vfs: Add VFS --links command line switch

This will be used to enable links support for the various mount engines
in a follow up commit.

vfs/vfs.go

@@ -242,6 +242,11 @@ func New(f fs.Fs, opt *vfscommon.Options) *VFS {
 		fs.Logf(f, "--vfs-cache-mode writes or full is recommended for this remote as it can't stream")
 	}
 
+	// Warn if we handle symlinks
+	if vfs.Opt.Links {
+		fs.Logf(f, "Symlinks support enabled")
+	}
+
 	// Pin the Fs into the cache so that when we use cache.NewFs
 	// with the same remote string we get this one. The Pin is
 	// removed when the vfs is finalized

vfs/vfscommon/options.go

@@ -44,6 +44,12 @@ var OptionsInfo = fs.Options{{
 	Default: false,
 	Help:    "Only allow read-only access",
 	Groups:  "VFS",
+}, {
+	Name:     "links",
+	Default:  false,
+	Help:     "Translate symlinks to/from regular files with a '" + fs.LinkSuffix + "' extension",
+	Groups:   "VFS",
+	ShortOpt: "l",
 }, {
 	Name:    "vfs_cache_mode",
 	Default: CacheModeOff,
@@ -165,6 +171,7 @@ type Options struct {
 	NoSeek             bool          `config:"no_seek"`        // don't allow seeking if set
 	NoChecksum         bool          `config:"no_checksum"`    // don't check checksums if set
 	ReadOnly           bool          `config:"read_only"`      // if set VFS is read only
+	Links              bool          `config:"links"`          // if set interpret link files
 	NoModTime          bool          `config:"no_modtime"`     // don't read mod times for files
 	DirCacheTime       fs.Duration   `config:"dir_cache_time"` // how long to consider directory listing cache valid
 	Refresh            bool          `config:"vfs_refresh"`    // refreshes the directory listing recursively on start