Implement informed consent migration using the config file

internal/ooni/ooni.go

@@ -257,14 +257,24 @@ func InitDefaultConfig(home string) (*config.Config, error) {
 			if err != nil {
 				return nil, err
 			}
-			err = ioutil.WriteFile(
-				configPath,
-				data,
-				0644,
-			)
+			if err = ioutil.WriteFile(configPath, data, 0644); err != nil {
+				return nil, err
+			}
+			// If the user did the informed consent procedure in
+			// probe-legacy, migrate it over.
+			if utils.DidLegacyInformedConsent() {
+				c, err := config.ReadConfig(configPath)
 				if err != nil {
 					return nil, err
 				}
+				c.Lock()
+				c.InformedConsent = true
+				c.Unlock()
+				if err := c.Write(); err != nil {
+					return nil, err
+				}
+			}
+
 			return InitDefaultConfig(home)
 		}
 		return nil, err

internal/utils/paths.go

@@ -41,6 +41,13 @@ func DBDir(home string, name string) string {
 	return filepath.Join(home, "db", fmt.Sprintf("%s.sqlite3", name))
 }
 
+// FileExists returns true if the specified path exists and is a
+// regular file.
+func FileExists(path string) bool {
+	stat, err := os.Stat(path)
+	return err == nil && stat.Mode().IsRegular()
+}
+
 // ResultTimestamp is a windows friendly timestamp
 const ResultTimestamp = "2006-01-02T150405.999999999Z0700"
 
@@ -75,3 +82,17 @@ func GetOONIHome() (string, error) {
 	path := filepath.Join(home, ".ooniprobe")
 	return path, nil
 }
+
+// DidLegacyInformedConsent checks if the user did the informed consent procedure in probe-legacy
+func DidLegacyInformedConsent() bool {
+	home, err := homedir.Dir()
+	if err != nil {
+		return false
+	}
+
+	path := filepath.Join(filepath.Join(home, ".ooni"), "initialized")
+	if FileExists(path) {
+		return true
+	}
+	return false
+}