add update command

Author: adarshm11

README.md

@@ -95,3 +95,9 @@ Run eslint --fix on running containers (Clark and SCE-discord-bot only):
 sce lint <project>
 ```
 Make sure the project is running with `sce run` first.
+
+### Update
+Update the SCE CLI to the latest version. Runs the appropriate install script for your platform:
+```
+sce update
+```

go/cmd/update.go

@@ -0,0 +1,39 @@
+package cmd
+
+import (
+	"os"
+	"os/exec"
+	"runtime"
+
+	"github.com/spf13/cobra"
+)
+
+const (
+	unixInstallURL    = "https://raw.githubusercontent.com/SCE-Development/SCE-CLI/master/go/install.sh"
+	windowsInstallURL = "https://raw.githubusercontent.com/SCE-Development/SCE-CLI/master/go/install.ps1"
+)
+
+var updateCmd = &cobra.Command{
+	Use:   "update",
+	Short: "Update the SCE CLI to the latest version",
+	Args:  cobra.NoArgs,
+	Run: func(cmd *cobra.Command, args []string) {
+		var c *exec.Cmd
+		if runtime.GOOS == "windows" {
+			c = exec.Command("powershell", "-Command",
+				"Invoke-WebRequest -Uri \""+windowsInstallURL+"\" -UseBasicParsing | Invoke-Expression")
+		} else {
+			c = exec.Command("sh", "-c", "curl -sSL "+unixInstallURL+" | sh")
+		}
+		c.Stdout = os.Stdout
+		c.Stderr = os.Stderr
+		c.Stdin = os.Stdin
+		if err := c.Run(); err != nil {
+			os.Exit(1)
+		}
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(updateCmd)
+}