Index: release/scripts/startup/bl_ui/space_text.py
===================================================================
--- release/scripts/startup/bl_ui/space_text.py	(revision 45403)
+++ release/scripts/startup/bl_ui/space_text.py	(working copy)
@@ -273,6 +273,7 @@
         layout.operator("text.cut")
         layout.operator("text.copy")
         layout.operator("text.paste")
+        layout.operator("text.duplicate_line")
 
         layout.separator()
 
Index: source/blender/blenkernel/BKE_text.h
===================================================================
--- source/blender/blenkernel/BKE_text.h	(revision 45403)
+++ source/blender/blenkernel/BKE_text.h	(working copy)
@@ -96,6 +96,7 @@
 void 	txt_comment			(struct Text *text);
 void 	txt_indent			(struct Text *text);
 void	txt_uncomment		(struct Text *text);
+void	txt_duplicate_line	(struct Text *text);
 int	setcurr_tab_spaces	(struct Text *text, int space);
 
 void	txt_add_marker						(struct Text *text, struct TextLine *line, int start, int end, const unsigned char color[4], int group, int flags);
@@ -169,6 +170,8 @@
 #define UNDO_COMMENT    034
 #define UNDO_UNCOMMENT  035
 
+#define UNDO_DUPLICATE  040
+
 /* Marker flags */
 #define TMARK_TEMP		0x01	/* Remove on non-editing events, don't save */
 #define TMARK_EDITALL	0x02	/* Edit all markers of the same group as one */
Index: source/blender/blenkernel/intern/text.c
===================================================================
--- source/blender/blenkernel/intern/text.c	(revision 45403)
+++ source/blender/blenkernel/intern/text.c	(working copy)
@@ -2205,6 +2205,9 @@
 
 			text->undo_pos--;
 			break;
+		case UNDO_DUPLICATE:
+			txt_delete_line(text, text->curl->next);
+			break;
 		default:
 			//XXX error("Undo buffer error - resetting");
 			text->undo_pos= -1;
@@ -2402,6 +2405,9 @@
 				txt_uncomment(text);
 			}
 			break;
+		case UNDO_DUPLICATE:
+			txt_duplicate_line(text);
+			break;
 		default:
 			//XXX error("Undo buffer error - resetting");
 			text->undo_pos= -1;
@@ -2543,6 +2549,23 @@
 	txt_clean_text(text);
 }
 
+void txt_duplicate_line(Text *text)
+{
+	TextLine *textline;
+	
+	if (!text || !text->curl) return;
+	
+	if (text->curl == text->sell) {
+		textline = txt_new_line(text->curl->line);
+		BLI_insertlinkafter(&text->lines, text->curl, textline);
+		
+		txt_make_dirty(text);
+		txt_clean_text(text);
+		
+		if (!undoing) txt_undo_add_op(text, UNDO_DUPLICATE);
+	}
+}
+
 void txt_delete_char(Text *text) 
 {
 	unsigned int c='\n';
Index: source/blender/editors/space_text/space_text.c
===================================================================
--- source/blender/editors/space_text/space_text.c	(revision 45403)
+++ source/blender/editors/space_text/space_text.c	(working copy)
@@ -187,6 +187,7 @@
 	WM_operatortype_append(TEXT_OT_paste);
 	WM_operatortype_append(TEXT_OT_copy);
 	WM_operatortype_append(TEXT_OT_cut);
+	WM_operatortype_append(TEXT_OT_duplicate_line);
 
 	WM_operatortype_append(TEXT_OT_convert_whitespace);
 	WM_operatortype_append(TEXT_OT_uncomment);
@@ -297,6 +298,8 @@
 	WM_keymap_add_item(keymap, "TEXT_OT_cut", DELKEY, KM_PRESS, KM_SHIFT, 0);
 	WM_keymap_add_item(keymap, "TEXT_OT_copy", INSERTKEY, KM_PRESS, KM_CTRL, 0);
 	WM_keymap_add_item(keymap, "TEXT_OT_paste", INSERTKEY, KM_PRESS, KM_SHIFT, 0);
+	
+	WM_keymap_add_item(keymap, "TEXT_OT_duplicate_line", DKEY, KM_PRESS, KM_SHIFT | KM_CTRL, 0);
 
 	if (U.uiflag & USER_MMB_PASTE) { // XXX not dynamic
 		kmi = WM_keymap_add_item(keymap, "TEXT_OT_paste", MIDDLEMOUSE, KM_PRESS, 0, 0);
Index: source/blender/editors/space_text/text_intern.h
===================================================================
--- source/blender/editors/space_text/text_intern.h	(revision 45403)
+++ source/blender/editors/space_text/text_intern.h	(working copy)
@@ -118,6 +118,7 @@
 void TEXT_OT_paste(struct wmOperatorType *ot);
 void TEXT_OT_copy(struct wmOperatorType *ot);
 void TEXT_OT_cut(struct wmOperatorType *ot);
+void TEXT_OT_duplicate_line(struct wmOperatorType *ot);
 
 void TEXT_OT_convert_whitespace(struct wmOperatorType *ot);
 void TEXT_OT_uncomment(struct wmOperatorType *ot);
Index: source/blender/editors/space_text/text_ops.c
===================================================================
--- source/blender/editors/space_text/text_ops.c	(revision 45403)
+++ source/blender/editors/space_text/text_ops.c	(working copy)
@@ -826,6 +826,35 @@
 	RNA_def_boolean(ot->srna, "selection", 0, "Selection", "Paste text selected elsewhere rather than copied (X11 only)");
 }
 
+/**************** duplicate operator *******************/
+
+static int text_duplicate_line_exec(bContext *C, wmOperator *UNUSED(op))
+{
+	Text *text= CTX_data_edit_text(C);
+	
+	txt_duplicate_line(text);
+	
+	WM_event_add_notifier(C, NC_TEXT | NA_EDITED, text);
+
+	/* run the script while editing, evil but useful */
+	if (CTX_wm_space_text(C)->live_edit)
+		text_run_script(C, NULL);
+
+	return OPERATOR_FINISHED;
+}
+
+void TEXT_OT_duplicate_line(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Duplicate Line";
+	ot->idname = "TEXT_OT_duplicate_line";
+	ot->description = "Duplicate the current line";
+	
+	/* api callbacks */
+	ot->exec = text_duplicate_line_exec;
+	ot->poll = text_edit_poll;
+}
+
 /******************* copy operator *********************/
 
 static void txt_copy_clipboard(Text *text)