vfs: add --vfs-refresh flag to read all the directories on start

Refreshes the directory listing recursively at VFS start time.

vfs/vfs.go

@@ -232,12 +232,26 @@ func New(f fs.Fs, opt *vfscommon.Options) *VFS {
 	// removed when the vfs is finalized
 	cache.PinUntilFinalized(f, vfs)
 
+	// Refresh the dircache if required
+	if vfs.Opt.Refresh {
+		go vfs.refresh()
+	}
+
 	// This can take some time so do it after the Pin
 	vfs.SetCacheMode(vfs.Opt.CacheMode)
 
 	return vfs
 }
 
+// refresh the directory cache for all directories
+func (vfs *VFS) refresh() {
+	fs.Debugf(vfs.f, "Refreshing VFS directory cache")
+	err := vfs.root.readDirTree()
+	if err != nil {
+		fs.Errorf(vfs.f, "Error refreshing VFS directory cache: %v", err)
+	}
+}
+
 // Stats returns info about the VFS
 func (vfs *VFS) Stats() (out rc.Params) {
 	out = make(rc.Params)

vfs/vfscommon/options.go

@@ -15,6 +15,7 @@ type Options struct {
 	ReadOnly           bool          // if set VFS is read only
 	NoModTime          bool          // don't read mod times for files
 	DirCacheTime       time.Duration // how long to consider directory listing cache valid
+	Refresh            bool          // refreshes the directory listing recursively on start
 	PollInterval       time.Duration
 	Umask              int
 	UID                uint32
@@ -44,6 +45,7 @@ var DefaultOpt = Options{
 	NoChecksum:         false,
 	NoSeek:             false,
 	DirCacheTime:       5 * 60 * time.Second,
+	Refresh:            false,
 	PollInterval:       time.Minute,
 	ReadOnly:           false,
 	Umask:              0,

vfs/vfsflags/vfsflags.go

@@ -22,6 +22,7 @@ func AddFlags(flagSet *pflag.FlagSet) {
 	flags.BoolVarP(flagSet, &Opt.NoChecksum, "no-checksum", "", Opt.NoChecksum, "Don't compare checksums on up/download", "VFS")
 	flags.BoolVarP(flagSet, &Opt.NoSeek, "no-seek", "", Opt.NoSeek, "Don't allow seeking in files", "VFS")
 	flags.DurationVarP(flagSet, &Opt.DirCacheTime, "dir-cache-time", "", Opt.DirCacheTime, "Time to cache directory entries for", "VFS")
+	flags.BoolVarP(flagSet, &Opt.Refresh, "vfs-refresh", "", Opt.Refresh, "Refreshes the directory cache recursively on start", "VFS")
 	flags.DurationVarP(flagSet, &Opt.PollInterval, "poll-interval", "", Opt.PollInterval, "Time to wait between polling for changes, must be smaller than dir-cache-time and only on supported remotes (set 0 to disable)", "VFS")
 	flags.BoolVarP(flagSet, &Opt.ReadOnly, "read-only", "", Opt.ReadOnly, "Only allow read-only access", "VFS")
 	flags.FVarP(flagSet, &Opt.CacheMode, "vfs-cache-mode", "", "Cache mode off|minimal|writes|full", "VFS")