Add cimfs differ and snapshotter

Details about CimFs project are discussed in #8346

Signed-off-by: Amit Barve <ambarve@microsoft.com>

vendor/github.com/fsnotify/fsnotify/fsnotify.go

@@ -1,18 +1,13 @@
+//go:build !plan9
+// +build !plan9
+
 // Package fsnotify provides a cross-platform interface for file system
 // notifications.
-//
-// Currently supported systems:
-//
-//	Linux 2.6.32+    via inotify
-//	BSD, macOS       via kqueue
-//	Windows          via ReadDirectoryChangesW
-//	illumos          via FEN
 package fsnotify
 
 import (
 	"errors"
 	"fmt"
-	"path/filepath"
 	"strings"
 )
 
@@ -38,52 +33,34 @@ type Op uint32
 // The operations fsnotify can trigger; see the documentation on [Watcher] for a
 // full description, and check them with [Event.Has].
 const (
-	// A new pathname was created.
 	Create Op = 1 << iota
-
-	// The pathname was written to; this does *not* mean the write has finished,
-	// and a write can be followed by more writes.
 	Write
-
-	// The path was removed; any watches on it will be removed. Some "remove"
-	// operations may trigger a Rename if the file is actually moved (for
-	// example "remove to trash" is often a rename).
 	Remove
-
-	// The path was renamed to something else; any watched on it will be
-	// removed.
 	Rename
-
-	// File attributes were changed.
-	//
-	// It's generally not recommended to take action on this event, as it may
-	// get triggered very frequently by some software. For example, Spotlight
-	// indexing on macOS, anti-virus software, backup software, etc.
 	Chmod
 )
 
-// Common errors that can be reported.
+// Common errors that can be reported by a watcher
 var (
-	ErrNonExistentWatch = errors.New("fsnotify: can't remove non-existent watch")
-	ErrEventOverflow    = errors.New("fsnotify: queue or buffer overflow")
-	ErrClosed           = errors.New("fsnotify: watcher already closed")
+	ErrNonExistentWatch = errors.New("can't remove non-existent watcher")
+	ErrEventOverflow    = errors.New("fsnotify queue overflow")
 )
 
-func (o Op) String() string {
+func (op Op) String() string {
 	var b strings.Builder
-	if o.Has(Create) {
+	if op.Has(Create) {
 		b.WriteString("|CREATE")
 	}
-	if o.Has(Remove) {
+	if op.Has(Remove) {
 		b.WriteString("|REMOVE")
 	}
-	if o.Has(Write) {
+	if op.Has(Write) {
 		b.WriteString("|WRITE")
 	}
-	if o.Has(Rename) {
+	if op.Has(Rename) {
 		b.WriteString("|RENAME")
 	}
-	if o.Has(Chmod) {
+	if op.Has(Chmod) {
 		b.WriteString("|CHMOD")
 	}
 	if b.Len() == 0 {
@@ -93,7 +70,7 @@ func (o Op) String() string {
 }
 
 // Has reports if this operation has the given operation.
-func (o Op) Has(h Op) bool { return o&h != 0 }
+func (o Op) Has(h Op) bool { return o&h == h }
 
 // Has reports if this event has the given operation.
 func (e Event) Has(op Op) bool { return e.Op.Has(op) }
@@ -102,45 +79,3 @@ func (e Event) Has(op Op) bool { return e.Op.Has(op) }
 func (e Event) String() string {
 	return fmt.Sprintf("%-13s %q", e.Op.String(), e.Name)
 }
-
-type (
-	addOpt   func(opt *withOpts)
-	withOpts struct {
-		bufsize int
-	}
-)
-
-var defaultOpts = withOpts{
-	bufsize: 65536, // 64K
-}
-
-func getOptions(opts ...addOpt) withOpts {
-	with := defaultOpts
-	for _, o := range opts {
-		o(&with)
-	}
-	return with
-}
-
-// WithBufferSize sets the [ReadDirectoryChangesW] buffer size.
-//
-// This only has effect on Windows systems, and is a no-op for other backends.
-//
-// The default value is 64K (65536 bytes) which is the highest value that works
-// on all filesystems and should be enough for most applications, but if you
-// have a large burst of events it may not be enough. You can increase it if
-// you're hitting "queue or buffer overflow" errors ([ErrEventOverflow]).
-//
-// [ReadDirectoryChangesW]: https://learn.microsoft.com/en-gb/windows/win32/api/winbase/nf-winbase-readdirectorychangesw
-func WithBufferSize(bytes int) addOpt {
-	return func(opt *withOpts) { opt.bufsize = bytes }
-}
-
-// Check if this path is recursive (ends with "/..." or "\..."), and return the
-// path with the /... stripped.
-func recursivePath(path string) (string, bool) {
-	if filepath.Base(path) == "..." {
-		return filepath.Dir(path), true
-	}
-	return path, false
-}