introduce `context show` command

Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>

cli/command/context/cmd.go

@@ -23,6 +23,7 @@ func NewContextCommand(dockerCli command.Cli) *cobra.Command {
 		newRemoveCommand(dockerCli),
 		newUpdateCommand(dockerCli),
 		newInspectCommand(dockerCli),
+		newShowCommand(dockerCli),
 	)
 	return cmd
 }

cli/command/context/inspect.go

@@ -15,7 +15,7 @@ type inspectOptions struct {
 	refs   []string
 }
 
-// newInspectCommand creates a new cobra.Command for `docker image inspect`
+// newInspectCommand creates a new cobra.Command for `docker context inspect`
 func newInspectCommand(dockerCli command.Cli) *cobra.Command {
 	var opts inspectOptions
 

cli/command/context/show.go

@@ -0,0 +1,32 @@
+package context
+
+import (
+	"fmt"
+
+	"github.com/docker/cli/cli"
+	"github.com/docker/cli/cli/command"
+	"github.com/spf13/cobra"
+)
+
+// newShowCommand creates a new cobra.Command for `docker context sow`
+func newShowCommand(dockerCli command.Cli) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "show",
+		Short: "Print the name of the current context",
+		Args:  cli.NoArgs,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runShow(dockerCli)
+		},
+	}
+	return cmd
+}
+
+func runShow(dockerCli command.Cli) error {
+	context := dockerCli.CurrentContext()
+	metadata, err := dockerCli.ContextStore().GetMetadata(context)
+	if err != nil {
+		return err
+	}
+	fmt.Fprintln(dockerCli.Out(), metadata.Name)
+	return nil
+}

cli/command/context/show_test.go

@@ -0,0 +1,19 @@
+package context
+
+import (
+	"testing"
+
+	"gotest.tools/v3/assert"
+	"gotest.tools/v3/golden"
+)
+
+func TestShow(t *testing.T) {
+	cli := makeFakeCli(t)
+	createTestContext(t, cli, "current")
+	cli.SetCurrentContext("current")
+
+	cli.OutBuffer().Reset()
+	assert.NilError(t, runShow(cli))
+	golden.Assert(t, cli.OutBuffer().String(), "show.golden")
+
+}

cli/command/context/testdata/show.golden

@@ -0,0 +1 @@
+current

docs/reference/commandline/context_show.md

@@ -0,0 +1,61 @@
+---
+title: "context show"
+description: "The context show command description and usage"
+keywords: "context, show"
+---
+
+# context show
+
+```markdown
+Usage:  docker context show
+
+Print the name of the current context
+```
+
+## Description
+
+Print the name of the current context, possibly set by `DOCKER_CONTEXT` environment
+variable or `--context` global option.
+
+## Examples
+
+### Print the current context
+
+The following example prints the currently used [`docker context`](context.md):
+
+```console
+$ docker context show'
+default
+```
+
+As an example, this output can be used to dynamically change your shell prompt
+to indicate your active context. The example below illustrates how this output
+could be used when using Bash as your shell.
+
+Declare a function to obtain the current context in your `~/.bashrc`, and set
+this command as your `PROMPT_COMMAND`
+
+```console
+function docker_context_prompt() {
+        PS1="context: $(docker context show)> "
+}
+
+PROMPT_COMMAND=docker_context_prompt
+```
+
+After reloading the `~/.bashrc`, the prompt now shows the currently selected
+`docker context`:
+
+```console
+$ source ~/.bashrc
+context: default> docker context create --docker host=unix:///var/run/docker.sock my-context
+my-context
+Successfully created context "my-context"
+context: default> docker context use my-context
+my-context
+Current context is now "my-context"
+context: my-context> docker context use default
+default
+Current context is now "default"
+context: default>
+```

docs/reference/commandline/version.md

@@ -76,47 +76,3 @@ $ docker version --format '{{json .}}'
 
 {"Client":{"Platform":{"Name":"Docker Engine - Community"},"Version":"19.03.8","ApiVersion":"1.40","DefaultAPIVersion":"1.40","GitCommit":"afacb8b","GoVersion":"go1.12.17","Os":"darwin","Arch":"amd64","BuildTime":"Wed Mar 11 01:21:11 2020","Experimental":true},"Server":{"Platform":{"Name":"Docker Engine - Community"},"Components":[{"Name":"Engine","Version":"19.03.8","Details":{"ApiVersion":"1.40","Arch":"amd64","BuildTime":"Wed Mar 11 01:29:16 2020","Experimental":"true","GitCommit":"afacb8b","GoVersion":"go1.12.17","KernelVersion":"4.19.76-linuxkit","MinAPIVersion":"1.12","Os":"linux"}},{"Name":"containerd","Version":"v1.2.13","Details":{"GitCommit":"7ad184331fa3e55e52b890ea95e65ba581ae3429"}},{"Name":"runc","Version":"1.0.0-rc10","Details":{"GitCommit":"dc9208a3303feef5b3839f4323d9beb36df0a9dd"}},{"Name":"docker-init","Version":"0.18.0","Details":{"GitCommit":"fec3683"}}],"Version":"19.03.8","ApiVersion":"1.40","MinAPIVersion":"1.12","GitCommit":"afacb8b","GoVersion":"go1.12.17","Os":"linux","Arch":"amd64","KernelVersion":"4.19.76-linuxkit","Experimental":true,"BuildTime":"2020-03-11T01:29:16.000000000+00:00"}}
 ```
-
-### Print the current context
-
-The following example prints the currently used [`docker context`](context.md):
-
-```console
-$ docker version --format='{{.Client.Context}}'
-default
-```
-
-As an example, this output can be used to dynamically change your shell prompt
-to indicate your active context. The example below illustrates how this output
-could be used when using Bash as your shell.
-
-Declare a function to obtain the current context in your `~/.bashrc`, and set
-this command as your `PROMPT_COMMAND`
-
-```console
-function docker_context_prompt() {
-        PS1="context: $(docker version --format='{{.Client.Context}}')> "
-}
-
-PROMPT_COMMAND=docker_context_prompt
-```
-
-After reloading the `~/.bashrc`, the prompt now shows the currently selected
-`docker context`:
-
-```console
-$ source ~/.bashrc
-context: default> docker context create --docker host=unix:///var/run/docker.sock my-context
-my-context
-Successfully created context "my-context"
-context: default> docker context use my-context
-my-context
-Current context is now "my-context"
-context: my-context> docker context use default
-default
-Current context is now "default"
-context: default>
-```
-
-Refer to the [`docker context` section](context.md) in the command line reference
-for more information about `docker context`.