fs: add Directory Metadata flags for backends and interfaces

Add backend flags
- ReadDirMetadata
- WriteDirMetadata
- WriteDirSetModTime
- UserDirMetadata
- DirModTimeUpdatesOnWrite

Add Metadata/SetMetadata for directories.

Add MkdirMetadata optional feature

fs/features.go

@@ -29,6 +29,11 @@ type Features struct {
 	ReadMetadata             bool // can read metadata from objects
 	WriteMetadata            bool // can write metadata to objects
 	UserMetadata             bool // can read/write general purpose metadata
+	ReadDirMetadata          bool // can read metadata from directories (implements Directory.Metadata)
+	WriteDirMetadata         bool // can write metadata to directories (implements Directory.SetMetadata)
+	WriteDirSetModTime       bool // can write metadata to directories (implements Directory.SetModTime)
+	UserDirMetadata          bool // can read/write general purpose metadata to/from directories
+	DirModTimeUpdatesOnWrite bool // indicate writing files to a directory updates its modtime
 	FilterAware              bool // can make use of filters if provided for listing
 	PartialUploads           bool // uploaded file can appear incomplete on the fs while it's being uploaded
 	NoMultiThreading         bool // set if can't have multiplethreads on one download open
@@ -75,6 +80,15 @@ type Features struct {
 	// If destination exists then return fs.ErrorDirExists
 	DirMove func(ctx context.Context, src Fs, srcRemote, dstRemote string) error
 
+	// MkdirMetadata makes the directory passed in as dir.
+	//
+	// It shouldn't return an error if it already exists.
+	//
+	// If the metadata is not nil it is set.
+	//
+	// It returns the directory that was created.
+	MkdirMetadata func(ctx context.Context, dir string, metadata Metadata) (Directory, error)
+
 	// ChangeNotify calls the passed function with a path
 	// that has had changes. If the implementation
 	// uses polling, it should adhere to the given interval.
@@ -274,6 +288,9 @@ func (ft *Features) Fill(ctx context.Context, f Fs) *Features {
 	if do, ok := f.(DirMover); ok {
 		ft.DirMove = do.DirMove
 	}
+	if do, ok := f.(MkdirMetadataer); ok {
+		ft.MkdirMetadata = do.MkdirMetadata
+	}
 	if do, ok := f.(ChangeNotifier); ok {
 		ft.ChangeNotify = do.ChangeNotify
 	}
@@ -348,6 +365,11 @@ func (ft *Features) Mask(ctx context.Context, f Fs) *Features {
 	ft.ReadMetadata = ft.ReadMetadata && mask.ReadMetadata
 	ft.WriteMetadata = ft.WriteMetadata && mask.WriteMetadata
 	ft.UserMetadata = ft.UserMetadata && mask.UserMetadata
+	ft.ReadDirMetadata = ft.ReadDirMetadata && mask.ReadDirMetadata
+	ft.WriteDirMetadata = ft.WriteDirMetadata && mask.WriteDirMetadata
+	ft.WriteDirSetModTime = ft.WriteDirSetModTime && mask.WriteDirSetModTime
+	ft.UserDirMetadata = ft.UserDirMetadata && mask.UserDirMetadata
+	ft.DirModTimeUpdatesOnWrite = ft.DirModTimeUpdatesOnWrite && mask.DirModTimeUpdatesOnWrite
 	ft.CanHaveEmptyDirectories = ft.CanHaveEmptyDirectories && mask.CanHaveEmptyDirectories
 	ft.BucketBased = ft.BucketBased && mask.BucketBased
 	ft.BucketBasedRootOK = ft.BucketBasedRootOK && mask.BucketBasedRootOK
@@ -374,6 +396,9 @@ func (ft *Features) Mask(ctx context.Context, f Fs) *Features {
 	if mask.DirMove == nil {
 		ft.DirMove = nil
 	}
+	if mask.MkdirMetadata == nil {
+		ft.MkdirMetadata = nil
+	}
 	if mask.ChangeNotify == nil {
 		ft.ChangeNotify = nil
 	}
@@ -505,6 +530,18 @@ type DirMover interface {
 	DirMove(ctx context.Context, src Fs, srcRemote, dstRemote string) error
 }
 
+// MkdirMetadataer is an optional interface for Fs
+type MkdirMetadataer interface {
+	// MkdirMetadata makes the directory passed in as dir.
+	//
+	// It shouldn't return an error if it already exists.
+	//
+	// If the metadata is not nil it is set.
+	//
+	// It returns the directory that was created.
+	MkdirMetadata(ctx context.Context, dir string, metadata Metadata) (Directory, error)
+}
+
 // ChangeNotifier is an optional interface for Fs
 type ChangeNotifier interface {
 	// ChangeNotify calls the passed function with a path

fs/types.go

@@ -144,6 +144,16 @@ type Directory interface {
 	ID() string
 }
 
+// FullDirectory contains all the optional interfaces for Directory
+//
+// Use for checking making wrapping Directories implement everything
+type FullDirectory interface {
+	Directory
+	Metadataer
+	SetMetadataer
+	SetModTimer
+}
+
 // MimeTyper is an optional interface for Object
 type MimeTyper interface {
 	// MimeType returns the content type of the Object if
@@ -183,14 +193,32 @@ type GetTierer interface {
 	GetTier() string
 }
 
-// Metadataer is an optional interface for Object
+// Metadataer is an optional interface for DirEntry
 type Metadataer interface {
-	// Metadata returns metadata for an object
+	// Metadata returns metadata for an DirEntry
 	//
 	// It should return nil if there is no Metadata
 	Metadata(ctx context.Context) (Metadata, error)
 }
 
+// SetMetadataer is an optional interface for DirEntry
+type SetMetadataer interface {
+	// SetMetadata sets metadata for an DirEntry
+	//
+	// It should return fs.ErrorNotImplemented if it can't set metadata
+	SetMetadata(ctx context.Context, metadata Metadata) error
+}
+
+// SetModTimer is an optional interface for Directory.
+//
+// Object implements this as part of its requires set of interfaces.
+type SetModTimer interface {
+	// SetModTime sets the metadata on the DirEntry to set the modification date
+	//
+	// If there is any other metadata it does not overwrite it.
+	SetModTime(ctx context.Context, t time.Time) error
+}
+
 // FullObjectInfo contains all the read-only optional interfaces
 //
 // Use for checking making wrapping ObjectInfos implement everything
@@ -248,6 +276,29 @@ func ObjectOptionalInterfaces(o Object) (supported, unsupported []string) {
 	return supported, unsupported
 }
 
+// DirectoryOptionalInterfaces returns the names of supported and
+// unsupported optional interfaces for a Directory
+func DirectoryOptionalInterfaces(d Directory) (supported, unsupported []string) {
+	store := func(ok bool, name string) {
+		if ok {
+			supported = append(supported, name)
+		} else {
+			unsupported = append(unsupported, name)
+		}
+	}
+
+	_, ok := d.(Metadataer)
+	store(ok, "Metadata")
+
+	_, ok = d.(SetMetadataer)
+	store(ok, "SetMetadata")
+
+	_, ok = d.(SetModTimer)
+	store(ok, "SetModTime")
+
+	return supported, unsupported
+}
+
 // ListRCallback defines a callback function for ListR to use
 //
 // It is called for each tranche of entries read from the listing and