Going to SCM status has the groups expanded

Previously these would not initially be expanded but the expansion state remembered. Now that we regularly clear cache of expanded URLs, it’s more tedious regularly having to expand these two groups.

It also introduce new API for having data sources return what items should be initially expanded, which probably makes sense for some data sources.

Frameworks/OakFileBrowser/src/FSOutlineViewDelegate.mm

@@ -188,6 +188,8 @@ static NSSet* VisibleItems (NSOutlineView* outlineView, FSItem* root, NSMutableS
 
 	if(dataSource = aDataSource)
 	{
+		if(NSArray* expandedByDefault = [dataSource expandedURLs])
+			[expandedURLs addObjectsFromArray:expandedByDefault];
 		[outlineView setDataSource:dataSource];
 		[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(itemDidReload:) name:FSItemDidReloadNotification object:dataSource];
 		[self expandAndSelectChildren:dataSource.rootItem expandAll:NO];

Frameworks/OakFileBrowser/src/io/FSDataSource.h

@@ -11,6 +11,7 @@ extern NSString* const FSItemDidReloadNotification;
 @property (nonatomic, retain) FSItem* rootItem;
 - (BOOL)reloadItem:(FSItem*)anItem; // Returns YES if reload happens in the background. An FSItemDidReloadNotification is posted when reload has completed.
 - (BOOL)unloadItem:(FSItem*)anItem;
+- (NSArray*)expandedURLs;
 @end
 
 static NSUInteger const kFSDataSourceOptionGroupsFirst   = (1 << 0);

Frameworks/OakFileBrowser/src/io/FSDataSource.mm

@@ -60,6 +60,11 @@ FSDataSource* DataSourceForURL (NSURL* anURL, NSUInteger someOptions)
 	return NO;
 }
 
+- (NSArray*)expandedURLs
+{
+	return nil;
+}
+
 // =====================================
 // = NSOutlineView Data Source Methods =
 // =====================================

Frameworks/OakFileBrowser/src/io/FSSCMDataSource.mm

@@ -148,6 +148,11 @@ _Iter prune_path_children (_Iter it, _Iter last)
 	return self;
 }
 
+- (NSArray*)expandedURLs
+{
+	return @[ URLAppend(self.rootItem.url, @".unstaged/"), URLAppend(self.rootItem.url, @".untracked/") ];
+}
+
 - (void)dealloc
 {
 	if(scmInfo && scmCallback)