link: allow creating public link to files and folders - closes #1562

fs/fs.go

@@ -328,6 +328,9 @@ type Features struct {
 	// as an optional interface
 	DirCacheFlush func()
 
+	// PublicLink generates a public link to the remote path (usually readable by anyone)
+	PublicLink func(remote string) (string, error)
+
 	// Put in to the remote path with the modTime given of the given size
 	//
 	// May create the object even if it returns an error - if so
@@ -443,6 +446,9 @@ func (ft *Features) Fill(f Fs) *Features {
 	if do, ok := f.(DirCacheFlusher); ok {
 		ft.DirCacheFlush = do.DirCacheFlush
 	}
+	if do, ok := f.(PublicLinker); ok {
+		ft.PublicLink = do.PublicLink
+	}
 	if do, ok := f.(PutUncheckeder); ok {
 		ft.PutUnchecked = do.PutUnchecked
 	}
@@ -642,6 +648,12 @@ type PutStreamer interface {
 	PutStream(in io.Reader, src ObjectInfo, options ...OpenOption) (Object, error)
 }
 
+// PublicLinker is an optional interface for Fs
+type PublicLinker interface {
+	// PublicLink generates a public link to the remote path (usually readable by anyone)
+	PublicLink(remote string) (string, error)
+}
+
 // MergeDirser is an option interface for Fs
 type MergeDirser interface {
 	// MergeDirs merges the contents of all the directories passed