Add grouping for help message + streamlined help messages (#887)

* Add grouping for help message + streamlined help messages The top-level looks like kn is the command line interface for managing Knative Serving and Eventing objects Find more information about Knative at: https://knative.dev Serving Commands: service Manage Knative services revision Manage service revisions route List and show service routes Eventing Commands: source Manage event sources trigger Manage event triggers Other Commands: plugin Manage kn plugins completion Output shell completion code version Show the version of this client Use "kn <command> --help" for more information about a given command. Use "kn options" for a list of global command-line options (applies to all commands). The following changes have been applied: * Add CommandGroups for grouping commands together * Add flexible templating for the help messages * Moved global options to an own command ('kn options', much like 'kubectl options') * Aligned wording and typography of help messages These features has been highly inspired by kubectl grouping & help templating but has been considerably been stripped down to the needs of kn. Signed-off-by: Roland Huß <roland@ro14nd.de> * chore: Add missing file * Update pkg/templates/command_groups.go Co-authored-by: Matt Moore <mattmoor@vmware.com> * chore: Add some test for error messages * fix formatting * chore: Add test * moar tests * Update pkg/kn/commands/completion/completion.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/source/apiserver/delete.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/service/list.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/route/route.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/revision/delete.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/plugin/plugin.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/service/delete.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/revision/delete.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * Update pkg/kn/commands/service/delete.go Co-authored-by: Navid Shaikh <nshaikh@redhat.com> * regen docs * chore: Update conventions doc * Move some direct configuration of rootcmd to NewRootCommand() * Moved CaptureOutput to "test" package for reuse Co-authored-by: Matt Moore <mattmoor@vmware.com> Co-authored-by: Navid Shaikh <nshaikh@redhat.com>
2020-06-18 09:06:25 +02:00 · 2020-06-18 09:06:25 +02:00 · b916a5b3ed
parent c7426459be
commit b916a5b3ed
103 changed files with 1162 additions and 358 deletions
--- a/cmd/kn/main.go
+++ b/cmd/kn/main.go
@ -18,6 +18,7 @@ import (
 	"fmt"
 	"math/rand"
 	"os"
+	"regexp"
 	"strings"
 	"time"

@ -35,8 +36,8 @@ func init() {

 func main() {
 	err := run(os.Args[1:])
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+	if err != nil && len(os.Args) > 1 {
+		printError(err)
 		// This is the only point from where to exit when an error occurs
 		os.Exit(1)
 	}
@ -106,8 +107,14 @@ func stripFlags(args []string) ([]string, error) {
 				*commandsFound = append(*commandsFound, arg)
 			}
 		},
+		SilenceErrors: true,
+		SilenceUsage:  true,
 	}

+	// No help and usage functions to prin
+	extractCommand.SetHelpFunc(func(*cobra.Command, []string) {})
+	extractCommand.SetUsageFunc(func(*cobra.Command) error { return nil })
+
 	// Filter out --help and -h options to avoid special treatment which we don't
 	// need here
 	extractCommand.SetArgs(filterHelpOptions(args))
@ -172,10 +179,34 @@ func validateRootCommand(cmd *cobra.Command) error {
 	if err == nil && foundCmd.HasSubCommands() && len(innerArgs) > 0 {
 		argsWithoutFlags, err := stripFlags(innerArgs)
 		if len(argsWithoutFlags) > 0 || err != nil {
-			return errors.Errorf("unknown sub-command '%s' for '%s'. Available sub-commands: %s", innerArgs[0], foundCmd.Name(), strings.Join(root.ExtractSubCommandNames(foundCmd.Commands()), ", "))
+			return errors.Errorf("unknown sub-command '%s' for '%s'. Available sub-commands: %s", innerArgs[0], foundCmd.CommandPath(), strings.Join(root.ExtractSubCommandNames(foundCmd.Commands()), ", "))
 		}
 		// If no args where given (only flags), then fall through to execute the command itself, which leads to
 		// a more appropriate error message
 	}
 	return nil
 }
+
+// printError prints out any given error
+func printError(err error) {
+	fmt.Fprintf(os.Stderr, "Error: %s\n", cleanupErrorMessage(err.Error()))
+	fmt.Fprintf(os.Stderr, "Run '%s --help' for usage\n", extractCommandPathFromErrorMessage(err.Error(), os.Args[0]))
+}
+
+// extractCommandPathFromErrorMessage tries to extract the command name from an error message
+// by checking a pattern like 'kn service' in the error message. If not found, return the
+// base command name.
+func extractCommandPathFromErrorMessage(errorMsg string, arg0 string) string {
+	extractPattern := regexp.MustCompile(fmt.Sprintf("'(%s\\s.+?)'", arg0))
+	command := extractPattern.FindSubmatch([]byte(errorMsg))
+	if command != nil {
+		return string(command[1])
+	}
+	return arg0
+}
+
+// cleanupErrorMessage remove any redundance content of an error message
+func cleanupErrorMessage(msg string) string {
+	regexp := regexp.MustCompile("(?i)^error:\\s*")
+	return string(regexp.ReplaceAll([]byte(msg), []byte("")))
+}
--- a/cmd/kn/main_test.go
+++ b/cmd/kn/main_test.go
@ -15,14 +15,16 @@
 package main

 import (
+	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"testing"

 	"github.com/spf13/cobra"
 	"gotest.tools/assert"

-	"knative.dev/client/pkg/kn/commands"
+	"knative.dev/client/lib/test"
 	"knative.dev/client/pkg/kn/root"
 	"knative.dev/client/pkg/util"
 )
@ -226,6 +228,31 @@ func TestStripFlags(t *testing.T) {
 	}
 }

+func TestRunWithError(t *testing.T) {
+	data := []struct {
+		given    string
+		expected string
+	}{
+		{
+			"unknown sub-command blub",
+			"Error: unknown sub-command blub",
+		},
+		{
+			"error: unknown type blub",
+			"Error: unknown type blub",
+		},
+	}
+	for _, d := range data {
+		capture := test.CaptureOutput(t)
+		printError(errors.New(d.given))
+		stdOut, errOut := capture.Close()
+
+		assert.Equal(t, stdOut, "")
+		assert.Assert(t, strings.Contains(errOut, d.expected))
+		assert.Assert(t, util.ContainsAll(errOut, "Run", "--help", "usage"))
+	}
+}
+
 // Smoke test
 func TestRun(t *testing.T) {
 	oldArgs := os.Args
@ -234,9 +261,9 @@ func TestRun(t *testing.T) {
 		os.Args = oldArgs
 	})()

-	capture := commands.CaptureStdout(t)
+	capture := test.CaptureOutput(t)
 	err := run(os.Args[1:])
-	out := capture.Close()
+	out, _ := capture.Close()

 	assert.NilError(t, err)
 	assert.Assert(t, util.ContainsAllIgnoreCase(out, "version", "build", "git"))
--- a/conventions/cli.md
+++ b/conventions/cli.md
@ -51,6 +51,7 @@ be used:
 - `create` creates a resource.
 - `update` updates a resource.
 - `delete` deletes a resource.
+- `apply` for an idempotent "create-or-update", much like `kubetl apply`

 For a given resource, create and update should use the same arguments as much as
 possible and where it makes sense.
@ -84,6 +85,7 @@ Flags are used for specifying the input for `kn` commands and can have different
 characteristics:

 - They can be _mandatory_ or _optional_
+- Mandatory flags are mentioned in the `Use` attribute of a command like in `service NAME --image IMAGE` for `ServiceCommand`
 - Optional flags can have _default values_
 - Flag values can be _scalars_, _binary_, _lists_ or _maps_ (see below for
  details)
--- a/docs/cmd/kn.md
+++ b/docs/cmd/kn.md
@ -1,13 +1,12 @@
 ## kn

-Knative client
+kn manages Knative Serving and Eventing resources

 ### Synopsis

-Manage your Knative building blocks:
+kn is the command line interface for managing Knative Serving and Eventing resources

-* Serving: Manage your services and release new software to them.
-* Eventing: Manage event subscriptions and channels. Connect up event sources.
+ Find more information about Knative at: https://knative.dev

 ### Options

@ -21,11 +20,12 @@ Manage your Knative building blocks:
 ### SEE ALSO

 * [kn completion](kn_completion.md)	 - Output shell completion code
-* [kn plugin](kn_plugin.md)	 - Plugin command group
-* [kn revision](kn_revision.md)	 - Revision command group
-* [kn route](kn_route.md)	 - Route command group
-* [kn service](kn_service.md)	 - Service command group
-* [kn source](kn_source.md)	 - Event source command group
-* [kn trigger](kn_trigger.md)	 - Trigger command group
-* [kn version](kn_version.md)	 - Prints the client version
+* [kn options](kn_options.md)	 - Print the list of flags inherited by all commands
+* [kn plugin](kn_plugin.md)	 - Manage kn plugins
+* [kn revision](kn_revision.md)	 - Manage service revisions
+* [kn route](kn_route.md)	 - List and describe service routes
+* [kn service](kn_service.md)	 - Manage Knative services
+* [kn source](kn_source.md)	 - Manage event sources
+* [kn trigger](kn_trigger.md)	 - Manage event triggers
+* [kn version](kn_version.md)	 - Show the version of this client

--- a/docs/cmd/kn_completion.md
+++ b/docs/cmd/kn_completion.md
@ -13,7 +13,7 @@ Supported Shells:
 - zsh

 ```
-kn completion [SHELL] [flags]
+kn completion SHELL
 ```

 ### Examples
@ -44,5 +44,5 @@ kn completion [SHELL] [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources

--- a/docs/cmd/kn_options.md
+++ b/docs/cmd/kn_options.md
@ -0,0 +1,37 @@
+## kn options
+
+Print the list of flags inherited by all commands
+
+### Synopsis
+
+Print the list of flags inherited by all commands
+
+```
+kn options [flags]
+```
+
+### Examples
+
+```
+# Print flags inherited by all commands
+kn options
+```
+
+### Options
+
+```
+  -h, --help   help for options
+```
+
+### Options inherited from parent commands
+
+```
+      --config string       kn configuration file (default: ~/.config/kn/config.yaml)
+      --kubeconfig string   kubectl configuration file (default: ~/.kube/config)
+      --log-http            log http traffic
+```
+
+### SEE ALSO
+
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
+
--- a/docs/cmd/kn_plugin.md
+++ b/docs/cmd/kn_plugin.md
@ -1,16 +1,16 @@
 ## kn plugin

-Plugin command group
+Manage kn plugins

 ### Synopsis

-Provides utilities for interacting and managing with kn plugins.
+Manage kn plugins

 Plugins provide extended functionality that is not part of the core kn command-line distribution.
-Please refer to the documentation and examples for more information about how write your own plugins.
+Please refer to the documentation and examples for more information about how to write your own plugins.

 ```
-kn plugin [flags]
+kn plugin
 ```

 ### Options
@ -29,6 +29,6 @@ kn plugin [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
 * [kn plugin list](kn_plugin_list.md)	 - List plugins

--- a/docs/cmd/kn_plugin_list.md
+++ b/docs/cmd/kn_plugin_list.md
@ -10,10 +10,10 @@ Available plugins are those that are:
 - executable
 - begin with "kn-"
 - Kn's plugin directory
- Anywhere in the execution $PATH (if plugins.path-lookup config variable is enabled)
+- Anywhere in the execution $PATH (if plugins.path-lookup configuration variable is enabled)

 ```
-kn plugin list [flags]
+kn plugin list
 ```

 ### Options
@ -33,5 +33,5 @@ kn plugin list [flags]

 ### SEE ALSO

-* [kn plugin](kn_plugin.md)	 - Plugin command group
+* [kn plugin](kn_plugin.md)	 - Manage kn plugins

--- a/docs/cmd/kn_revision.md
+++ b/docs/cmd/kn_revision.md
@ -1,13 +1,13 @@
 ## kn revision

-Revision command group
+Manage service revisions

 ### Synopsis

-Revision command group
+Manage service revisions

 ```
-kn revision [flags]
+kn revision
 ```

 ### Options
@ -26,8 +26,8 @@ kn revision [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
-* [kn revision delete](kn_revision_delete.md)	 - Delete a revision.
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
+* [kn revision delete](kn_revision_delete.md)	 - Delete revisions
 * [kn revision describe](kn_revision_describe.md)	 - Show details of a revision
-* [kn revision list](kn_revision_list.md)	 - List available revisions.
+* [kn revision list](kn_revision_list.md)	 - List revisions

--- a/docs/cmd/kn_revision_delete.md
+++ b/docs/cmd/kn_revision_delete.md
@ -1,13 +1,13 @@
 ## kn revision delete

-Delete a revision.
+Delete revisions

 ### Synopsis

-Delete a revision.
+Delete revisions

 ```
-kn revision delete NAME [flags]
+kn revision delete NAME [NAME ...]
 ```

 ### Examples
@ -39,5 +39,5 @@ kn revision delete NAME [flags]

 ### SEE ALSO

-* [kn revision](kn_revision.md)	 - Revision command group
+* [kn revision](kn_revision.md)	 - Manage service revisions

--- a/docs/cmd/kn_revision_describe.md
+++ b/docs/cmd/kn_revision_describe.md
@ -7,7 +7,7 @@ Show details of a revision
 Show details of a revision

 ```
-kn revision describe NAME [flags]
+kn revision describe NAME
 ```

 ### Options
@ -31,5 +31,5 @@ kn revision describe NAME [flags]

 ### SEE ALSO

-* [kn revision](kn_revision.md)	 - Revision command group
+* [kn revision](kn_revision.md)	 - Manage service revisions

--- a/docs/cmd/kn_revision_list.md
+++ b/docs/cmd/kn_revision_list.md
@ -1,13 +1,13 @@
 ## kn revision list

-List available revisions.
+List revisions

 ### Synopsis

 List revisions for a given service.

 ```
-kn revision list [name] [flags]
+kn revision list
 ```

 ### Examples
@ -50,5 +50,5 @@ kn revision list [name] [flags]

 ### SEE ALSO

-* [kn revision](kn_revision.md)	 - Revision command group
+* [kn revision](kn_revision.md)	 - Manage service revisions

--- a/docs/cmd/kn_route.md
+++ b/docs/cmd/kn_route.md
@ -1,13 +1,13 @@
 ## kn route

-Route command group
+List and describe service routes

 ### Synopsis

-Route command group
+List and describe service routes

 ```
-kn route [flags]
+kn route
 ```

 ### Options
@ -26,7 +26,7 @@ kn route [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
 * [kn route describe](kn_route_describe.md)	 - Show details of a route
-* [kn route list](kn_route_list.md)	 - List available routes.
+* [kn route list](kn_route_list.md)	 - List routes

--- a/docs/cmd/kn_route_describe.md
+++ b/docs/cmd/kn_route_describe.md
@ -7,7 +7,7 @@ Show details of a route
 Show details of a route

 ```
-kn route describe NAME [flags]
+kn route describe NAME
 ```

 ### Options
@ -31,5 +31,5 @@ kn route describe NAME [flags]

 ### SEE ALSO

-* [kn route](kn_route.md)	 - Route command group
+* [kn route](kn_route.md)	 - List and describe service routes

--- a/docs/cmd/kn_route_list.md
+++ b/docs/cmd/kn_route_list.md
@ -1,13 +1,13 @@
 ## kn route list

-List available routes.
+List routes

 ### Synopsis

-List available routes.
+List routes

 ```
-kn route list NAME [flags]
+kn route list NAME
 ```

 ### Examples
@ -46,5 +46,5 @@ kn route list NAME [flags]

 ### SEE ALSO

-* [kn route](kn_route.md)	 - Route command group
+* [kn route](kn_route.md)	 - List and describe service routes

--- a/docs/cmd/kn_service.md
+++ b/docs/cmd/kn_service.md
@ -1,13 +1,13 @@
 ## kn service

-Service command group
+Manage Knative services

 ### Synopsis

-Service command group
+Manage Knative services

 ```
-kn service [flags]
+kn service
 ```

 ### Options
@ -26,11 +26,11 @@ kn service [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
-* [kn service create](kn_service_create.md)	 - Create a service.
-* [kn service delete](kn_service_delete.md)	 - Delete a service.
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
+* [kn service create](kn_service_create.md)	 - Create a service
+* [kn service delete](kn_service_delete.md)	 - Delete services
 * [kn service describe](kn_service_describe.md)	 - Show details of a service
-* [kn service export](kn_service_export.md)	 - Export a service.
-* [kn service list](kn_service_list.md)	 - List available services.
-* [kn service update](kn_service_update.md)	 - Update a service.
+* [kn service export](kn_service_export.md)	 - Export a service and its revisions
+* [kn service list](kn_service_list.md)	 - List services
+* [kn service update](kn_service_update.md)	 - Update a service

--- a/docs/cmd/kn_service_create.md
+++ b/docs/cmd/kn_service_create.md
@ -1,13 +1,13 @@
 ## kn service create

-Create a service.
+Create a service

 ### Synopsis

-Create a service.
+Create a service

 ```
-kn service create NAME --image IMAGE [flags]
+kn service create NAME --image IMAGE
 ```

 ### Examples
@ -101,5 +101,5 @@ kn service create NAME --image IMAGE [flags]

 ### SEE ALSO

-* [kn service](kn_service.md)	 - Service command group
+* [kn service](kn_service.md)	 - Manage Knative services

--- a/docs/cmd/kn_service_delete.md
+++ b/docs/cmd/kn_service_delete.md
@ -1,13 +1,13 @@
 ## kn service delete

-Delete a service.
+Delete services

 ### Synopsis

-Delete a service.
+Delete services

 ```
-kn service delete NAME [flags]
+kn service delete NAME [NAME ...]
 ```

 ### Examples
@ -46,5 +46,5 @@ kn service delete NAME [flags]

 ### SEE ALSO

-* [kn service](kn_service.md)	 - Service command group
+* [kn service](kn_service.md)	 - Manage Knative services

--- a/docs/cmd/kn_service_describe.md
+++ b/docs/cmd/kn_service_describe.md
@ -7,7 +7,7 @@ Show details of a service
 Show details of a service

 ```
-kn service describe NAME [flags]
+kn service describe NAME
 ```

 ### Options
@ -31,5 +31,5 @@ kn service describe NAME [flags]

 ### SEE ALSO

-* [kn service](kn_service.md)	 - Service command group
+* [kn service](kn_service.md)	 - Manage Knative services

--- a/docs/cmd/kn_service_export.md
+++ b/docs/cmd/kn_service_export.md
@ -1,13 +1,13 @@
 ## kn service export

-Export a service.
+Export a service and its revisions

 ### Synopsis

-Export a service.
+Export a service and its revisions

 ```
-kn service export NAME [flags]
+kn service export NAME
 ```

 ### Examples
@ -46,5 +46,5 @@ kn service export NAME [flags]

 ### SEE ALSO

-* [kn service](kn_service.md)	 - Service command group
+* [kn service](kn_service.md)	 - Manage Knative services

--- a/docs/cmd/kn_service_list.md
+++ b/docs/cmd/kn_service_list.md
@ -1,13 +1,13 @@
 ## kn service list

-List available services.
+List services

 ### Synopsis

-List available services.
+List services

 ```
-kn service list [name] [flags]
+kn service list
 ```

 ### Examples
@ -46,5 +46,5 @@ kn service list [name] [flags]

 ### SEE ALSO

-* [kn service](kn_service.md)	 - Service command group
+* [kn service](kn_service.md)	 - Manage Knative services

--- a/docs/cmd/kn_service_update.md
+++ b/docs/cmd/kn_service_update.md
@ -1,13 +1,13 @@
 ## kn service update

-Update a service.
+Update a service

 ### Synopsis

-Update a service.
+Update a service

 ```
-kn service update NAME [flags]
+kn service update NAME
 ```

 ### Examples
@ -91,5 +91,5 @@ kn service update NAME [flags]

 ### SEE ALSO

-* [kn service](kn_service.md)	 - Service command group
+* [kn service](kn_service.md)	 - Manage Knative services

--- a/docs/cmd/kn_source.md
+++ b/docs/cmd/kn_source.md
@ -1,13 +1,13 @@
 ## kn source

-Event source command group
+Manage event sources

 ### Synopsis

-Event source command group
+Manage event sources

 ```
-kn source [flags]
+kn source SOURCE|COMMAND
 ```

 ### Options
@ -26,10 +26,10 @@ kn source [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
-* [kn source apiserver](kn_source_apiserver.md)	 - Kubernetes API Server Event Source command group
-* [kn source binding](kn_source_binding.md)	 - Sink binding command group
-* [kn source list](kn_source_list.md)	 - List available sources
-* [kn source list-types](kn_source_list-types.md)	 - List available source types
-* [kn source ping](kn_source_ping.md)	 - Ping source command group
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
+* [kn source apiserver](kn_source_apiserver.md)	 - Manage Kubernetes api-server sources
+* [kn source binding](kn_source_binding.md)	 - Manage sink bindings
+* [kn source list](kn_source_list.md)	 - List event sources
+* [kn source list-types](kn_source_list-types.md)	 - List event source types
+* [kn source ping](kn_source_ping.md)	 - Manage ping sources

--- a/docs/cmd/kn_source_apiserver.md
+++ b/docs/cmd/kn_source_apiserver.md
@ -1,13 +1,13 @@
 ## kn source apiserver

-Kubernetes API Server Event Source command group
+Manage Kubernetes api-server sources

 ### Synopsis

-Kubernetes API Server Event Source command group
+Manage Kubernetes api-server sources

 ```
-kn source apiserver [flags]
+kn source apiserver COMMAND
 ```

 ### Options
@ -26,10 +26,10 @@ kn source apiserver [flags]

 ### SEE ALSO

-* [kn source](kn_source.md)	 - Event source command group
-* [kn source apiserver create](kn_source_apiserver_create.md)	 - Create an ApiServer source.
-* [kn source apiserver delete](kn_source_apiserver_delete.md)	 - Delete an ApiServer source.
-* [kn source apiserver describe](kn_source_apiserver_describe.md)	 - Show details of an ApiServer source
-* [kn source apiserver list](kn_source_apiserver_list.md)	 - List ApiServer sources.
-* [kn source apiserver update](kn_source_apiserver_update.md)	 - Update an ApiServer source.
+* [kn source](kn_source.md)	 - Manage event sources
+* [kn source apiserver create](kn_source_apiserver_create.md)	 - Create an api-server source
+* [kn source apiserver delete](kn_source_apiserver_delete.md)	 - Delete an api-server source
+* [kn source apiserver describe](kn_source_apiserver_describe.md)	 - Show details of an api-server source
+* [kn source apiserver list](kn_source_apiserver_list.md)	 - List api-server sources
+* [kn source apiserver update](kn_source_apiserver_update.md)	 - Update an api-server source

--- a/docs/cmd/kn_source_apiserver_create.md
+++ b/docs/cmd/kn_source_apiserver_create.md
@ -1,13 +1,13 @@
 ## kn source apiserver create

-Create an ApiServer source.
+Create an api-server source

 ### Synopsis

-Create an ApiServer source.
+Create an api-server source

 ```
-kn source apiserver create NAME --resource RESOURCE --service-account ACCOUNTNAME --sink SINK --mode MODE [flags]
+kn source apiserver create NAME --resource RESOURCE --sink SINK
 ```

 ### Examples
@ -43,5 +43,5 @@ kn source apiserver create NAME --resource RESOURCE --service-account ACCOUNTNAM

 ### SEE ALSO

-* [kn source apiserver](kn_source_apiserver.md)	 - Kubernetes API Server Event Source command group
+* [kn source apiserver](kn_source_apiserver.md)	 - Manage Kubernetes api-server sources

--- a/docs/cmd/kn_source_apiserver_delete.md
+++ b/docs/cmd/kn_source_apiserver_delete.md
@ -1,13 +1,13 @@
 ## kn source apiserver delete

-Delete an ApiServer source.
+Delete an api-server source

 ### Synopsis

-Delete an ApiServer source.
+Delete an api-server source

 ```
-kn source apiserver delete NAME [flags]
+kn source apiserver delete NAME
 ```

 ### Examples
@ -35,5 +35,5 @@ kn source apiserver delete NAME [flags]

 ### SEE ALSO

-* [kn source apiserver](kn_source_apiserver.md)	 - Kubernetes API Server Event Source command group
+* [kn source apiserver](kn_source_apiserver.md)	 - Manage Kubernetes api-server sources

--- a/docs/cmd/kn_source_apiserver_describe.md
+++ b/docs/cmd/kn_source_apiserver_describe.md
@ -1,13 +1,13 @@
 ## kn source apiserver describe

-Show details of an ApiServer source
+Show details of an api-server source

 ### Synopsis

-Show details of an ApiServer source
+Show details of an api-server source

 ```
-kn source apiserver describe NAME [flags]
+kn source apiserver describe NAME
 ```

 ### Examples
@ -36,5 +36,5 @@ kn source apiserver describe NAME [flags]

 ### SEE ALSO

-* [kn source apiserver](kn_source_apiserver.md)	 - Kubernetes API Server Event Source command group
+* [kn source apiserver](kn_source_apiserver.md)	 - Manage Kubernetes api-server sources

--- a/docs/cmd/kn_source_apiserver_list.md
+++ b/docs/cmd/kn_source_apiserver_list.md
@ -1,13 +1,13 @@
 ## kn source apiserver list

-List ApiServer sources.
+List api-server sources

 ### Synopsis

-List ApiServer sources.
+List api-server sources

 ```
-kn source apiserver list [flags]
+kn source apiserver list
 ```

 ### Examples
@ -43,5 +43,5 @@ kn source apiserver list [flags]

 ### SEE ALSO

-* [kn source apiserver](kn_source_apiserver.md)	 - Kubernetes API Server Event Source command group
+* [kn source apiserver](kn_source_apiserver.md)	 - Manage Kubernetes api-server sources

--- a/docs/cmd/kn_source_apiserver_update.md
+++ b/docs/cmd/kn_source_apiserver_update.md
@ -1,13 +1,13 @@
 ## kn source apiserver update

-Update an ApiServer source.
+Update an api-server source

 ### Synopsis

-Update an ApiServer source.
+Update an api-server source

 ```
-kn source apiserver update NAME --resource RESOURCE --service-account ACCOUNTNAME --sink SINK --mode MODE [flags]
+kn source apiserver update NAME
 ```

 ### Examples
@ -43,5 +43,5 @@ kn source apiserver update NAME --resource RESOURCE --service-account ACCOUNTNAM

 ### SEE ALSO

-* [kn source apiserver](kn_source_apiserver.md)	 - Kubernetes API Server Event Source command group
+* [kn source apiserver](kn_source_apiserver.md)	 - Manage Kubernetes api-server sources

--- a/docs/cmd/kn_source_binding.md
+++ b/docs/cmd/kn_source_binding.md
@ -1,13 +1,13 @@
 ## kn source binding

-Sink binding command group
+Manage sink bindings

 ### Synopsis

-Sink binding command group
+Manage sink bindings

 ```
-kn source binding [flags]
+kn source binding COMMAND
 ```

 ### Options
@ -26,10 +26,10 @@ kn source binding [flags]

 ### SEE ALSO

-* [kn source](kn_source.md)	 - Event source command group
-* [kn source binding create](kn_source_binding_create.md)	 - Create a sink binding.
-* [kn source binding delete](kn_source_binding_delete.md)	 - Delete a sink binding.
+* [kn source](kn_source.md)	 - Manage event sources
+* [kn source binding create](kn_source_binding_create.md)	 - Create a sink binding
+* [kn source binding delete](kn_source_binding_delete.md)	 - Delete a sink binding
 * [kn source binding describe](kn_source_binding_describe.md)	 - Show details of a sink binding
-* [kn source binding list](kn_source_binding_list.md)	 - List sink bindings.
-* [kn source binding update](kn_source_binding_update.md)	 - Update a sink binding.
+* [kn source binding list](kn_source_binding_list.md)	 - List sink bindings
+* [kn source binding update](kn_source_binding_update.md)	 - Update a sink binding

--- a/docs/cmd/kn_source_binding_create.md
+++ b/docs/cmd/kn_source_binding_create.md
@ -1,13 +1,13 @@
 ## kn source binding create

-Create a sink binding.
+Create a sink binding

 ### Synopsis

-Create a sink binding.
+Create a sink binding

 ```
-kn source binding create NAME --subject SUBJECT --sink SINK --ce-override KEY=VALUE [flags]
+kn source binding create NAME --subject SUBJECT --sink SINK
 ```

 ### Examples
@ -38,5 +38,5 @@ kn source binding create NAME --subject SUBJECT --sink SINK --ce-override KEY=VA

 ### SEE ALSO

-* [kn source binding](kn_source_binding.md)	 - Sink binding command group
+* [kn source binding](kn_source_binding.md)	 - Manage sink bindings

--- a/docs/cmd/kn_source_binding_delete.md
+++ b/docs/cmd/kn_source_binding_delete.md
@ -1,13 +1,13 @@
 ## kn source binding delete

-Delete a sink binding.
+Delete a sink binding

 ### Synopsis

-Delete a sink binding.
+Delete a sink binding

 ```
-kn source binding delete NAME [flags]
+kn source binding delete NAME
 ```

 ### Examples
@ -35,5 +35,5 @@ kn source binding delete NAME [flags]

 ### SEE ALSO

-* [kn source binding](kn_source_binding.md)	 - Sink binding command group
+* [kn source binding](kn_source_binding.md)	 - Manage sink bindings

--- a/docs/cmd/kn_source_binding_describe.md
+++ b/docs/cmd/kn_source_binding_describe.md
@ -7,7 +7,7 @@ Show details of a sink binding
 Show details of a sink binding

 ```
-kn source binding describe NAME [flags]
+kn source binding describe NAME
 ```

 ### Examples
@ -36,5 +36,5 @@ kn source binding describe NAME [flags]

 ### SEE ALSO

-* [kn source binding](kn_source_binding.md)	 - Sink binding command group
+* [kn source binding](kn_source_binding.md)	 - Manage sink bindings

--- a/docs/cmd/kn_source_binding_list.md
+++ b/docs/cmd/kn_source_binding_list.md
@ -1,13 +1,13 @@
 ## kn source binding list

-List sink bindings.
+List sink bindings

 ### Synopsis

-List sink bindings.
+List sink bindings

 ```
-kn source binding list [flags]
+kn source binding list
 ```

 ### Examples
@ -43,5 +43,5 @@ kn source binding list [flags]

 ### SEE ALSO

-* [kn source binding](kn_source_binding.md)	 - Sink binding command group
+* [kn source binding](kn_source_binding.md)	 - Manage sink bindings

--- a/docs/cmd/kn_source_binding_update.md
+++ b/docs/cmd/kn_source_binding_update.md
@ -1,13 +1,13 @@
 ## kn source binding update

-Update a sink binding.
+Update a sink binding

 ### Synopsis

-Update a sink binding.
+Update a sink binding

 ```
-kn source binding update NAME --subject SCHEDULE --sink SINK --ce-override OVERRIDE [flags]
+kn source binding update NAME
 ```

 ### Examples
@ -38,5 +38,5 @@ kn source binding update NAME --subject SCHEDULE --sink SINK --ce-override OVERR

 ### SEE ALSO

-* [kn source binding](kn_source_binding.md)	 - Sink binding command group
+* [kn source binding](kn_source_binding.md)	 - Manage sink bindings

--- a/docs/cmd/kn_source_list-types.md
+++ b/docs/cmd/kn_source_list-types.md
@ -1,23 +1,23 @@
 ## kn source list-types

-List available source types
+List event source types

 ### Synopsis

-List available source types
+List event source types

 ```
-kn source list-types [flags]
+kn source list-types
 ```

 ### Examples

 ```

-  # List available eventing source types
+  # List available event source types
  kn source list-types

-  # List available eventing source types in YAML format
+  # List available event source types in YAML format
  kn source list-types -o yaml
 ```

@ -42,5 +42,5 @@ kn source list-types [flags]

 ### SEE ALSO

-* [kn source](kn_source.md)	 - Event source command group
+* [kn source](kn_source.md)	 - Manage event sources

--- a/docs/cmd/kn_source_list.md
+++ b/docs/cmd/kn_source_list.md
@ -1,13 +1,13 @@
 ## kn source list

-List available sources
+List event sources

 ### Synopsis

-List available sources
+List event sources

 ```
-kn source list [flags]
+kn source list
 ```

 ### Examples
@ -47,5 +47,5 @@ kn source list [flags]

 ### SEE ALSO

-* [kn source](kn_source.md)	 - Event source command group
+* [kn source](kn_source.md)	 - Manage event sources

--- a/docs/cmd/kn_source_ping.md
+++ b/docs/cmd/kn_source_ping.md
@ -1,13 +1,13 @@
 ## kn source ping

-Ping source command group
+Manage ping sources

 ### Synopsis

-Ping source command group
+Manage ping sources

 ```
-kn source ping [flags]
+kn source ping COMMAND
 ```

 ### Options
@ -26,10 +26,10 @@ kn source ping [flags]

 ### SEE ALSO

-* [kn source](kn_source.md)	 - Event source command group
-* [kn source ping create](kn_source_ping_create.md)	 - Create a Ping source.
-* [kn source ping delete](kn_source_ping_delete.md)	 - Delete a Ping source.
-* [kn source ping describe](kn_source_ping_describe.md)	 - Show details of a Ping source
-* [kn source ping list](kn_source_ping_list.md)	 - List Ping sources.
-* [kn source ping update](kn_source_ping_update.md)	 - Update a Ping source.
+* [kn source](kn_source.md)	 - Manage event sources
+* [kn source ping create](kn_source_ping_create.md)	 - Create a ping source
+* [kn source ping delete](kn_source_ping_delete.md)	 - Delete a ping source
+* [kn source ping describe](kn_source_ping_describe.md)	 - Show details of a ping source
+* [kn source ping list](kn_source_ping_list.md)	 - List ping sources
+* [kn source ping update](kn_source_ping_update.md)	 - Update a ping source

--- a/docs/cmd/kn_source_ping_create.md
+++ b/docs/cmd/kn_source_ping_create.md
@ -1,13 +1,13 @@
 ## kn source ping create

-Create a Ping source.
+Create a ping source

 ### Synopsis

-Create a Ping source.
+Create a ping source

 ```
-kn source ping create NAME --schedule SCHEDULE --sink SINK --data DATA [flags]
+kn source ping create NAME
 ```

 ### Examples
@ -39,5 +39,5 @@ kn source ping create NAME --schedule SCHEDULE --sink SINK --data DATA [flags]

 ### SEE ALSO

-* [kn source ping](kn_source_ping.md)	 - Ping source command group
+* [kn source ping](kn_source_ping.md)	 - Manage ping sources

--- a/docs/cmd/kn_source_ping_delete.md
+++ b/docs/cmd/kn_source_ping_delete.md
@ -1,13 +1,13 @@
 ## kn source ping delete

-Delete a Ping source.
+Delete a ping source

 ### Synopsis

-Delete a Ping source.
+Delete a ping source

 ```
-kn source ping delete NAME [flags]
+kn source ping delete NAME
 ```

 ### Examples
@ -35,5 +35,5 @@ kn source ping delete NAME [flags]

 ### SEE ALSO

-* [kn source ping](kn_source_ping.md)	 - Ping source command group
+* [kn source ping](kn_source_ping.md)	 - Manage ping sources

--- a/docs/cmd/kn_source_ping_describe.md
+++ b/docs/cmd/kn_source_ping_describe.md
@ -1,13 +1,13 @@
 ## kn source ping describe

-Show details of a Ping source
+Show details of a ping source

 ### Synopsis

-Show details of a Ping source
+Show details of a ping source

 ```
-kn source ping describe NAME [flags]
+kn source ping describe NAME
 ```

 ### Examples
@ -36,5 +36,5 @@ kn source ping describe NAME [flags]

 ### SEE ALSO

-* [kn source ping](kn_source_ping.md)	 - Ping source command group
+* [kn source ping](kn_source_ping.md)	 - Manage ping sources

--- a/docs/cmd/kn_source_ping_list.md
+++ b/docs/cmd/kn_source_ping_list.md
@ -1,13 +1,13 @@
 ## kn source ping list

-List Ping sources.
+List ping sources

 ### Synopsis

-List Ping sources.
+List ping sources

 ```
-kn source ping list [flags]
+kn source ping list
 ```

 ### Examples
@ -43,5 +43,5 @@ kn source ping list [flags]

 ### SEE ALSO

-* [kn source ping](kn_source_ping.md)	 - Ping source command group
+* [kn source ping](kn_source_ping.md)	 - Manage ping sources

--- a/docs/cmd/kn_source_ping_update.md
+++ b/docs/cmd/kn_source_ping_update.md
@ -1,13 +1,13 @@
 ## kn source ping update

-Update a Ping source.
+Update a ping source

 ### Synopsis

-Update a Ping source.
+Update a ping source

 ```
-kn source ping update NAME --schedule SCHEDULE --sink SERVICE --data DATA [flags]
+kn source ping update NAME
 ```

 ### Examples
@ -39,5 +39,5 @@ kn source ping update NAME --schedule SCHEDULE --sink SERVICE --data DATA [flags

 ### SEE ALSO

-* [kn source ping](kn_source_ping.md)	 - Ping source command group
+* [kn source ping](kn_source_ping.md)	 - Manage ping sources

--- a/docs/cmd/kn_trigger.md
+++ b/docs/cmd/kn_trigger.md
@ -1,13 +1,13 @@
 ## kn trigger

-Trigger command group
+Manage event triggers

 ### Synopsis

-Trigger command group
+Manage event triggers

 ```
-kn trigger [flags]
+kn trigger
 ```

 ### Options
@ -26,10 +26,10 @@ kn trigger [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources
 * [kn trigger create](kn_trigger_create.md)	 - Create a trigger
-* [kn trigger delete](kn_trigger_delete.md)	 - Delete a trigger.
+* [kn trigger delete](kn_trigger_delete.md)	 - Delete a trigger
 * [kn trigger describe](kn_trigger_describe.md)	 - Show details of a trigger
-* [kn trigger list](kn_trigger_list.md)	 - List available triggers.
+* [kn trigger list](kn_trigger_list.md)	 - List triggers
 * [kn trigger update](kn_trigger_update.md)	 - Update a trigger

--- a/docs/cmd/kn_trigger_create.md
+++ b/docs/cmd/kn_trigger_create.md
@ -7,7 +7,7 @@ Create a trigger
 Create a trigger

 ```
-kn trigger create NAME --broker BROKER --sink SINK [flags]
+kn trigger create NAME --sink SINK
 ```

 ### Examples
@ -42,5 +42,5 @@ kn trigger create NAME --broker BROKER --sink SINK [flags]

 ### SEE ALSO

-* [kn trigger](kn_trigger.md)	 - Trigger command group
+* [kn trigger](kn_trigger.md)	 - Manage event triggers

--- a/docs/cmd/kn_trigger_delete.md
+++ b/docs/cmd/kn_trigger_delete.md
@ -1,13 +1,13 @@
 ## kn trigger delete

-Delete a trigger.
+Delete a trigger

 ### Synopsis

-Delete a trigger.
+Delete a trigger

 ```
-kn trigger delete NAME [flags]
+kn trigger delete NAME
 ```

 ### Examples
@ -35,5 +35,5 @@ kn trigger delete NAME [flags]

 ### SEE ALSO

-* [kn trigger](kn_trigger.md)	 - Trigger command group
+* [kn trigger](kn_trigger.md)	 - Manage event triggers

--- a/docs/cmd/kn_trigger_describe.md
+++ b/docs/cmd/kn_trigger_describe.md
@ -7,7 +7,7 @@ Show details of a trigger
 Show details of a trigger

 ```
-kn trigger describe NAME [flags]
+kn trigger describe NAME
 ```

 ### Examples
@ -36,5 +36,5 @@ kn trigger describe NAME [flags]

 ### SEE ALSO

-* [kn trigger](kn_trigger.md)	 - Trigger command group
+* [kn trigger](kn_trigger.md)	 - Manage event triggers

--- a/docs/cmd/kn_trigger_list.md
+++ b/docs/cmd/kn_trigger_list.md
@ -1,13 +1,13 @@
 ## kn trigger list

-List available triggers.
+List triggers

 ### Synopsis

-List available triggers.
+List triggers

 ```
-kn trigger list [name] [flags]
+kn trigger list
 ```

 ### Examples
@ -43,5 +43,5 @@ kn trigger list [name] [flags]

 ### SEE ALSO

-* [kn trigger](kn_trigger.md)	 - Trigger command group
+* [kn trigger](kn_trigger.md)	 - Manage event triggers

--- a/docs/cmd/kn_trigger_update.md
+++ b/docs/cmd/kn_trigger_update.md
@ -7,7 +7,7 @@ Update a trigger
 Update a trigger

 ```
-kn trigger update NAME --filter KEY=VALUE --sink SINK [flags]
+kn trigger update NAME
 ```

 ### Examples
@ -46,5 +46,5 @@ kn trigger update NAME --filter KEY=VALUE --sink SINK [flags]

 ### SEE ALSO

-* [kn trigger](kn_trigger.md)	 - Trigger command group
+* [kn trigger](kn_trigger.md)	 - Manage event triggers

--- a/docs/cmd/kn_version.md
+++ b/docs/cmd/kn_version.md
@ -1,13 +1,13 @@
 ## kn version

-Prints the client version
+Show the version of this client

 ### Synopsis

-Prints the client version
+Show the version of this client

 ```
-kn version [flags]
+kn version
 ```

 ### Options
@ -27,5 +27,5 @@ kn version [flags]

 ### SEE ALSO

-* [kn](kn.md)	 - Knative client
+* [kn](kn.md)	 - kn manages Knative Serving and Eventing resources

--- a/lib/test/capture_output.go
+++ b/lib/test/capture_output.go
@ -0,0 +1,77 @@
+// Copyright 2020 The Knative Authors
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// OutputCapture allows to capture any text written to standard out or standard error
+// which is especially useful during testing.
+//
+// Call it like:
+//
+// capture := CaptureOutput(t)
+// doSomeActionThatWritesToStdOutAndStdErr()
+// stdOut, stdErr := capture.Close()
+//
+// CaptureOutpu() and capture.Close() should always come in pairs as Close() also
+// restores the old streams
+package test
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"gotest.tools/assert"
+)
+
+type OutputCapture struct {
+	outRead, outWrite     *os.File
+	errorRead, errorWrite *os.File
+	t                     *testing.T
+
+	oldStdout *os.File
+	oldStderr *os.File
+}
+
+// CaptureOutput sets up standard our and standard error to capture any
+// output which
+func CaptureOutput(t *testing.T) OutputCapture {
+	ret := OutputCapture{
+		oldStdout: os.Stdout,
+		oldStderr: os.Stderr,
+		t:         t,
+	}
+	var err error
+	ret.outRead, ret.outWrite, err = os.Pipe()
+	assert.NilError(t, err)
+	os.Stdout = ret.outWrite
+	ret.errorRead, ret.errorWrite, err = os.Pipe()
+	assert.NilError(t, err)
+	os.Stderr = ret.errorWrite
+	return ret
+}
+
+// Close return the output collected and restores the original standard out and error streams
+// (i.e. those that were present before the call to CaptureOutput).
+func (c OutputCapture) Close() (string, string) {
+	err := c.outWrite.Close()
+	assert.NilError(c.t, err)
+	err = c.errorWrite.Close()
+	assert.NilError(c.t, err)
+	outOutput, err := ioutil.ReadAll(c.outRead)
+	assert.NilError(c.t, err)
+	errOutput, err := ioutil.ReadAll(c.errorRead)
+	assert.NilError(c.t, err)
+	os.Stdout = c.oldStdout
+	os.Stderr = c.oldStderr
+	return string(outOutput), string(errOutput)
+}
--- a/pkg/kn/commands/completion/completion.go
+++ b/pkg/kn/commands/completion/completion.go
@ -15,9 +15,10 @@
 package completion

 import (
-	"fmt"
 	"os"

+	"github.com/pkg/errors"
+
 	"knative.dev/client/pkg/kn/commands"

 	"github.com/spf13/cobra"
@ -43,23 +44,23 @@ Supported Shells:
 // NewCompletionCommand implements shell auto-completion feature for Bash and Zsh
 func NewCompletionCommand(p *commands.KnParams) *cobra.Command {
 	return &cobra.Command{
-		Use:       "completion [SHELL]",
+		Use:       "completion SHELL",
 		Short:     "Output shell completion code",
 		Long:      desc,
 		ValidArgs: []string{"bash", "zsh"},
 		Example:   eg,
-		Run: func(cmd *cobra.Command, args []string) {
+		RunE: func(cmd *cobra.Command, args []string) error {
 			if len(args) == 1 {
 				switch args[0] {
 				case "bash":
-					cmd.Root().GenBashCompletion(os.Stdout)
+					return cmd.Root().GenBashCompletion(os.Stdout)
 				case "zsh":
-					cmd.Root().GenZshCompletion(os.Stdout)
+					return cmd.Root().GenZshCompletion(os.Stdout)
 				default:
-					fmt.Println("only supports 'bash' or 'zsh' shell completion")
+					return errors.New("'bash' or 'zsh' shell completion is supported")
 				}
 			} else {
-				fmt.Println("accepts one argument either 'bash' or 'zsh'")
+				return errors.New("Only one argument can be provided, either 'bash' or 'zsh'")
 			}
 		},
 	}
--- a/pkg/kn/commands/completion/completion_test.go
+++ b/pkg/kn/commands/completion/completion_test.go
@ -17,6 +17,7 @@ package completion
 import (
 	"testing"

+	"knative.dev/client/lib/test"
 	"knative.dev/client/pkg/kn/commands"
 	"knative.dev/client/pkg/util"

@ -28,31 +29,30 @@ func TestCompletionUsage(t *testing.T) {
 	completionCmd := NewCompletionCommand(&commands.KnParams{})
 	assert.Assert(t, util.ContainsAllIgnoreCase(completionCmd.Use, "completion"))
 	assert.Assert(t, util.ContainsAllIgnoreCase(completionCmd.Short, "completion", "shell"))
-	assert.Assert(t, completionCmd.RunE == nil)
+	assert.Assert(t, completionCmd.Run == nil)
+	assert.Assert(t, completionCmd.RunE != nil)
 }

 func TestCompletionGeneration(t *testing.T) {
 	for _, shell := range []string{"bash", "zsh"} {
 		completionCmd := NewCompletionCommand(&commands.KnParams{})
-		c := commands.CaptureStdout(t)
-		completionCmd.Run(&cobra.Command{}, []string{shell})
-		out := c.Close()
-		assert.Assert(t, out != "")
+		c := test.CaptureOutput(t)
+		err := completionCmd.RunE(&cobra.Command{}, []string{shell})
+		assert.NilError(t, err)
+		stdOut, stdErr := c.Close()
+		assert.Assert(t, stdErr == "")
+		assert.Assert(t, stdOut != "")
 	}
 }

 func TestCompletionNoArg(t *testing.T) {
 	completionCmd := NewCompletionCommand(&commands.KnParams{})
-	c := commands.CaptureStdout(t)
-	completionCmd.Run(&cobra.Command{}, []string{})
-	out := c.Close()
-	assert.Assert(t, util.ContainsAll(out, "bash", "zsh", "one", "argument"))
+	err := completionCmd.RunE(&cobra.Command{}, []string{})
+	assert.Assert(t, util.ContainsAll(err.Error(), "bash", "zsh", "one", "argument"))
 }

 func TestCompletionWrongArg(t *testing.T) {
 	completionCmd := NewCompletionCommand(&commands.KnParams{})
-	c := commands.CaptureStdout(t)
-	completionCmd.Run(&cobra.Command{}, []string{"sh"})
-	out := c.Close()
-	assert.Assert(t, util.ContainsAll(out, "bash", "zsh", "only", "supports"))
+	err := completionCmd.RunE(&cobra.Command{}, []string{"sh"})
+	assert.Assert(t, util.ContainsAll(err.Error(), "bash", "zsh", "support"))
 }
--- a/pkg/kn/commands/options/options.go
+++ b/pkg/kn/commands/options/options.go
@ -0,0 +1,50 @@
+// Copyright © 2020 The Knative Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package options
+
+import (
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+
+	"knative.dev/client/pkg/templates"
+)
+
+// NewCmdOptions implements the options command
+func NewOptionsCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "options",
+		Short: "Print the list of flags inherited by all commands",
+		Long:  "Print the list of flags inherited by all commands",
+		Example: `# Print flags inherited by all commands
+kn options`,
+		Run: func(cmd *cobra.Command, args []string) {
+			cmd.SetOut(cmd.OutOrStdout())
+			cmd.Usage()
+		},
+		// Be quiet
+		SilenceErrors: true,
+		SilenceUsage:  true,
+		// Allow all options
+		FParseErrWhitelist: cobra.FParseErrWhitelist{UnknownFlags: true},
+	}
+	cmd.SetFlagErrorFunc(func(c *cobra.Command, err error) error {
+		return errors.Errorf("%s for '%s'", err.Error(), c.CommandPath())
+	})
+	cmd.SetUsageFunc(templates.NewGlobalOptionsFunc())
+	cmd.SetHelpFunc(func(command *cobra.Command, args []string) {
+		templates.NewGlobalOptionsFunc()(command)
+	})
+	return cmd
+}
--- a/pkg/kn/commands/plugin/list.go
+++ b/pkg/kn/commands/plugin/list.go
@ -48,7 +48,7 @@ Available plugins are those that are:
 - executable
 - begin with "kn-"
 - Kn's plugin directory
- Anywhere in the execution $PATH (if plugins.path-lookup config variable is enabled)`,
+- Anywhere in the execution $PATH (if plugins.path-lookup configuration variable is enabled)`,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return listPlugins(cmd, plFlags)
 		},
--- a/pkg/kn/commands/plugin/plugin.go
+++ b/pkg/kn/commands/plugin/plugin.go
@ -23,11 +23,11 @@ import (
 func NewPluginCommand(p *commands.KnParams) *cobra.Command {
 	pluginCmd := &cobra.Command{
 		Use:   "plugin",
-		Short: "Plugin command group",
-		Long: `Provides utilities for interacting and managing with kn plugins.
+		Short: "Manage kn plugins",
+		Long: `Manage kn plugins

 Plugins provide extended functionality that is not part of the core kn command-line distribution.
-Please refer to the documentation and examples for more information about how write your own plugins.`,
+Please refer to the documentation and examples for more information about how to write your own plugins.`,
 	}

 	pluginCmd.AddCommand(NewPluginListCommand(p))
--- a/pkg/kn/commands/revision/delete.go
+++ b/pkg/kn/commands/revision/delete.go
@ -29,8 +29,8 @@ func NewRevisionDeleteCommand(p *commands.KnParams) *cobra.Command {
 	var waitFlags commands.WaitFlags

 	RevisionDeleteCommand := &cobra.Command{
-		Use:   "delete NAME",
-		Short: "Delete a revision.",
+		Use:   "delete NAME [NAME ...]",
+		Short: "Delete revisions",
 		Example: `
  # Delete a revision 'svc1-abcde' in default namespace
  kn revision delete svc1-abcde`,
--- a/pkg/kn/commands/revision/list.go
+++ b/pkg/kn/commands/revision/list.go
@ -38,8 +38,8 @@ func NewRevisionListCommand(p *commands.KnParams) *cobra.Command {
 	revisionListFlags := flags.NewListPrintFlags(RevisionListHandlers)

 	revisionListCommand := &cobra.Command{
-		Use:   "list [name]",
-		Short: "List available revisions.",
+		Use:   "list",
+		Short: "List revisions",
 		Long:  "List revisions for a given service.",
 		Example: `
  # List all revisions
--- a/pkg/kn/commands/revision/revision.go
+++ b/pkg/kn/commands/revision/revision.go
@ -24,7 +24,7 @@ import (
 func NewRevisionCommand(p *commands.KnParams) *cobra.Command {
 	revisionCmd := &cobra.Command{
 		Use:   "revision",
-		Short: "Revision command group",
+		Short: "Manage service revisions",
 	}
 	revisionCmd.AddCommand(NewRevisionListCommand(p))
 	revisionCmd.AddCommand(NewRevisionDescribeCommand(p))
--- a/pkg/kn/commands/route/list.go
+++ b/pkg/kn/commands/route/list.go
@ -32,7 +32,7 @@ func NewRouteListCommand(p *commands.KnParams) *cobra.Command {
 	routeListFlags := flags.NewListPrintFlags(RouteListHandlers)
 	routeListCommand := &cobra.Command{
 		Use:   "list NAME",
-		Short: "List available routes.",
+		Short: "List routes",
 		Example: `
  # List all routes
  kn route list
--- a/pkg/kn/commands/route/route.go
+++ b/pkg/kn/commands/route/route.go
@ -23,7 +23,7 @@ import (
 func NewRouteCommand(p *commands.KnParams) *cobra.Command {
 	routeCmd := &cobra.Command{
 		Use:   "route",
-		Short: "Route command group",
+		Short: "List and describe service routes",
 	}
 	routeCmd.AddCommand(NewRouteListCommand(p))
 	routeCmd.AddCommand(NewRouteDescribeCommand(p))
--- a/pkg/kn/commands/service/create.go
+++ b/pkg/kn/commands/service/create.go
@ -72,7 +72,7 @@ func NewServiceCreateCommand(p *commands.KnParams) *cobra.Command {

 	serviceCreateCommand := &cobra.Command{
 		Use:     "create NAME --image IMAGE",
-		Short:   "Create a service.",
+		Short:   "Create a service",
 		Example: create_example,
 		RunE: func(cmd *cobra.Command, args []string) (err error) {
 			if len(args) != 1 {
--- a/pkg/kn/commands/service/delete.go
+++ b/pkg/kn/commands/service/delete.go
@ -30,8 +30,8 @@ func NewServiceDeleteCommand(p *commands.KnParams) *cobra.Command {
 	var waitFlags commands.WaitFlags

 	serviceDeleteCommand := &cobra.Command{
-		Use:   "delete NAME",
-		Short: "Delete a service.",
+		Use:   "delete NAME [NAME ...]",
+		Short: "Delete services",
 		Example: `
  # Delete a service 'svc1' in default namespace
  kn service delete svc1
--- a/pkg/kn/commands/service/export.go
+++ b/pkg/kn/commands/service/export.go
@ -50,7 +50,7 @@ func NewServiceExportCommand(p *commands.KnParams) *cobra.Command {

 	command := &cobra.Command{
 		Use:   "export NAME",
-		Short: "Export a service.",
+		Short: "Export a service and its revisions",
 		Example: `
  # Export a service in YAML format
  kn service export foo -n bar -o yaml
--- a/pkg/kn/commands/service/list.go
+++ b/pkg/kn/commands/service/list.go
@ -31,8 +31,8 @@ func NewServiceListCommand(p *commands.KnParams) *cobra.Command {
 	serviceListFlags := flags.NewListPrintFlags(ServiceListHandlers)

 	serviceListCommand := &cobra.Command{
-		Use:   "list [name]",
-		Short: "List available services.",
+		Use:   "list",
+		Short: "List services",
 		Example: `
  # List all services
  kn service list
--- a/pkg/kn/commands/service/service.go
+++ b/pkg/kn/commands/service/service.go
@ -34,7 +34,7 @@ const (
 func NewServiceCommand(p *commands.KnParams) *cobra.Command {
 	serviceCmd := &cobra.Command{
 		Use:   "service",
-		Short: "Service command group",
+		Short: "Manage Knative services",
 	}
 	serviceCmd.AddCommand(NewServiceListCommand(p))
 	serviceCmd.AddCommand(NewServiceDescribeCommand(p))
--- a/pkg/kn/commands/service/update.go
+++ b/pkg/kn/commands/service/update.go
@ -55,8 +55,8 @@ func NewServiceUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var waitFlags commands.WaitFlags
 	var trafficFlags flags.Traffic
 	serviceUpdateCommand := &cobra.Command{
-		Use:     "update NAME [flags]",
-		Short:   "Update a service.",
+		Use:     "update NAME",
+		Short:   "Update a service",
 		Example: updateExample,
 		RunE: func(cmd *cobra.Command, args []string) (err error) {
 			if len(args) != 1 {
--- a/pkg/kn/commands/source/apiserver/apiserver.go
+++ b/pkg/kn/commands/source/apiserver/apiserver.go
@ -26,8 +26,8 @@ import (
 // NewAPIServerCommand for managing ApiServer source
 func NewAPIServerCommand(p *commands.KnParams) *cobra.Command {
 	apiServerSourceCmd := &cobra.Command{
-		Use:   "apiserver",
-		Short: "Kubernetes API Server Event Source command group",
+		Use:   "apiserver COMMAND",
+		Short: "Manage Kubernetes api-server sources",
 	}
 	apiServerSourceCmd.AddCommand(NewAPIServerCreateCommand(p))
 	apiServerSourceCmd.AddCommand(NewAPIServerUpdateCommand(p))
--- a/pkg/kn/commands/source/apiserver/create.go
+++ b/pkg/kn/commands/source/apiserver/create.go
@ -32,8 +32,8 @@ func NewAPIServerCreateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "create NAME --resource RESOURCE --service-account ACCOUNTNAME --sink SINK --mode MODE",
-		Short: "Create an ApiServer source.",
+		Use:   "create NAME --resource RESOURCE --sink SINK",
+		Short: "Create an api-server source",
 		Example: `
  # Create an ApiServerSource 'k8sevents' which consumes Kubernetes events and sends message to service 'mysvc' as a cloudevent
  kn source apiserver create k8sevents --resource Event:v1 --service-account myaccountname --sink svc:mysvc`,
--- a/pkg/kn/commands/source/apiserver/delete.go
+++ b/pkg/kn/commands/source/apiserver/delete.go
@ -27,7 +27,7 @@ import (
 func NewAPIServerDeleteCommand(p *commands.KnParams) *cobra.Command {
 	deleteCommand := &cobra.Command{
 		Use:   "delete NAME",
-		Short: "Delete an ApiServer source.",
+		Short: "Delete an api-server source",
 		Example: `
  # Delete an ApiServerSource 'k8sevents' in default namespace
  kn source apiserver delete k8sevents`,
--- a/pkg/kn/commands/source/apiserver/describe.go
+++ b/pkg/kn/commands/source/apiserver/describe.go
@ -32,7 +32,7 @@ func NewAPIServerDescribeCommand(p *commands.KnParams) *cobra.Command {

 	apiServerDescribe := &cobra.Command{
 		Use:   "describe NAME",
-		Short: "Show details of an ApiServer source",
+		Short: "Show details of an api-server source",
 		Example: `
  # Describe an ApiServer source with name 'k8sevents'
  kn source apiserver describe k8sevents`,
--- a/pkg/kn/commands/source/apiserver/list.go
+++ b/pkg/kn/commands/source/apiserver/list.go
@ -29,7 +29,7 @@ func NewAPIServerListCommand(p *commands.KnParams) *cobra.Command {

 	listCommand := &cobra.Command{
 		Use:   "list",
-		Short: "List ApiServer sources.",
+		Short: "List api-server sources",
 		Example: `
  # List all ApiServer sources
  kn source apiserver list
--- a/pkg/kn/commands/source/apiserver/update.go
+++ b/pkg/kn/commands/source/apiserver/update.go
@ -32,8 +32,8 @@ func NewAPIServerUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "update NAME --resource RESOURCE --service-account ACCOUNTNAME --sink SINK --mode MODE",
-		Short: "Update an ApiServer source.",
+		Use:   "update NAME",
+		Short: "Update an api-server source",
 		Example: `
  # Update an ApiServerSource 'k8sevents' with different service account and sink service
  kn source apiserver update k8sevents --service-account newsa --sink svc:newsvc`,
--- a/pkg/kn/commands/source/binding/binding.go
+++ b/pkg/kn/commands/source/binding/binding.go
@ -32,8 +32,8 @@ import (
 // NewBindingCommand is the root command for all binding related commands
 func NewBindingCommand(p *commands.KnParams) *cobra.Command {
 	bindingCmd := &cobra.Command{
-		Use:   "binding",
-		Short: "Sink binding command group",
+		Use:   "binding COMMAND",
+		Short: "Manage sink bindings",
 	}
 	bindingCmd.AddCommand(NewBindingCreateCommand(p))
 	bindingCmd.AddCommand(NewBindingUpdateCommand(p))
--- a/pkg/kn/commands/source/binding/create.go
+++ b/pkg/kn/commands/source/binding/create.go
@ -32,8 +32,8 @@ func NewBindingCreateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "create NAME --subject SUBJECT --sink SINK --ce-override KEY=VALUE",
-		Short: "Create a sink binding.",
+		Use:   "create NAME --subject SUBJECT --sink SINK",
+		Short: "Create a sink binding",
 		Example: `
  # Create a sink binding which connects a deployment 'myapp' with a Knative service 'mysvc'
  kn source binding create my-binding --subject Deployment:apps/v1:myapp --sink svc:mysvc`,
--- a/pkg/kn/commands/source/binding/delete.go
+++ b/pkg/kn/commands/source/binding/delete.go
@ -26,7 +26,7 @@ import (
 func NewBindingDeleteCommand(p *commands.KnParams) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "delete NAME",
-		Short: "Delete a sink binding.",
+		Short: "Delete a sink binding",
 		Example: `
  # Delete a sink binding with name 'my-binding'
  kn source binding delete my-binding`,
--- a/pkg/kn/commands/source/binding/list.go
+++ b/pkg/kn/commands/source/binding/list.go
@ -28,7 +28,7 @@ func NewBindingListCommand(p *commands.KnParams) *cobra.Command {

 	cmd := &cobra.Command{
 		Use:   "list",
-		Short: "List sink bindings.",
+		Short: "List sink bindings",
 		Example: `
  # List all sink binidngs
  kn source binding list
--- a/pkg/kn/commands/source/binding/update.go
+++ b/pkg/kn/commands/source/binding/update.go
@ -32,8 +32,8 @@ func NewBindingUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "update NAME --subject SCHEDULE --sink SINK --ce-override OVERRIDE",
-		Short: "Update a sink binding.",
+		Use:   "update NAME",
+		Short: "Update a sink binding",
 		Example: `
  # Update the subject of a sink binding 'my-binding' to a new cronjob with label selector 'app=ping'  
  kn source binding update my-binding --subject cronjob:batch/v1beta1:app=ping"`,
--- a/pkg/kn/commands/source/list.go
+++ b/pkg/kn/commands/source/list.go
@ -41,7 +41,7 @@ func NewListCommand(p *commands.KnParams) *cobra.Command {
 	listFlags := flags.NewListPrintFlags(ListHandlers)
 	listCommand := &cobra.Command{
 		Use:     "list",
-		Short:   "List available sources",
+		Short:   "List event sources",
 		Example: listExample,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			namespace, err := p.GetNamespace(cmd)
--- a/pkg/kn/commands/source/list_types.go
+++ b/pkg/kn/commands/source/list_types.go
@ -28,12 +28,12 @@ func NewListTypesCommand(p *commands.KnParams) *cobra.Command {
 	listTypesFlags := flags.NewListPrintFlags(ListTypesHandlers)
 	listTypesCommand := &cobra.Command{
 		Use:   "list-types",
-		Short: "List available source types",
+		Short: "List event source types",
 		Example: `
-  # List available eventing source types
+  # List available event source types
  kn source list-types

-  # List available eventing source types in YAML format
+  # List available event source types in YAML format
  kn source list-types -o yaml`,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			namespace, err := p.GetNamespace(cmd)
--- a/pkg/kn/commands/source/ping/create.go
+++ b/pkg/kn/commands/source/ping/create.go
@ -32,8 +32,8 @@ func NewPingCreateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "create NAME --schedule SCHEDULE --sink SINK --data DATA",
-		Short: "Create a Ping source.",
+		Use:   "create NAME",
+		Short: "Create a ping source",
 		Example: `
  # Create a Ping source 'my-ping' which fires every two minutes and sends '{ value: "hello" }' to service 'mysvc' as a cloudevent
  kn source ping create my-ping --schedule "*/2 * * * *" --data '{ value: "hello" }' --sink svc:mysvc`,
--- a/pkg/kn/commands/source/ping/delete.go
+++ b/pkg/kn/commands/source/ping/delete.go
@ -26,7 +26,7 @@ import (
 func NewPingDeleteCommand(p *commands.KnParams) *cobra.Command {
 	pingDeleteCommand := &cobra.Command{
 		Use:   "delete NAME",
-		Short: "Delete a Ping source.",
+		Short: "Delete a ping source",
 		Example: `
  # Delete a Ping source 'my-ping'
  kn source ping delete my-ping`,
--- a/pkg/kn/commands/source/ping/describe.go
+++ b/pkg/kn/commands/source/ping/describe.go
@ -32,7 +32,7 @@ func NewPingDescribeCommand(p *commands.KnParams) *cobra.Command {

 	pingDescribe := &cobra.Command{
 		Use:   "describe NAME",
-		Short: "Show details of a Ping source",
+		Short: "Show details of a ping source",
 		Example: `
  # Describe a Ping source with name 'myping'
  kn source ping describe myping`,
--- a/pkg/kn/commands/source/ping/list.go
+++ b/pkg/kn/commands/source/ping/list.go
@ -29,7 +29,7 @@ func NewPingListCommand(p *commands.KnParams) *cobra.Command {

 	listCommand := &cobra.Command{
 		Use:   "list",
-		Short: "List Ping sources.",
+		Short: "List ping sources",
 		Example: `
  # List all Ping sources
  kn source ping list
--- a/pkg/kn/commands/source/ping/ping.go
+++ b/pkg/kn/commands/source/ping/ping.go
@ -26,8 +26,8 @@ import (
 // NewPingCommand is the root command for all Ping source related commands
 func NewPingCommand(p *commands.KnParams) *cobra.Command {
 	pingImporterCmd := &cobra.Command{
-		Use:   "ping",
-		Short: "Ping source command group",
+		Use:   "ping COMMAND",
+		Short: "Manage ping sources",
 	}
 	pingImporterCmd.AddCommand(NewPingCreateCommand(p))
 	pingImporterCmd.AddCommand(NewPingDeleteCommand(p))
--- a/pkg/kn/commands/source/ping/update.go
+++ b/pkg/kn/commands/source/ping/update.go
@ -32,8 +32,8 @@ func NewPingUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "update NAME --schedule SCHEDULE --sink SERVICE --data DATA",
-		Short: "Update a Ping source.",
+		Use:   "update NAME",
+		Short: "Update a ping source",
 		Example: `
  # Update the schedule of a Ping source 'my-ping' to fire every minute
  kn source ping update my-ping --schedule "* * * * *"`,
--- a/pkg/kn/commands/source/source.go
+++ b/pkg/kn/commands/source/source.go
@ -25,8 +25,8 @@ import (

 func NewSourceCommand(p *commands.KnParams) *cobra.Command {
 	sourceCmd := &cobra.Command{
-		Use:   "source",
-		Short: "Event source command group",
+		Use:   "source SOURCE|COMMAND",
+		Short: "Manage event sources",
 	}
 	sourceCmd.AddCommand(NewListTypesCommand(p))
 	sourceCmd.AddCommand(NewListCommand(p))
--- a/pkg/kn/commands/testing_helper.go
+++ b/pkg/kn/commands/testing_helper.go
@ -16,12 +16,9 @@ package commands

 import (
 	"bytes"
-	"io/ioutil"
 	"os"
-	"testing"

 	"github.com/spf13/cobra"
-	"gotest.tools/assert"
 	"k8s.io/apimachinery/pkg/runtime"
 	clienttesting "k8s.io/client-go/testing"
 	servingv1fake "knative.dev/serving/pkg/client/clientset/versioned/typed/serving/v1/fake"
@ -93,35 +90,6 @@ func CreateDynamicTestKnCommand(cmd *cobra.Command, knParams *KnParams, objects

 }

-type StdoutCapture struct {
-	r, w *os.File
-	t    *testing.T
-
-	oldStdout *os.File
-}
-
-func CaptureStdout(t *testing.T) StdoutCapture {
-	ret := StdoutCapture{
-		oldStdout: os.Stdout,
-		t:         t,
-	}
-	var err error
-	ret.r, ret.w, err = os.Pipe()
-	assert.NilError(t, err)
-	os.Stdout = ret.w
-	return ret
-}
-
-// CaptureStdout collects the current content of os.Stdout
-func (c StdoutCapture) Close() string {
-	err := c.w.Close()
-	assert.NilError(c.t, err)
-	ret, err := ioutil.ReadAll(c.r)
-	assert.NilError(c.t, err)
-	os.Stdout = c.oldStdout
-	return string(ret)
-}
-
 // NewTestCommand can be used by tes
 func NewTestCommand(subCommand *cobra.Command, params *KnParams) *cobra.Command {
 	rootCmd := &cobra.Command{
--- a/pkg/kn/commands/testing_helper_test.go
+++ b/pkg/kn/commands/testing_helper_test.go
@ -20,6 +20,8 @@ import (

 	"github.com/spf13/cobra"
 	"gotest.tools/assert"
+
+	"knative.dev/client/lib/test"
 )

 func TestCreateTestKnCommand(t *testing.T) {
@ -56,8 +58,9 @@ func TestCreateDynamicTestKnCommand(t *testing.T) {
 }

 func TestCaptureStdout(t *testing.T) {
-	c := CaptureStdout(t)
+	c := test.CaptureOutput(t)
 	fmt.Print("Hello World !")
-	out := c.Close()
-	assert.Equal(t, out, "Hello World !")
+	stdOut, stdErr := c.Close()
+	assert.Equal(t, stdErr, "")
+	assert.Equal(t, stdOut, "Hello World !")
 }
--- a/pkg/kn/commands/trigger/create.go
+++ b/pkg/kn/commands/trigger/create.go
@ -33,7 +33,7 @@ func NewTriggerCreateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "create NAME --broker BROKER --sink SINK",
+		Use:   "create NAME --sink SINK",
 		Short: "Create a trigger",
 		Example: `
  # Create a trigger 'mytrigger' to declare a subscription to events from default broker. The subscriber is service 'mysvc'
--- a/pkg/kn/commands/trigger/delete.go
+++ b/pkg/kn/commands/trigger/delete.go
@ -26,7 +26,7 @@ import (
 func NewTriggerDeleteCommand(p *commands.KnParams) *cobra.Command {
 	TriggerDeleteCommand := &cobra.Command{
 		Use:   "delete NAME",
-		Short: "Delete a trigger.",
+		Short: "Delete a trigger",
 		Example: `
  # Delete a trigger 'mytrigger' in default namespace
  kn trigger delete mytrigger`,
--- a/pkg/kn/commands/trigger/list.go
+++ b/pkg/kn/commands/trigger/list.go
@ -28,8 +28,8 @@ func NewTriggerListCommand(p *commands.KnParams) *cobra.Command {
 	triggerListFlags := flags.NewListPrintFlags(TriggerListHandlers)

 	triggerListCommand := &cobra.Command{
-		Use:   "list [name]",
-		Short: "List available triggers.",
+		Use:   "list",
+		Short: "List triggers",
 		Example: `
  # List all triggers
  kn trigger list
--- a/pkg/kn/commands/trigger/trigger.go
+++ b/pkg/kn/commands/trigger/trigger.go
@ -29,7 +29,7 @@ const (
 func NewTriggerCommand(p *commands.KnParams) *cobra.Command {
 	triggerCmd := &cobra.Command{
 		Use:   "trigger",
-		Short: "Trigger command group",
+		Short: "Manage event triggers",
 	}
 	triggerCmd.AddCommand(NewTriggerCreateCommand(p))
 	triggerCmd.AddCommand(NewTriggerUpdateCommand(p))
--- a/pkg/kn/commands/trigger/update.go
+++ b/pkg/kn/commands/trigger/update.go
@ -36,7 +36,7 @@ func NewTriggerUpdateCommand(p *commands.KnParams) *cobra.Command {
 	var sinkFlags flags.SinkFlags

 	cmd := &cobra.Command{
-		Use:   "update NAME --filter KEY=VALUE --sink SINK",
+		Use:   "update NAME",
 		Short: "Update a trigger",
 		Example: `
  # Update the filter which key is 'type' to value 'knative.dev.bar' in a trigger 'mytrigger'
--- a/pkg/kn/commands/version/version.go
+++ b/pkg/kn/commands/version/version.go
@ -50,7 +50,7 @@ type knVersion struct {
 func NewVersionCommand(p *commands.KnParams) *cobra.Command {
 	versionCmd := &cobra.Command{
 		Use:   "version",
-		Short: "Prints the client version",
+		Short: "Show the version of this client",
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if cmd.Flags().Changed("output") {
 				return printVersionMachineReadable(cmd)
--- a/pkg/kn/commands/version/version_test.go
+++ b/pkg/kn/commands/version/version_test.go
@ -25,6 +25,7 @@ import (
 	"sigs.k8s.io/yaml"

 	"knative.dev/client/pkg/kn/commands"
+	"knative.dev/client/pkg/util"
 )

 var versionOutputTemplate = `Version:      {{.Version}}
@ -73,7 +74,7 @@ func TestVersion(t *testing.T) {
 	t.Run("creates a VersionCommand", func(t *testing.T) {
 		setup()
 		assert.Equal(t, versionCmd.Use, "version")
-		assert.Equal(t, versionCmd.Short, "Prints the client version")
+		assert.Assert(t, util.ContainsAll(versionCmd.Short, "version"))
 		assert.Assert(t, versionCmd.RunE != nil)
 	})

--- a/pkg/kn/root/root.go
+++ b/pkg/kn/root/root.go
@ -17,17 +17,16 @@ package root
 import (
 	"flag"
 	"fmt"
-	"os"
 	"strings"

 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
-	"golang.org/x/crypto/ssh/terminal"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/oidc"

 	"knative.dev/client/pkg/kn/commands"
 	"knative.dev/client/pkg/kn/commands/completion"
+	"knative.dev/client/pkg/kn/commands/options"
 	"knative.dev/client/pkg/kn/commands/plugin"
 	"knative.dev/client/pkg/kn/commands/revision"
 	"knative.dev/client/pkg/kn/commands/route"
@ -37,6 +36,7 @@ import (
 	"knative.dev/client/pkg/kn/commands/version"
 	"knative.dev/client/pkg/kn/config"
 	"knative.dev/client/pkg/kn/flags"
+	"knative.dev/client/pkg/templates"
 )

 // NewRootCommand creates the default `kn` command with a default plugin handler
@ -46,19 +46,17 @@ func NewRootCommand() (*cobra.Command, error) {

 	rootCmd := &cobra.Command{
 		Use:   "kn",
-		Short: "Knative client",
-		Long: `Manage your Knative building blocks:
+		Short: "kn manages Knative Serving and Eventing resources",
+		Long: `kn is the command line interface for managing Knative Serving and Eventing resources

-* Serving: Manage your services and release new software to them.
-* Eventing: Manage event subscriptions and channels. Connect up event sources.`,
+ Find more information about Knative at: https://knative.dev`,

 		// Disable docs header
 		DisableAutoGenTag: true,

-		// Affects children as well
-		SilenceUsage: true,
-
-		// Prevents Cobra from dealing with errors as we deal with them in main.go
+		// Disable usage & error printing from cobra as we
+		// are handling all error output on our own
+		SilenceUsage:  true,
 		SilenceErrors: true,

 		// Validate our boolean configs
@ -77,18 +75,40 @@ func NewRootCommand() (*cobra.Command, error) {
 	rootCmd.PersistentFlags().StringVar(&p.KubeCfgPath, "kubeconfig", "", "kubectl configuration file (default: ~/.kube/config)")
 	flags.AddBothBoolFlags(rootCmd.PersistentFlags(), &p.LogHTTP, "log-http", "", false, "log http traffic")

-	// root child commands
-	rootCmd.AddCommand(service.NewServiceCommand(p))
-	rootCmd.AddCommand(revision.NewRevisionCommand(p))
-	rootCmd.AddCommand(plugin.NewPluginCommand(p))
-	rootCmd.AddCommand(route.NewRouteCommand(p))
-	rootCmd.AddCommand(completion.NewCompletionCommand(p))
-	rootCmd.AddCommand(version.NewVersionCommand(p))
-	rootCmd.AddCommand(source.NewSourceCommand(p))
-	rootCmd.AddCommand(trigger.NewTriggerCommand(p))
+	// Grouped commands
+	groups := templates.CommandGroups{
+		{
+			Header: "Serving Commands:",
+			Commands: []*cobra.Command{
+				service.NewServiceCommand(p),
+				revision.NewRevisionCommand(p),
+				route.NewRouteCommand(p),
+			},
+		},
+		{
+			Header: "Eventing Commands:",
+			Commands: []*cobra.Command{
+				source.NewSourceCommand(p),
+				trigger.NewTriggerCommand(p),
+			},
+		},
+		{
+			Header: "Other Commands:",
+			Commands: []*cobra.Command{
+				plugin.NewPluginCommand(p),
+				completion.NewCompletionCommand(p),
+				version.NewVersionCommand(p),
+			},
+		},
+	}
+	// Add all commands to the root command, flat
+	groups.AddTo(rootCmd)

 	// Initialize default `help` cmd early to prevent unknown command errors
-	rootCmd.InitDefaultHelpCmd()
+	groups.SetRootUsage(rootCmd)
+
+	// Add the "options" commands for showing all global options
+	rootCmd.AddCommand(options.NewOptionsCommand())

 	// Check that command groups can't execute and that leaf commands don't h
 	err := validateCommandStructure(rootCmd)
@ -96,8 +116,10 @@ func NewRootCommand() (*cobra.Command, error) {
 		return nil, err
 	}

-	// Wrap usage.
-	fitUsageMessageToTerminalWidth(rootCmd)
+	// Add some command context when flags can not be parsed
+	rootCmd.SetFlagErrorFunc(func(c *cobra.Command, err error) error {
+		return errors.Errorf("%s for '%s'", err.Error(), c.CommandPath())
+	})

 	// For glog parse error. TOO: Check why this is needed
 	flag.CommandLine.Parse([]string{})
@ -132,15 +154,6 @@ func validateCommandStructure(cmd *cobra.Command) error {
 	return nil
 }

-func fitUsageMessageToTerminalWidth(rootCmd *cobra.Command) {
-	width, _, err := terminal.GetSize(int(os.Stdout.Fd()))
-	if err == nil {
-		newUsage := strings.ReplaceAll(rootCmd.UsageTemplate(), "FlagUsages ",
-			fmt.Sprintf("FlagUsagesWrapped %d ", width))
-		rootCmd.SetUsageTemplate(newUsage)
-	}
-}
-
 // ExtractSubCommandNames extracts the names of all sub commands of a given command
 func ExtractSubCommandNames(cmds []*cobra.Command) []string {
 	var ret []string
--- a/pkg/kn/root/root_test.go
+++ b/pkg/kn/root/root_test.go
@ -15,6 +15,7 @@
 package root

 import (
+	"errors"
 	"strings"
 	"testing"

@ -30,7 +31,7 @@ func TestNewRootCommand(t *testing.T) {
 	assert.Assert(t, rootCmd != nil)

 	assert.Equal(t, rootCmd.Name(), "kn")
-	assert.Equal(t, rootCmd.Short, "Knative client")
+	assert.Assert(t, util.ContainsAll(rootCmd.Short, "Knative", "Serving", "Eventing"))
 	assert.Assert(t, util.ContainsAll(rootCmd.Long, "Knative", "Serving", "Eventing"))

 	assert.Assert(t, rootCmd.DisableAutoGenTag)
@ -43,6 +44,10 @@ func TestNewRootCommand(t *testing.T) {
 	assert.Assert(t, rootCmd.PersistentFlags().Lookup("kubeconfig") != nil)

 	assert.Assert(t, rootCmd.RunE == nil)
+
+	fErrorFunc := rootCmd.FlagErrorFunc()
+	err = fErrorFunc(rootCmd, errors.New("test"))
+	assert.Equal(t, err.Error(), "test for 'kn'")
 }

 func TestSubCommands(t *testing.T) {
--- a/pkg/templates/command_groups.go
+++ b/pkg/templates/command_groups.go
@ -0,0 +1,60 @@
+// Copyright © 2020 The Knative Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package templates
+
+import (
+	"github.com/spf13/cobra"
+)
+
+// A command group is for grouping together commands
+type CommandGroup struct {
+
+	// Title for command group shown in help/usage messages
+	Header string
+
+	// List of commands for this group
+	Commands []*cobra.Command
+}
+
+type CommandGroups []CommandGroup
+
+// Add all commands from this group slice to the given command
+func (g CommandGroups) AddTo(cmd *cobra.Command) {
+	for _, group := range g {
+		for _, sub := range group.Commands {
+			cmd.AddCommand(sub)
+		}
+	}
+}
+
+// SetRootUsage sets our own help and usage function messages to the root command
+func (g CommandGroups) SetRootUsage(rootCmd *cobra.Command) {
+	engine := &templateEngine{
+		RootCmd:       rootCmd,
+		CommandGroups: g,
+	}
+	setHelpFlagsToSubCommands(rootCmd)
+	rootCmd.SetUsageFunc(engine.usageFunc())
+	rootCmd.SetHelpFunc(engine.helpFunc())
+}
+
+func setHelpFlagsToSubCommands(parent *cobra.Command) {
+	for _, cmd := range parent.Commands() {
+		if cmd.HasSubCommands() {
+			setHelpFlagsToSubCommands(cmd)
+		}
+		cmd.DisableFlagsInUseLine = true
+	}
+}
--- a/pkg/templates/command_groups_test.go
+++ b/pkg/templates/command_groups_test.go
@ -0,0 +1,69 @@
+// Copyright © 2020 The Knative Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package templates
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/spf13/cobra"
+	"gotest.tools/assert"
+
+	"knative.dev/client/lib/test"
+	"knative.dev/client/pkg/util"
+)
+
+var groups = CommandGroups{
+	{
+		"header-1",
+		[]*cobra.Command{{Use: "c0"}, {Use: "c1"}},
+	},
+	{
+		"header-2",
+		[]*cobra.Command{{Use: "c2"}},
+	},
+}
+
+func TestAddTo(t *testing.T) {
+	rootCmd := &cobra.Command{Use: "root"}
+	groups.AddTo(rootCmd)
+
+	for idx, cmd := range rootCmd.Commands() {
+		assert.Equal(t, cmd.Name(), fmt.Sprintf("c%d", idx))
+	}
+}
+
+func TestSetUsage(t *testing.T) {
+	rootCmd := &cobra.Command{Use: "root", Short: "root", Run: func(cmd *cobra.Command, args []string) {}}
+	groups.AddTo(rootCmd)
+	groups.SetRootUsage(rootCmd)
+
+	for _, cmd := range rootCmd.Commands() {
+		assert.Assert(t, cmd.DisableFlagsInUseLine)
+	}
+
+	capture := test.CaptureOutput(t)
+	err := (rootCmd.UsageFunc())(rootCmd)
+	assert.NilError(t, err)
+	stdOut, stdErr := capture.Close()
+	assert.Equal(t, stdErr, "")
+	assert.Assert(t, util.ContainsAll(stdOut, "header-1", "header-2"))
+
+	capture = test.CaptureOutput(t)
+	(rootCmd.HelpFunc())(rootCmd, nil)
+	stdOut, stdErr = capture.Close()
+	assert.Equal(t, stdErr, "")
+	assert.Assert(t, util.ContainsAll(stdOut, "root", "header-1", "header-2"))
+}
--- a/Show More
+++ b/Show More