Add key navigation between index and workdir files (#921)

* Add key navigation between index and workdir files
Navigate to index files controller when Down button pressed while on the
last file of the workdir list
Navigate to workdir files controller when Up button pressed while on the
first files of the index list

* Use NSEventModifierFlags for declared modifiers
Use more precise type for long flags

GitUpKit/Interface/GIConstants.h

@@ -13,6 +13,7 @@
 //  You should have received a copy of the GNU General Public License
 //  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+#import <AppKit/NSEvent.h>
 #import <Foundation/Foundation.h>
 
 typedef NS_ENUM(unsigned short, GIKeyCode) {
@@ -29,3 +30,5 @@ typedef NS_ENUM(unsigned short, GIKeyCode) {
   kGIKeyCode_Return = 0x24,
   kGIKeyCode_Delete = 0x33
 };
+
+static const NSEventModifierFlags kGIKeyModifiersAll = NSEventModifierFlagShift | NSEventModifierFlagControl | NSEventModifierFlagCommand | NSEventModifierFlagOption;

GitUpKit/Views/GIAdvancedCommitViewController.m

@@ -309,6 +309,7 @@ - (void)_diffFilesViewControllerDidPressDelete:(GIDiffFilesViewController*)contr
 }
 
 - (BOOL)diffFilesViewController:(GIDiffFilesViewController*)controller handleKeyDownEvent:(NSEvent*)event {
+  // Stage/Unstage files by Return/Delete
   if (!(event.modifierFlags & NSEventModifierFlagDeviceIndependentFlagsMask)) {
     if (event.keyCode == kGIKeyCode_Return) {
       [self _diffFilesViewControllerDidPressReturn:controller];
@@ -319,6 +320,27 @@ - (BOOL)diffFilesViewController:(GIDiffFilesViewController*)controller handleKey
     }
   }
 
+  // Navigate beteween stated and unstaged files list by up/down arrows
+  NSEventModifierFlags modifiers = event.modifierFlags & kGIKeyModifiersAll;
+  if (controller == _workdirFilesViewController && !modifiers && event.keyCode == kGIKeyCode_Down) {
+    bool onlyLastFileSelected = (controller.selectedDeltas.count == 1) && (controller.selectedDelta == controller.deltas.lastObject);
+    bool hasIndexFiles = _indexFilesViewController.deltas.count > 0;
+    if (onlyLastFileSelected && hasIndexFiles) {
+      // move focus to next controller
+      [[controller.view window] selectNextKeyView:_workdirFilesViewController.view];
+      return YES;
+    }
+  } else if (controller == _indexFilesViewController && !modifiers && event.keyCode == kGIKeyCode_Up) {
+    bool onlyFirstFileSelected = (controller.selectedDeltas.count == 1) && (controller.selectedDelta == controller.deltas.firstObject);
+    bool hasWorkdirFiles =_workdirFilesViewController.deltas.count > 0;
+    if (onlyFirstFileSelected && hasWorkdirFiles) {
+      // move focus to previous controller
+      [[controller.view window] selectPreviousKeyView:_workdirFilesViewController.view];
+      return YES;
+    }
+  }
+
+  // Perform contextual action on a file
   if (controller == _workdirFilesViewController) {
     return [self handleKeyDownEvent:event forSelectedDeltas:_workdirFilesViewController.selectedDeltas withConflicts:_indexConflicts allowOpen:YES];
   } else if (controller == _indexFilesViewController) {