add automatic update checker

README.md

@@ -41,11 +41,11 @@ Create, control and connect to VirtualBox VM instances.
 
 ## Installation
 #### Automatic installation:
-To install or update for macos and linux:
+To install or **update** for macos and linux:
 ```shell script
 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/mhewedy/vermin/master/install.sh)"
 ```
-To install or update on windows (PowerShell):
+To install or **update** on windows (PowerShell):
 ```
 # Should run as Adminstarator
 C:\> iex ((New-Object System.Net.WebClient).DownloadString('https://raw.githubusercontent.com/mhewedy/vermin/master/install.ps1'))

cmd/root.go

@@ -34,6 +34,7 @@ $ vermin images
 Then you can create a vm using:
 $ vermin create <image>
 `,
+	PersistentPreRun: preRun,
 	// Uncomment the following line if your bare application
 	// has an action associated with it:
 	//	Run: func(cmd *cobra.Command, args []string) { },

cmd/util.go

@@ -2,6 +2,8 @@ package cmd
 
 import (
 	"fmt"
+	"github.com/mhewedy/vermin/config"
+	"github.com/spf13/cobra"
 	"os"
 )
 
@@ -11,3 +13,7 @@ func checkFilePath(path string) {
 		os.Exit(1)
 	}
 }
+
+func preRun(cmd *cobra.Command, args []string) {
+	config.CheckForUpdates(version)
+}

config/updater.go

@@ -0,0 +1,49 @@
+package config
+
+import (
+	"fmt"
+	"math/rand"
+	"net/http"
+	"strings"
+	"time"
+)
+
+const versionURL = "https://github.com/mhewedy/vermin/releases/latest"
+const updateURL = "https://github.com/mhewedy/vermin#Automatic-installation"
+
+var client = &http.Client{
+	CheckRedirect: func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	},
+}
+
+// CheckForUpdates checks for updates at random times
+func CheckForUpdates(currentVersion string) {
+	rand.Seed(time.Now().UnixNano())
+	r := rand.Intn(100)
+
+	if r == 0 {
+		req, err := http.NewRequest("HEAD", versionURL, nil)
+		if err != nil {
+			return
+		}
+
+		resp, err := client.Do(req)
+		if err != nil {
+			return
+		}
+		defer resp.Body.Close()
+
+		loc, err := resp.Location()
+		if err != nil {
+			return
+		}
+
+		s := strings.Split(loc.Path, "/")
+		newVersion := s[len(s)-1]
+
+		if currentVersion != newVersion {
+			fmt.Printf("\nNew version avaiable %s, check %s\n\n", newVersion, updateURL)
+		}
+	}
+}