chore(general): cleanup "stale" error naming (kopia#3129)

Rename IsESTALE to IsStale to make it consistent with
the conventions in the Go ecosystem

Use errors.Is() instead of == comparison. It is more robust.

repo/blob/filesystem/filesystem_storage.go

@@ -52,7 +52,7 @@ func (fs *fsImpl) isRetriable(err error) bool {
 
 	err = errors.Cause(err)
 
-	if fs.osi.IsESTALE(err) {
+	if fs.osi.IsStale(err) {
 		// errors indicative of stale resource handle or invalid
 		// descriptors should not be retried
 		return false

repo/blob/filesystem/osinterface.go

@@ -17,6 +17,7 @@ type osInterface interface {
 	IsPathError(err error) bool
 	IsLinkError(err error) bool
 	IsPathSeparator(c byte) bool
+	IsStale(err error) bool
 	Remove(fname string) error
 	Rename(oldname, newname string) error
 	ReadDir(dirname string) ([]fs.DirEntry, error)
@@ -27,9 +28,6 @@ type osInterface interface {
 	Chtimes(fname string, atime, mtime time.Time) error
 	Geteuid() int
 	Chown(fname string, uid, gid int) error
-
-	// Errno
-	IsESTALE(err error) bool
 }
 
 type osReadFile interface {

repo/blob/filesystem/osinterface_realos_other.go

@@ -4,6 +4,6 @@
 package filesystem
 
 //nolint:revive
-func (realOS) IsESTALE(err error) bool {
+func (realOS) IsStale(err error) bool {
 	return false
 }

repo/blob/filesystem/osinterface_realos_unix.go

@@ -9,8 +9,6 @@ import (
 	"github.com/pkg/errors"
 )
 
-func (realOS) IsESTALE(err error) bool {
-	var errno syscall.Errno
-
-	return errors.As(err, &errno) && errno == syscall.ESTALE
+func (realOS) IsStale(err error) bool {
+	return errors.Is(err, syscall.ESTALE)
 }