Add plugin CLI for interacting with the plugin catalog (#4911)

* Add 'plugin list' command

* Add 'plugin register' command

* Add 'plugin deregister' command

* Use a shared plugin helper

* Add 'plugin read' command

* Rename to plugin info

* Add base plugin for help text

* Fix arg ordering

* Add docs

* Rearrange to alphabetize

* Fix arg ordering in example

* Don't use "sudo" in command description

command/plugin_register_test.go

@@ -0,0 +1,151 @@
+package command
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/vault/api"
+	"github.com/mitchellh/cli"
+)
+
+func testPluginRegisterCommand(tb testing.TB) (*cli.MockUi, *PluginRegisterCommand) {
+	tb.Helper()
+
+	ui := cli.NewMockUi()
+	return ui, &PluginRegisterCommand{
+		BaseCommand: &BaseCommand{
+			UI: ui,
+		},
+	}
+}
+
+func TestPluginRegisterCommand_Run(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name string
+		args []string
+		out  string
+		code int
+	}{
+		{
+			"not_enough_args",
+			nil,
+			"Not enough arguments",
+			1,
+		},
+		{
+			"too_many_args",
+			[]string{"foo", "bar"},
+			"Too many arguments",
+			1,
+		},
+		{
+			"not_a_plugin",
+			[]string{"nope_definitely_never_a_plugin_nope"},
+			"",
+			2,
+		},
+	}
+
+	for _, tc := range cases {
+		tc := tc
+
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			client, closer := testVaultServer(t)
+			defer closer()
+
+			ui, cmd := testPluginRegisterCommand(t)
+			cmd.client = client
+
+			args := append([]string{"-sha256", "abcd1234"}, tc.args...)
+			code := cmd.Run(args)
+			if code != tc.code {
+				t.Errorf("expected %d to be %d", code, tc.code)
+			}
+
+			combined := ui.OutputWriter.String() + ui.ErrorWriter.String()
+			if !strings.Contains(combined, tc.out) {
+				t.Errorf("expected %q to contain %q", combined, tc.out)
+			}
+		})
+	}
+
+	t.Run("integration", func(t *testing.T) {
+		t.Parallel()
+
+		pluginDir, cleanup := testPluginDir(t)
+		defer cleanup(t)
+
+		client, _, closer := testVaultServerPluginDir(t, pluginDir)
+		defer closer()
+
+		pluginName := "my-plugin"
+		_, sha256Sum := testPluginCreate(t, pluginDir, pluginName)
+
+		ui, cmd := testPluginRegisterCommand(t)
+		cmd.client = client
+
+		code := cmd.Run([]string{
+			"-sha256", sha256Sum,
+			pluginName,
+		})
+		if exp := 0; code != exp {
+			t.Errorf("expected %d to be %d", code, exp)
+		}
+
+		expected := "Success! Registered plugin: my-plugin"
+		combined := ui.OutputWriter.String() + ui.ErrorWriter.String()
+		if !strings.Contains(combined, expected) {
+			t.Errorf("expected %q to contain %q", combined, expected)
+		}
+
+		resp, err := client.Sys().ListPlugins(&api.ListPluginsInput{})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		found := false
+		for _, p := range resp.Names {
+			if p == pluginName {
+				found = true
+			}
+		}
+		if !found {
+			t.Errorf("expected %q to be in %q", pluginName, resp.Names)
+		}
+	})
+
+	t.Run("communication_failure", func(t *testing.T) {
+		t.Parallel()
+
+		client, closer := testVaultServerBad(t)
+		defer closer()
+
+		ui, cmd := testPluginRegisterCommand(t)
+		cmd.client = client
+
+		code := cmd.Run([]string{
+			"-sha256", "abcd1234",
+			"my-plugin",
+		})
+		if exp := 2; code != exp {
+			t.Errorf("expected %d to be %d", code, exp)
+		}
+
+		expected := "Error registering plugin my-plugin:"
+		combined := ui.OutputWriter.String() + ui.ErrorWriter.String()
+		if !strings.Contains(combined, expected) {
+			t.Errorf("expected %q to contain %q", combined, expected)
+		}
+	})
+
+	t.Run("no_tabs", func(t *testing.T) {
+		t.Parallel()
+
+		_, cmd := testPluginRegisterCommand(t)
+		assertNoTabs(t, cmd)
+	})
+}