vfstests: move functional tests from mountlib and make them work with VFS

The tests are now run for the mount commands and for the plain VFS.

This makes the tests much easier to debug when running with a VFS than
through a mount.

vfs/vfstest/os.go

@@ -0,0 +1,116 @@
+package vfstest
+
+import (
+	"io/ioutil"
+	"os"
+	"time"
+
+	"github.com/rclone/rclone/lib/file"
+	"github.com/rclone/rclone/vfs"
+)
+
+// Oser defines the things that the "os" package can do
+//
+// This covers what the VFS can do also
+type Oser interface {
+	Chtimes(name string, atime time.Time, mtime time.Time) error
+	Create(name string) (vfs.Handle, error)
+	Mkdir(name string, perm os.FileMode) error
+	Open(name string) (vfs.Handle, error)
+	OpenFile(name string, flags int, perm os.FileMode) (fd vfs.Handle, err error)
+	ReadDir(dirname string) ([]os.FileInfo, error)
+	ReadFile(filename string) (b []byte, err error)
+	Remove(name string) error
+	Rename(oldName, newName string) error
+	Stat(path string) (os.FileInfo, error)
+}
+
+// realOs is an implementation of Oser backed by the "os" package
+type realOs struct {
+}
+
+// realOsFile is an implementation of vfs.Handle
+type realOsFile struct {
+	*os.File
+}
+
+// Flush
+func (f realOsFile) Flush() error {
+	return nil
+}
+
+// Release
+func (f realOsFile) Release() error {
+	return f.File.Close()
+}
+
+// Node
+func (f realOsFile) Node() vfs.Node {
+	return nil
+}
+
+// Chtimes
+func (r realOs) Chtimes(name string, atime time.Time, mtime time.Time) error {
+	return os.Chtimes(name, atime, mtime)
+}
+
+// Create
+func (r realOs) Create(name string) (vfs.Handle, error) {
+	fd, err := file.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+	if err != nil {
+		return nil, err
+	}
+	return realOsFile{File: fd}, err
+}
+
+// Mkdir
+func (r realOs) Mkdir(name string, perm os.FileMode) error {
+	return os.Mkdir(name, perm)
+}
+
+// Open
+func (r realOs) Open(name string) (vfs.Handle, error) {
+	fd, err := os.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	return realOsFile{File: fd}, err
+}
+
+// OpenFile
+func (r realOs) OpenFile(name string, flags int, perm os.FileMode) (vfs.Handle, error) {
+	fd, err := file.OpenFile(name, flags, perm)
+	if err != nil {
+		return nil, err
+	}
+	return realOsFile{File: fd}, err
+}
+
+// ReadDir
+func (r realOs) ReadDir(dirname string) ([]os.FileInfo, error) {
+	return ioutil.ReadDir(dirname)
+}
+
+// ReadFile
+func (r realOs) ReadFile(filename string) (b []byte, err error) {
+	return ioutil.ReadFile(filename)
+}
+
+// Remove
+func (r realOs) Remove(name string) error {
+	return os.Remove(name)
+}
+
+// Rename
+func (r realOs) Rename(oldName, newName string) error {
+	return os.Rename(oldName, newName)
+}
+
+// Stat
+func (r realOs) Stat(path string) (os.FileInfo, error) {
+	return os.Stat(path)
+}
+
+// Check interfaces
+var _ Oser = &realOs{}
+var _ vfs.Handle = &realOsFile{}