Utils: Add a QString-based write to QtcProcess

Centralize some boiler plate and warn about best-guessed cases.

Keep the QByteArray based access as writeRaw()

Fixes: QTCREATORBUG-27445
Change-Id: I948d80fba78b36cf85cc73664175ab05eb7707d4
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/git/mergetool.cpp

@@ -176,7 +176,6 @@ void MergeTool::chooseAction()
     }
 
     msgBox.exec();
-    QByteArray ba;
     QVariant key;
     QAbstractButton *button = msgBox.clickedButton();
     if (button)
@@ -184,9 +183,8 @@ void MergeTool::chooseAction()
     // either the message box was closed without clicking anything, or abort was clicked
     if (!key.isValid())
         key = QVariant('a'); // abort
-    ba.append(key.toChar().toLatin1());
-    ba.append('\n');
-    write(ba);
+
+    write(QString(key.toChar()) + '\n');
 }
 
 void MergeTool::addButton(QMessageBox *msgBox, const QString &text, char key)
@@ -268,10 +266,10 @@ void MergeTool::done()
     deleteLater();
 }
 
-void MergeTool::write(const QByteArray &bytes)
+void MergeTool::write(const QString &str)
 {
-    m_process->write(bytes);
-    VcsOutputWindow::append(QString::fromLocal8Bit(bytes));
+    m_process->write(str);
+    VcsOutputWindow::append(str);
 }
 
 } // namespace Internal