feat: add --userdata-file to device/update (#370)

Some preferential doc sting changes to highlight the ease of the recent
[changes to updating
always-pxe](a64058f)

Also C+V, C+V's the `--userdata-file` code from device/create to
device/update, making it easier to update complicated userdata formats
for devices in place.

```
$ bin/metal device update -i SOMEDEVICEUUID --userdata-file /tmp/my-cloud-init.mime
+--------------------------------------+----------+-------------+--------+
|                  ID                  | HOSTNAME |     OS      | STATE  |
+--------------------------------------+----------+-------------+--------+
| 9ffac3bb-4e04-466b-a786-b703fe52fa7f | h-01     | Custom iPXE | active |
+--------------------------------------+----------+-------------+--------+
```

Passed `make generate-docs` 🤷 ?

docs/metal_device_update.md

@@ -7,7 +7,7 @@ Updates a device.
 Updates the hostname of a device. Updates or adds a description, tags, userdata, custom data, and iPXE settings for an already provisioned device. Can also lock or unlock future changes to the device.
 
 ```
-metal device update -i <device_id> [-H <hostname>] [-d <description>] [--locked <boolean>] [-t <tags>] [-u <userdata>] [-c <customdata>] [-s <ipxe_script_url>] [--always-pxe=<true|false>] [flags]
+metal device update -i <device_id> [-H <hostname>] [-d <description>] [--locked <boolean>] [-t <tags>] [-u <userdata> | --userdata-file <filepath>] [-c <customdata>] [-s <ipxe_script_url>] [--always-pxe=<true|false>] [flags]
 ```
 
 ### Examples
@@ -20,16 +20,17 @@ metal device update -i <device_id> [-H <hostname>] [-d <description>] [--locked
 ### Options
 
 ```
-  -a, --always-pxe               Sets the device to always iPXE on reboot.
+  -a, --always-pxe               Updates the always_pxe toggle for the device (<true|false>).
   -c, --customdata string        Adds or updates custom data to be included with your device's metadata.
   -d, --description string       Adds or updates the description for the device.
   -h, --help                     help for update
   -H, --hostname string          The new hostname of the device.
   -i, --id string                The UUID of the device.
   -s, --ipxe-script-url string   Add or update the URL of the iPXE script.
-  -l, --locked                   Locks or unlocks the device for future changes.
+  -l, --locked                   Locks or unlocks the device for future changes (<true|false>).
   -t, --tags strings             Adds or updates the tags for the device --tags="tag1,tag2".
   -u, --userdata string          Adds or updates the userdata for the device.
+      --userdata-file string     Path to a userdata file for device initialization. Can not be used with --userdata.
 ```
 
 ### Options inherited from parent commands

internal/devices/update.go

@@ -24,6 +24,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"os"
 
 	metal "github.com/equinix-labs/metal-go/metal/v1"
 
@@ -35,6 +36,7 @@ func (c *Client) Update() *cobra.Command {
 		description   string
 		locked        bool
 		userdata      string
+		userdataFile  string
 		hostname      string
 		tags          []string
 		alwaysPXE     bool
@@ -44,7 +46,7 @@ func (c *Client) Update() *cobra.Command {
 	)
 	// updateDeviceCmd represents the updateDevice command
 	updateDeviceCmd := &cobra.Command{
-		Use:   `update -i <device_id> [-H <hostname>] [-d <description>] [--locked <boolean>] [-t <tags>] [-u <userdata>] [-c <customdata>] [-s <ipxe_script_url>] [--always-pxe=<true|false>]`,
+		Use:   `update -i <device_id> [-H <hostname>] [-d <description>] [--locked <boolean>] [-t <tags>] [-u <userdata> | --userdata-file <filepath>] [-c <customdata>] [-s <ipxe_script_url>] [--always-pxe=<true|false>]`,
 		Short: "Updates a device.",
 		Long:  "Updates the hostname of a device. Updates or adds a description, tags, userdata, custom data, and iPXE settings for an already provisioned device. Can also lock or unlock future changes to the device.",
 		Example: `  # Updates the hostname of a device:
@@ -62,6 +64,18 @@ func (c *Client) Update() *cobra.Command {
 				deviceUpdate.Description = &description
 			}
 
+			if userdata != "" && userdataFile != "" {
+				return fmt.Errorf("either userdata or userdata-file should be set")
+			}
+
+			if userdataFile != "" {
+				userdataRaw, readErr := os.ReadFile(userdataFile)
+				if readErr != nil {
+					return fmt.Errorf("could not read userdata-file: %w", readErr)
+				}
+				userdata = string(userdataRaw)
+			}
+
 			if userdata != "" {
 				deviceUpdate.Userdata = &userdata
 			}
@@ -108,9 +122,10 @@ func (c *Client) Update() *cobra.Command {
 	updateDeviceCmd.Flags().StringVarP(&hostname, "hostname", "H", "", "The new hostname of the device.")
 	updateDeviceCmd.Flags().StringVarP(&description, "description", "d", "", "Adds or updates the description for the device.")
 	updateDeviceCmd.Flags().StringVarP(&userdata, "userdata", "u", "", "Adds or updates the userdata for the device.")
-	updateDeviceCmd.Flags().BoolVarP(&locked, "locked", "l", false, "Locks or unlocks the device for future changes.")
+	updateDeviceCmd.Flags().StringVarP(&userdataFile, "userdata-file", "", "", "Path to a userdata file for device initialization. Can not be used with --userdata.")
+	updateDeviceCmd.Flags().BoolVarP(&locked, "locked", "l", false, "Locks or unlocks the device for future changes (<true|false>).")
 	updateDeviceCmd.Flags().StringSliceVarP(&tags, "tags", "t", []string{}, `Adds or updates the tags for the device --tags="tag1,tag2".`)
-	updateDeviceCmd.Flags().BoolVarP(&alwaysPXE, "always-pxe", "a", false, "Sets the device to always iPXE on reboot.")
+	updateDeviceCmd.Flags().BoolVarP(&alwaysPXE, "always-pxe", "a", false, "Updates the always_pxe toggle for the device (<true|false>).")
 	updateDeviceCmd.Flags().StringVarP(&ipxescripturl, "ipxe-script-url", "s", "", "Add or update the URL of the iPXE script.")
 	updateDeviceCmd.Flags().StringVarP(&customdata, "customdata", "c", "", "Adds or updates custom data to be included with your device's metadata.")
 	_ = updateDeviceCmd.MarkFlagRequired("id")