path to TLS certificate file
@@ -33,14 +33,16 @@ skip-tls-verify     Skip TLS certificate validation
 Kubernetes endpoint config:
 
 NAME                 DESCRIPTION
-from-current         Copy current Kubernetes endpoint configuration
+from                 Copy Kubernetes endpoint configuration from an existing context
 config-file          Path to a Kubernetes config file
 context-override     Overrides the context set in the kubernetes config file
 namespace-override   Overrides the namespace set in the kubernetes config file
 
 Example:
 
-$ docker context create my-context --description "some description" --docker "host=tcp://myserver:2376,ca=~/ca-file,cert=~/cert-file,key=~/key-file"
+$ docker context create my-context \
+      --description "some description" \
+      --docker "host=tcp://myserver:2376,ca=~/ca-file,cert=~/cert-file,key=~/key-file"
 
 Options:
       --default-stack-orchestrator string   Default orchestrator for
@@ -52,24 +54,68 @@ Options:
                                             (default [])
       --kubernetes stringToString           set the kubernetes endpoint
                                             (default [])
+      --from string                         Create the context from an existing context
 ```
 
 ## Description
 
-Creates a new `context`. This will allow you to quickly switch the cli configuration to connect to different clusters or single nodes.
+Creates a new `context`. This allows you to quickly switch the cli
+configuration to connect to different clusters or single nodes.
 
-To create a `context` out of an existing `DOCKER_HOST` based script, you can use the `from-current` config key:
+To create a context from scratch provide the docker and, if required,
+kubernetes options. The example below creates the context `my-context`
+with a docker endpoint of `/var/run/docker.sock` and a kubernetes configuration
+sourced from the file `/home/me/my-kube-config`:
+
+```bash
+$ docker context create my-context \
+      --docker host=/var/run/docker.sock \
+      --kubernetes config-file=/home/me/my-kube-config
+```
+
+Use the `--from=<context-name>` option to create a new context from
+an existing context. The example below creates a new context named `my-context`
+from the existing context `existing-context`:
+
+```bash
+$ docker context create my-context --from existing-context
+```
+
+If the `--from` option is not set, the `context` is created from the current context:
+
+```bash
+$ docker context create my-context
+```
+
+This can be used to create a context out of an existing `DOCKER_HOST` based script:
 
 ```bash
 $ source my-setup-script.sh
-$ docker context create my-context --docker "from-current=true"
+$ docker context create my-context
 ```
 
-Similarly, to reference the currently active Kubernetes configuration, you can use `--kubernetes "from-current=true"`:
+To source only the `docker` endpoint configuration from an existing context
+use the `--docker from=<context-name>` option. The example below creates a
+new context named `my-context` using the docker endpoint configuration from
+the existing context `existing-context` and a kubernetes configuration sourced
+from the file `/home/me/my-kube-config`:
 
 ```bash
-$ export KUBECONFIG=/path/to/my/kubeconfig
+$ docker context create my-context \
-$ docker context create my-context --kubernetes "from-current=true" --docker "host=/var/run/docker.sock"
+      --docker from=existing-context \
+      --kubernetes config-file=/home/me/my-kube-config
 ```
 
-Docker and Kubernetes endpoints configurations, as well as default stack orchestrator and description can be modified with `docker context update`
+To source only the `kubernetes` configuration from an existing context use the
+`--kubernetes from=<context-name>` option. The example below creates a new
+context named `my-context` using the kuberentes configuration from the existing
+context `existing-context` and a docker endpoint of `/var/run/docker.sock`:
+
+```bash
+$ docker context create my-context \
+      --docker host=/var/run/docker.sock \
+      --kubernetes from=existing-context
+```
+
+Docker and Kubernetes endpoints configurations, as well as default stack
+orchestrator and description can be modified with `docker context update`

docs/reference/commandline/context_update.md

@@ -23,7 +23,7 @@ Update a context
 Docker endpoint config:
 
 NAME                DESCRIPTION
-from-current        Copy current Docker endpoint configuration
+from                Copy Docker endpoint configuration from an existing context
 host                Docker endpoint on which to connect
 ca                  Trust certs signed only by this CA
 cert                Path to TLS certificate file
@@ -33,7 +33,7 @@ skip-tls-verify     Skip TLS certificate validation
 Kubernetes endpoint config:
 
 NAME                 DESCRIPTION
-from-current         Copy current Kubernetes endpoint configuration
+from                 Copy Kubernetes endpoint configuration from an existing context
 config-file          Path to a Kubernetes config file
 context-override     Overrides the context set in the kubernetes config file
 namespace-override   Overrides the namespace set in the kubernetes config file