Set keyboard focus reasonably when switching between views.

When you switch to the commit view, the commit message gets focus;
when you switch to the history view, the commit list gets focus.

PBGitCommitController.m

@@ -47,6 +47,10 @@
 	[webController closeView];
 	[super finalize];
 }
+- (NSResponder *)firstResponder;
+{
+	return commitMessageView;
+}
 
 - (IBAction)signOff:(id)sender
 {

PBGitHistoryController.m

@@ -179,6 +179,11 @@
 	[self refresh:nil];
 }
 
+- (NSResponder *)firstResponder;
+{
+	return commitList;
+}
+
 - (void) selectCommit: (NSString*) commit
 {
 	NSPredicate* selection = [NSPredicate predicateWithFormat:@"realSha == %@", commit];

PBGitWindowController.m

@@ -100,6 +100,7 @@
 	[self setNextResponder: viewController];
 	[self didChangeValueForKey:@"viewController"];	// this will trigger the NSTextField's value binding to change
 
+	[[self window] makeFirstResponder:[viewController firstResponder]];
 }
 
 - (void)awakeFromNib

PBViewController.h

@@ -23,4 +23,6 @@
 - (id)initWithRepository:(PBGitRepository *)theRepository superController:(PBGitWindowController *)controller;
 - (void) removeView;
 - (void) updateView;
+- (NSResponder *)firstResponder;
+
 @end

PBViewController.m

@@ -40,4 +40,9 @@
 - (void) updateView
 {
 }
+
+- (NSResponder *)firstResponder;
+{
+	return nil;
+}
 @end