*************
Adjustments needed in config_inc.php

// define level needed to be allowed to move attachments
$g_move_attachments_threshold = DEVELOPER;

*************************
Adjustements needed to customs_strings_inc.php

add the following lined just before the closing tag:
# 4 move attachments
$s_move_attachments ='Move attachments';
$s_move_attachments_tip ='Check to move attachments from parent to clone';


**************************************
Adjustments needed in bug_report_page.php and bug_report_advanced_page.php

Add the following section:
<!--CN-clone-attachments -->
<?php 
if ( file_bug_attachment_count( $f_master_bug_id ) > 0 ) {
	if ( access_has_project_level( config_get( 'move_attachments_threshold' ) ) ) { 
?>
<tr <?php echo helper_alternate_class() ?>>
	<td class="category">
		<?php echo lang_get( 'move_attachments' ) ?>
	</td>
	<td>
		<input tabindex="11" type="checkbox" name="move_attachments"  />  (<?php echo lang_get( 'move_attachments_tip' ) ?>)
	</td>
</tr>
<?php 
	}
}
?>
<!-- CN-clone-attachments -->

just before these statements:
<?php
	}
?>

<!-- Report Stay (report more bugs) -->

*****************************
Adjustment needed to bug_report_page.php

add the following lines :

// CN-CLONE-Attacchment
	$f_move_attachments		= gpc_get_bool( 'move_attachments' );
// CN-CLONE-Attacchment

just before:
	# if a profile was selected then let's use that information
	if ( 0 != $t_bug_data->profile_id ) {

add the following section :

// CN-CLONE-Attachment
	if ($f_move_attachments ) {
		// need to replace the bugid in the mantis_bug_file_table
		$t_bug_file_table	= config_get( 'mantis_bug_file_table' ); 
		$query= "update $t_bug_file_table set bug_id=";
		$query .= $t_bug_id;
		$query .= " where bug_id=";
		$query .= $f_master_bug_id ;
		$result = db_query( $query );
		if ($result){
			// need to add history on parent AND on clone
			history_log_event_special( $t_bug_id, FILE_ADDED, 'Moved files from parent to clone' );
			history_log_event_special( $f_master_bug_id, FILE_DELETED, 'Moved files to clone' );
			// create note on parent AND on clone
			$t_host = $_SERVER['HTTP_HOST'];
			$t_path = dirname( $_SERVER['PHP_SELF'] );
			if ( '/' == $t_path || '\\' == $t_path ) {
				$t_path = '';
			}
			$g_path	= 'http://' . $t_host . $t_path.'/';

			$private = false ;
			$bugnote_text = 'Files have been moved to issue :';
			$bugnote_text .= '<br>' ;
			$bugnote_text .= $g_path;
			$bugnote_text .= "/view.php?id=";
			$bugnote_text .= $t_bug_id ;
			bugnote_add( $f_master_bug_id, $bugnote_text, $private );

			$bugnote_text = 'Files have been moved from issue :';
			$bugnote_text .= '<br>' ;
			$bugnote_text .= $g_path;
			$bugnote_text .= "/view.php?id=";
			$bugnote_text .= $f_master_bug_id ;
			bugnote_add( $t_bug_id, $bugnote_text, $private );
		}
	}
// CN-CLONE-Attachment

just before :
	email_new_bug( $t_bug_id );