Comment webhook's modified code and clone the repo if needed when setting the webhook

src/pusher/webhook/webhook.go

 	grafanaClient = client
 	deleteRemoved = delRemoved
 
-	repo, _, err = git.NewRepository(cfg.Git)
+	// Load the Git repository
+	repo, needsSync, err = git.NewRepository(cfg.Git)
 	if err != nil {
 		return err
 	}
 
+	// Synchronise the repository if needed.
+	if needsSync {
+		if err = repo.Sync(false); err != nil {
+			return err
+		}
+	}
+
+	// Initialise the webhook
 	hook := gitlab.New(&gitlab.Config{
 		Secret: cfg.Pusher.Config.Secret,
 	})
+	// Register the handler
 	hook.RegisterEvents(HandlePush, gitlab.PushEvents)
 
+	// Expose the webhook
 	return webhooks.Run(
 		hook,
 		cfg.Pusher.Config.Interface+":"+cfg.Pusher.Config.Port,
 			continue
 		}
 
+		// Copy added files' names
 		for _, addedFile := range commit.Added {
 			added = append(added, addedFile)
 		}
 
+		// Copy modified files' names
 		for _, modifiedFile := range commit.Modified {
 			modified = append(modified, modifiedFile)
 		}
 
+		// Copy removed files' names
 		for _, removedFile := range commit.Removed {
 			removed = append(removed, removedFile)
 		}
 	}
 
+	// Get the content of the removed files before pulling from the remote, because
+	// we won't be able to access them afterwards
 	if err = getFilesContents(removed, &contents, cfg); err != nil {
 		return
 	}
 
-	// Clone or pull the repository
+	// Synchronise the repository (i.e. pull from remote)
 	if err = repo.Sync(false); err != nil {
 		logrus.WithFields(logrus.Fields{
 			"error":      err,
 		return
 	}
 
+	// Get the content of the added files
 	if err = getFilesContents(added, &contents, cfg); err != nil {
 		return
 	}
 
+	// Get the content of the modified files
 	if err = getFilesContents(modified, &contents, cfg); err != nil {
 		return
 	}
 
+	// Remove the ignored files from the map
 	if err = common.FilterIgnored(&contents, cfg); err != nil {
 		return
 	}
 
+	// Push all added and modified dashboards to Grafana
 	common.PushFiles(added, contents, grafanaClient)
 	common.PushFiles(modified, contents, grafanaClient)
 
+	// If the user requested it, delete all dashboards that were removed
+	// from the repository.
 	if deleteRemoved {
 		common.DeleteDashboards(removed, contents, grafanaClient)
 	}
 	}
 }
 
+// getFilesContents takes a slice of files' names and a map mapping a file's name
+// to its content and appends to it the current content of all of the files for
+// which the name appears in the slice.
+// Returns an error if there was an issue reading a file.
 func getFilesContents(
 	filenames []string, contents *map[string][]byte, cfg *config.Config,
 ) (err error) {
+	// Iterate over files' names
 	for _, filename := range filenames {
-		// Read the file's content
+		// Compute the file's path
 		filePath := filepath.Join(cfg.Git.ClonePath, filename)
+		// Read the file's content
 		fileContent, err := ioutil.ReadFile(filePath)
 		if err != nil {
 			return err
 		}
 
+		// Append the content to the map
 		(*contents)[filename] = fileContent
 	}