Add polling as a fallback to native filesystem events in server watch

Fixes #8720
Fixes #6849
Fixes #7930

watcher/filenotify/fsnotify.go

@@ -0,0 +1,20 @@
+// Package filenotify is adapted from https://github.com/moby/moby/tree/master/pkg/filenotify, Apache-2.0 License.
+// Hopefully this can be replaced with an external package sometime in the future, see https://github.com/fsnotify/fsnotify/issues/9
+package filenotify
+
+import "github.com/fsnotify/fsnotify"
+
+// fsNotifyWatcher wraps the fsnotify package to satisfy the FileNotifier interface
+type fsNotifyWatcher struct {
+	*fsnotify.Watcher
+}
+
+// Events returns the fsnotify event channel receiver
+func (w *fsNotifyWatcher) Events() <-chan fsnotify.Event {
+	return w.Watcher.Events
+}
+
+// Errors returns the fsnotify error channel receiver
+func (w *fsNotifyWatcher) Errors() <-chan error {
+	return w.Watcher.Errors
+}