Highlight selected commit's backgrounds with painter->fillRect

Qt was adding additional highlighting that was distracting.  This commit
fixes that issue by manually drawing the highlighted background color
instead of relying on Qt to do that.
See
Murmele#699

Author: jensenr30

src/ui/CommitList.cpp

@@ -635,9 +635,6 @@ class CommitDelegate : public QStyledItemDelegate {
         Settings::instance()->value(Setting::Id::ShowCommitsId, true).toBool();
     LayoutConstants constants = layoutConstants(compact);
 
-    // Draw background.
-    QStyledItemDelegate::paint(painter, opt, index);
-
     bool active = (opt.state & QStyle::State_Active);
     bool selected = (opt.state & QStyle::State_Selected);
     auto group = active ? QPalette::Active : QPalette::Inactive;
@@ -646,10 +643,16 @@ class CommitDelegate : public QStyledItemDelegate {
     QPalette palette = Application::theme()->commitList();
     QColor text = palette.color(group, textRole);
     QColor bright = palette.color(group, brightRole);
+    QColor highlight = palette.color(group, QPalette::Highlight);
 
     painter->save();
     painter->setRenderHints(QPainter::Antialiasing);
 
+    // Draw background.
+    if (selected) {
+      painter->fillRect(opt.rect, highlight);
+    }
+
     // Draw busy indicator.
     if (opt.features & QStyleOptionViewItem::HasDecoration) {
       QRect rect = decorationRect(option, index);