Git: Fix filling commit selection combobox for log

Broken by commit cbb70513bf, which changed the
format for the normal log to override the highlighter.

We still need the hightlighter for the log with diff.

Therefore, a separation between highlighting
and parsing the log is needed to populate the
combobox for commit selection again.

Change-Id: I902ce548fc25875f2cd67b165283ff1236329afa
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/vcsbase/vcsbaseeditor.cpp

@@ -828,6 +828,12 @@ void VcsBaseEditorWidget::setFileLogAnnotateEnabled(bool e)
     d->m_fileLogAnnotateEnabled = e;
 }
 
+void VcsBaseEditorWidget::setHighlightingEnabled(bool e)
+{
+    auto dh = static_cast<DiffAndLogHighlighter *>(textDocument()->syntaxHighlighter());
+    dh->setEnabled(e);
+}
+
 QString VcsBaseEditorWidget::workingDirectory() const
 {
     return d->m_workingDirectory;