[partition] Centralize setting-of-mountpoint

- map empty to the 0'th index
 - add new entries as needed

This avoids having selected index 0, but a different text.

src/modules/partition/gui/CreatePartitionDialog.cpp

@@ -328,7 +328,7 @@ CreatePartitionDialog::initFromPartitionToCreate( Partition* partition )
     m_ui->fsComboBox->setCurrentText( FileSystem::nameForType( fsType ) );
 
     // Mount point
-    m_ui->mountPointComboBox->setCurrentText( PartitionInfo::mountPoint( partition ) );
+    setSelectedMountPoint( m_ui->mountPointComboBox, PartitionInfo::mountPoint( partition ) );
 
     updateMountPointUi();
 }

src/modules/partition/gui/MountPoints.cpp

@@ -65,3 +65,24 @@ selectedMountPoint(QComboBox& combo)
         return QString();
     return combo.currentText();
 }
+
+void
+setSelectedMountPoint(QComboBox& combo, const QString& selected)
+{
+    cDebug() << "Setting mount point" << selected;
+    if ( selected.isEmpty() )
+        combo.setCurrentIndex( 0 );  // (no mount point)
+    else
+    {
+        for ( int i = 0; i < combo.count(); ++i )
+            if ( selected == combo.itemText( i ) )
+            {
+                cDebug() << " .. found at index" << i;
+                combo.setCurrentIndex( i );
+                return;
+            }
+        cDebug() << " .. new item";
+        combo.addItem( selected );
+        combo.setCurrentIndex( combo.count() - 1);
+    }
+}

src/modules/partition/gui/MountPoints.h

@@ -53,5 +53,7 @@ void standardMountPoints( QComboBox&, const QString& selected );
 QString selectedMountPoint( QComboBox& combo );
 static inline QString selectedMountPoint(QComboBox* combo) { return selectedMountPoint(*combo); }
 
+void setSelectedMountPoint( QComboBox& combo, const QString& selected );
+static inline void setSelectedMountPoint(QComboBox* combo, const QString& selected) { setSelectedMountPoint( *combo, selected); }
 
 #endif