Add a method to move down to the previous commit in branch

This wires "⌃↓" to do that

Author: tiennou

Classes/Controllers/PBGitHistoryController.h

@@ -62,6 +62,7 @@ NS_ASSUME_NONNULL_BEGIN
 // Find/Search methods
 - (IBAction)selectNext:(id)sender;
 - (IBAction)selectPrevious:(id)sender;
+- (IBAction)selectParentCommit:(id)sender;
 
 - (IBAction)copy:(id)sender;
 - (IBAction)copySHA:(id)sender;

Classes/Controllers/PBGitHistoryController.m

@@ -448,6 +448,21 @@ - (IBAction)selectPrevious:(id)sender
 	[searchController selectPreviousResult];
 }
 
+- (IBAction) selectParentCommit:(id)sender
+{
+	NSArray *selectedObjects = commitController.selectedObjects;
+	if (selectedObjects.count != 1) return;
+
+	PBGitCommit *selectedCommit = selectedObjects[0];
+
+	NSArray <GTOID *> *parents = selectedCommit.parents;
+	/* TODO: This is a merge commit. It would be nice to choose the parent with
+	 * the most commits, but for now we will use whatever commit is our first parent.
+	 */
+
+	[self selectCommit:parents[0]];
+}
+
 - (IBAction) copy:(id)sender
 {
 	[GitXCommitCopier putStringToPasteboard:[GitXCommitCopier toSHAAndHeadingString:commitController.selectedObjects]];

Classes/PBCommitList.m

@@ -43,7 +43,10 @@ - (void)keyDown:(NSEvent *)event
 	}
 	else if ([character rangeOfCharacterFromSet:[NSCharacterSet characterSetWithCharactersInString:@"jkcv"]].location == 0)
 		[webController sendKey: character];
-	else
+	else if (([character characterAtIndex:0] == NSDownArrowFunctionKey)
+			 && [event modifierFlags] & NSControlKeyMask) {
+		[controller selectParentCommit:self];
+	} else
 		[super keyDown: event];
 }