eeshow/gui/sheet.c (toggle_old_new): Tab toggles between diff_old and diff_new

eeshow/README

@@ -174,6 +174,7 @@ Delete or Backspace	go to the next higher sheet in hierarchy
 PgUp			go to the previous sheet in sequence
 PgDn			go to the next sheet in sequence
 Up or Down		invoke the revision history (WIP)
+Tab			toggle between old and new revision
 D			when comparing revisions, show difference (default)
 N			show newer sheet
 O			show older sheet

eeshow/TODO

@@ -47,7 +47,6 @@ GUI:
   to new_sheet and old_sheet.
 
 GUI/history
-- use Tab to rapidly toggle between old/new sheet
 - should have quick way to show diff of a single commit
 - in history, set font to non-bold if showing details
 - add scrolling to history, for hot-keys

eeshow/gui/sheet.c

@@ -177,6 +177,12 @@ static void show_diff_cb(void *user)
 }
 
 
+static void toggle_old_new(struct gui_ctx *ctx)
+{
+	set_diff_mode(ctx, ctx->diff_mode == diff_new ? diff_old : diff_new);
+}
+
+
 static void revision_overlays_diff(struct gui_ctx *ctx)
 {
 	struct gui_hist *new = ctx->new_hist;
@@ -491,6 +497,10 @@ static void sheet_key(void *user, int x, int y, int keyval)
 	case GDK_KEY_KP_Down:
 		show_history(ctx, sel_old);
 		break;
+	case GDK_KEY_Tab:
+	case GDK_KEY_KP_Tab:
+		toggle_old_new(ctx);
+		break;
 
 	case GDK_KEY_n:
 		ctx->diff_mode = diff_new;