Allow dragging of files out of tree view

This uses the promisedfile protocol, which means that dragging to e.g.
FileMerge won't work.

PBGitTree.h

@@ -23,6 +23,7 @@
 
 + (PBGitTree*) rootForCommit: (id) commit;
 + (PBGitTree*) treeForTree: (PBGitTree*) tree andPath: (NSString*) path;
+- (void) saveToFolder: (NSString *) directory;
 
 - (NSString*) tmpFileNameForContents;
 

PBQLOutlineView.m

@@ -11,6 +11,20 @@
 
 @implementation PBQLOutlineView
 
+- initWithCoder: (NSCoder *) coder
+{
+	id a = [super initWithCoder:coder];
+	[a setDataSource: a];
+	[a registerForDraggedTypes: [NSArray arrayWithObject:NSFilesPromisePboardType]];
+	return a;
+}
+
+/* Needed to drag outside application */
+- (NSDragOperation)draggingSourceOperationMaskForLocal:(BOOL) local
+{
+	return NSDragOperationCopy;
+}
+
 - (void) keyDown: (NSEvent *) event
 {
 	if ([[event characters] isEqualToString:@" "]) {
@@ -20,4 +34,42 @@
 
 	[super keyDown:event];
 }
+
+- (BOOL)outlineView:(NSOutlineView *)outlineView writeItems:(NSArray *)items toPasteboard:(NSPasteboard *) pb
+{
+	NSMutableArray* fileNames = [NSMutableArray array];
+	for (id tree in items)
+		[fileNames addObject: [[[tree representedObject] path] pathExtension]];
+
+	[pb declareTypes:[NSArray arrayWithObject:NSFilesPromisePboardType] owner:self];
+    [pb setPropertyList:fileNames forType:NSFilesPromisePboardType];
+
+	return YES;
+}
+
+- (NSArray *)outlineView:(NSOutlineView *)outlineView namesOfPromisedFilesDroppedAtDestination:(NSURL *)dropDestination forDraggedItems:(NSArray *)items
+{
+	NSMutableArray* fileNames = [NSMutableArray array];
+	for (id obj in items) {
+		PBGitTree* tree = [obj representedObject];
+		[fileNames addObject: [tree path]];
+		[tree saveToFolder:[dropDestination path]];
+	}
+	return fileNames;
+}
+
+/* Implemented to satisfy datasourcee protocol */
+- (BOOL) outlineView: (NSOutlineView *)ov
+         isItemExpandable: (id)item { return NO; }
+
+- (int)  outlineView: (NSOutlineView *)ov
+         numberOfChildrenOfItem:(id)item { return 0; }
+
+- (id)   outlineView: (NSOutlineView *)ov
+         child:(int)index
+         ofItem:(id)item { return nil; }
+
+- (id)   outlineView: (NSOutlineView *)ov
+         objectValueForTableColumn:(NSTableColumn*)col
+         byItem:(id)item { return nil; }
 @end