Handle existing clone paths that are not a Git repository

src/git/git.go

 package git
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
-	"strings"
 
 	"config"
 
 		return
 	}
 
+	// Check whether the clone path is a Git repository
+	var isRepo bool
+	if isRepo, err = dirExists(cfg.ClonePath + "/.git"); err != nil {
+		return
+	} else if exists && !isRepo {
+		err = fmt.Errorf(
+			"%s already exists but is not a Git repository",
+			cfg.ClonePath,
+		)
+
+		return
+	}
+
 	logrus.WithFields(logrus.Fields{
 		"repo":       cfg.User + "@" + cfg.URL,
 		"clone_path": cfg.ClonePath,