Add --format to docker service ls

This fix tries to improve the display of `docker service ls`
and adds `--format` flag to `docker service ls`.

In addition to `--format` flag, several other improvement:
1. Updates `docker stacks service`.
2. Adds `servicesFormat` to config file.

Related docs has been updated.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

docs/reference/commandline/cli.md

@@ -137,6 +137,13 @@ Docker's client uses this property. If this property is not set, the client
 falls back to the default table format. For a list of supported formatting
 directives, see the [**Formatting** section in the `docker plugin ls` documentation](plugin_ls.md)
 
+The property `servicesFormat` specifies the default format for `docker
+service ls` output. When the `--format` flag is not provided with the
+`docker service ls` command, Docker's client uses this property. If this
+property is not set, the client falls back to the default json format. For a
+list of supported formatting directives, see the
+[**Formatting** section in the `docker service ls` documentation](service_ls.md)
+
 The property `serviceInspectFormat` specifies the default format for `docker
 service inspect` output. When the `--format` flag is not provided with the
 `docker service inspect` command, Docker's client uses this property. If this
@@ -194,6 +201,7 @@ Following is a sample `config.json` file:
       "imagesFormat": "table {{.ID}}\\t{{.Repository}}\\t{{.Tag}}\\t{{.CreatedAt}}",
       "pluginsFormat": "table {{.ID}}\t{{.Name}}\t{{.Enabled}}",
       "statsFormat": "table {{.Container}}\t{{.CPUPerc}}\t{{.MemUsage}}",
+      "servicesFormat": "table {{.ID}}\t{{.Name}}\t{{.Mode}}",
       "serviceInspectFormat": "pretty",
       "detachKeys": "ctrl-e,e",
       "credsStore": "secretservice",

docs/reference/commandline/service_ls.md

@@ -24,9 +24,10 @@ Aliases:
   ls, list
 
 Options:
-  -f, --filter value   Filter output based on conditions provided
-      --help           Print usage
-  -q, --quiet          Only display IDs
+  -f, --filter filter   Filter output based on conditions provided
+      --format string   Pretty-print services using a Go template
+      --help            Print usage
+  -q, --quiet           Only display IDs
 ```
 
 This command when run targeting a manager, lists services are running in the
@@ -103,6 +104,34 @@ ID            NAME   MODE        REPLICAS  IMAGE
 0bcjwfh8ychr  redis  replicated  1/1       redis:3.0.6
 ```
 
+## Formatting
+
+The formatting options (`--format`) pretty-prints services output
+using a Go template.
+
+Valid placeholders for the Go template are listed below:
+
+Placeholder | Description
+------------|------------------------------------------------------------------------------------------
+`.ID`       | Service ID
+`.Name`     | Service name
+`.Mode`     | Service mode (replicated, global)
+`.Replicas` | Service replicas
+`.Image`    | Service image
+
+When using the `--format` option, the `service ls` command will either
+output the data exactly as the template declares or, when using the
+`table` directive, includes column headers as well.
+
+The following example uses a template without headers and outputs the
+`ID`, `Mode`, and `Replicas` entries separated by a colon for all services:
+
+```bash
+$ docker service ls --format "{{.ID}}: {{.Mode}} {{.Replicas}}"
+0zmvwuiu3vue: replicated 10/10
+fm6uf97exkul: global 5/5
+```
+
 ## Related information
 
 * [service create](service_create.md)

docs/reference/commandline/stack_services.md

@@ -22,9 +22,10 @@ Usage:	docker stack services [OPTIONS] STACK
 List the services in the stack
 
 Options:
-  -f, --filter value   Filter output based on conditions provided
-      --help           Print usage
-  -q, --quiet          Only display IDs
+  -f, --filter filter   Filter output based on conditions provided
+      --format string   Pretty-print services using a Go template
+      --help            Print usage
+  -q, --quiet           Only display IDs
 ```
 
 Lists the services that are running as part of the specified stack. This
@@ -62,6 +63,35 @@ The currently supported filters are:
 * name (`--filter name=myapp_web`)
 * label (`--filter label=key=value`)
 
+## Formatting
+
+The formatting options (`--format`) pretty-prints services output
+using a Go template.
+
+Valid placeholders for the Go template are listed below:
+
+Placeholder | Description
+------------|------------------------------------------------------------------------------------------
+`.ID`       | Service ID
+`.Name`     | Service name
+`.Mode`     | Service mode (replicated, global)
+`.Replicas` | Service replicas
+`.Image`    | Service image
+
+When using the `--format` option, the `stack services` command will either
+output the data exactly as the template declares or, when using the
+`table` directive, includes column headers as well.
+
+The following example uses a template without headers and outputs the
+`ID`, `Mode`, and `Replicas` entries separated by a colon for all services:
+
+```bash
+$ docker stack services --format "{{.ID}}: {{.Mode}} {{.Replicas}}"
+0zmvwuiu3vue: replicated 10/10
+fm6uf97exkul: global 5/5
+```
+
+
 ## Related information
 
 * [stack deploy](stack_deploy.md)