Outliner: Collection - Duplicate Hierarchy, and Duplicate Linked Hierarchy

As per the suggestion on T57064, this introduces two new options to duplicate collections.
We then have:
* Duplicate > Collection (New collection with linked content).
* Duplicate > Hierachy (Duplicate entire hierarchy and make all contents single user).
* Duplicate > Linked Hierarchy (Duplicate entire hierarchy keeping content linked with original).

Development TODO: `single_object_users` can/should use the new functions.

Reviewers: brecht, mont29

Subscribers: pablovazquez, billreynish, JulienKaspar

Differential Revision: https://developer.blender.org/D4394

9 files changed, 354 insertions, 221 deletions

diff --git a/release/scripts/startup/bl_ui/space_outliner.py b/release/scripts/startup/bl_ui/space_outliner.py
index 33c68d50d56..159a97e8625 100644
--- a/release/scripts/startup/bl_ui/space_outliner.py
+++ b/release/scripts/startup/bl_ui/space_outliner.py
@@ -157,6 +157,17 @@ class OUTLINER_MT_collection_view_layer(Menu):
             layout.operator("outliner.collection_holdout_clear")
 
 
+class OUTLINER_MT_collection_duplicate(Menu):
+    bl_label = "Duplicate"
+
+    def draw(self, context):
+        layout = self.layout
+
+        layout.operator("outliner.collection_duplicate", text="Collection")
+        layout.operator("outliner.collection_duplicate_hierarchy", text="Hierarchy")
+        layout.operator("outliner.collection_duplicate_linked_hierarchy", text="Linked Hierarchy")
+
+
 class OUTLINER_MT_collection_visibility(Menu):
     bl_label = "Visibility"
 
@@ -192,7 +203,7 @@ class OUTLINER_MT_collection(Menu):
         space = context.space_data
 
         layout.operator("outliner.collection_new", text="New").nested = True
-        layout.operator("outliner.collection_duplicate", text="Duplicate")
+        layout.menu("OUTLINER_MT_collection_duplicate")
 
         layout.separator()
 
@@ -345,6 +356,7 @@ classes = (
     OUTLINER_MT_editor_menus,
     OUTLINER_MT_edit_datablocks,
     OUTLINER_MT_collection,
+    OUTLINER_MT_collection_duplicate,
     OUTLINER_MT_collection_new,
     OUTLINER_MT_collection_visibility,
     OUTLINER_MT_collection_view_layer,
diff --git a/source/blender/blenkernel/BKE_collection.h b/source/blender/blenkernel/BKE_collection.h
index 2e4d2a7bf2c..5e6f87e7f97 100644
--- a/source/blender/blenkernel/BKE_collection.h
+++ b/source/blender/blenkernel/BKE_collection.h
@@ -54,11 +54,13 @@ void               BKE_collection_free(struct Collection *collection);
 bool               BKE_collection_delete(struct Main *bmain, struct Collection *collection, bool hierarchy);
 
 struct Collection *BKE_collection_copy(struct Main *bmain, struct Collection *parent, struct Collection *collection);
-struct Collection *BKE_collection_copy_master(struct Main *bmain, struct Collection *collection, const int flag);
 void               BKE_collection_copy_data(struct Main *bmain, struct Collection *collection_dst, const struct Collection *collection_src, const int flag);
-void               BKE_collection_copy_full(struct Main *bmain, struct Collection *collection);
 void               BKE_collection_make_local(struct Main *bmain, struct Collection *collection, const bool lib_local);
 
+struct Collection *BKE_collection_duplicate(struct Main *bmain, struct Collection *parent, struct Collection *collection, const bool do_hierarchy, const bool do_deep_copy);
+struct Collection *BKE_collection_copy_master(struct Main *bmain, struct Collection *collection, const int flag);
+void               BKE_collection_copy_full(struct Main *bmain, struct Collection *collection);
+
 /* Master Collection for Scene */
 
 struct Collection *BKE_collection_master(const struct Scene *scene);
diff --git a/source/blender/blenkernel/BKE_object.h b/source/blender/blenkernel/BKE_object.h
index 58d648b4aa4..32bc2f03b9e 100644
--- a/source/blender/blenkernel/BKE_object.h
+++ b/source/blender/blenkernel/BKE_object.h
@@ -126,6 +126,8 @@ void BKE_object_make_local_ex(struct Main *bmain, struct Object *ob, const bool
 bool BKE_object_is_libdata(const struct Object *ob);
 bool BKE_object_obdata_is_libdata(const struct Object *ob);
 
+struct Object *BKE_object_duplicate(struct Main *bmain, const struct Object *ob, const int dupflag);
+
 void BKE_object_obdata_size_init(struct Object *ob, const float scale);
 
 void BKE_object_scale_to_mat3(struct Object *ob, float mat[3][3]);
diff --git a/source/blender/blenkernel/intern/collection.c b/source/blender/blenkernel/intern/collection.c
index 37ee6fbeaae..ce7a5b141a4 100644
--- a/source/blender/blenkernel/intern/collection.c
+++ b/source/blender/blenkernel/intern/collection.c
@@ -209,17 +209,72 @@ void BKE_collection_copy_data(
 	}
 }
 
+static void collection_duplicate_recursive(Main *bmain, GHash *visited, Collection *collection, const int dupflag)
+{
+	const bool is_first_run = (visited == NULL);
+	if (is_first_run) {
+		visited = BLI_ghash_ptr_new(__func__);
+		BKE_main_id_tag_idcode(bmain, ID_GR, LIB_TAG_DOIT, false);
+	}
+
+	if (collection->id.tag & LIB_TAG_DOIT) {
+		return;
+	}
+	collection->id.tag |= LIB_TAG_DOIT;
+
+	ListBase collection_object_list = {NULL, NULL};
+	BLI_duplicatelist(&collection_object_list, &collection->gobject);
+	for (CollectionObject *cob = collection_object_list.first; cob; cob = cob->next) {
+		Object *ob_old = cob->ob;
+		Object *ob_new = NULL;
+		void **ob_key_p, **ob_value_p;
+
+		if (!BLI_ghash_ensure_p_ex(visited, ob_old, &ob_key_p, &ob_value_p)) {
+			ob_new = BKE_object_duplicate(bmain, ob_old, dupflag);
+			*ob_key_p = ob_old;
+			*ob_value_p = ob_new;
+		}
+		else {
+			ob_new = *ob_value_p;
+		}
+
+		collection_object_add(bmain, collection, ob_new, 0, true);
+		collection_object_remove(bmain, collection, ob_old, false);
+	}
+	BLI_freelistN(&collection_object_list);
+
+	ListBase collection_child_list = {NULL, NULL};
+	BLI_duplicatelist(&collection_child_list, &collection->children);
+	for (CollectionChild *child = collection_child_list.first; child; child = child->next) {
+		Collection *child_collection_old = child->collection;
+		Collection *child_collection_new = BKE_collection_copy(bmain, collection, child_collection_old);
+
+		collection_duplicate_recursive(bmain, visited, child_collection_new, dupflag);
+		collection_child_remove(collection, child_collection_old);
+	}
+	BLI_freelistN(&collection_child_list);
+
+	if (is_first_run) {
+		BLI_ghash_free(visited, NULL, NULL);
+	}
+}
+
 /**
  * Makes a shallow copy of a Collection
  *
- * Add a new collection in the same level as the old one, copy any nested collections
- * but link the objects to the new collection (as oppose to copy them).
+ * Add a new collection in the same level as the old one, link any nested collections
+ * and finally link the objects to the new collection (as oppose to copy them).
  */
 Collection *BKE_collection_copy(Main *bmain, Collection *parent, Collection *collection)
 {
+	return BKE_collection_duplicate(bmain, parent, collection, false, false);
+}
+
+Collection *BKE_collection_duplicate(Main *bmain, Collection *parent, Collection *collection, const bool do_hierarchy, const bool do_deep_copy)
+{
 	/* It's not allowed to copy the master collection. */
 	if (collection->flag & COLLECTION_IS_MASTER) {
-		BLI_assert("!Master collection can't be copied");
+		BLI_assert("!Master collection can't be duplicated");
 		return NULL;
 	}
 
@@ -241,6 +296,10 @@ Collection *BKE_collection_copy(Main *bmain, Collection *parent, Collection *col
 		}
 	}
 
+	if (do_hierarchy) {
+		collection_duplicate_recursive(bmain, NULL, collection_new, (do_deep_copy) ? U.dupflag : 0);
+	}
+
 	BKE_main_collection_sync(bmain);
 
 	return collection_new;
diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 3c57a5f7086..c4d80fdd5e2 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -1427,6 +1427,240 @@ Object *BKE_object_copy(Main *bmain, const Object *ob)
 	return ob_copy;
 }
 
+Object *BKE_object_duplicate(Main *bmain, const Object *ob, const int dupflag)
+{
+	Material ***matarar;
+	ID *id;
+	int a, didit;
+	Object *obn = BKE_object_copy(bmain, ob);
+
+	/* 0 == full linked. */
+	if (dupflag == 0) {
+		return obn;
+	}
+
+#define ID_NEW_REMAP_US(a)	if (      (a)->id.newid) { (a) = (void *)(a)->id.newid;       (a)->id.us++; }
+#define ID_NEW_REMAP_US2(a)	if (((ID *)a)->newid)    { (a) = ((ID  *)a)->newid;     ((ID *)a)->us++;    }
+
+	/* duplicates using userflags */
+	if (dupflag & USER_DUP_ACT) {
+		BKE_animdata_copy_id_action(bmain, &obn->id, true);
+	}
+
+	if (dupflag & USER_DUP_MAT) {
+		for (a = 0; a < obn->totcol; a++) {
+			id = (ID *)obn->mat[a];
+			if (id) {
+				ID_NEW_REMAP_US(obn->mat[a])
+				else {
+					obn->mat[a] = ID_NEW_SET(obn->mat[a], BKE_material_copy(bmain, obn->mat[a]));
+				}
+				id_us_min(id);
+
+				if (dupflag & USER_DUP_ACT) {
+					BKE_animdata_copy_id_action(bmain, &obn->mat[a]->id, true);
+				}
+			}
+		}
+	}
+	if (dupflag & USER_DUP_PSYS) {
+		ParticleSystem *psys;
+		for (psys = obn->particlesystem.first; psys; psys = psys->next) {
+			id = (ID *) psys->part;
+			if (id) {
+				ID_NEW_REMAP_US(psys->part)
+				else {
+					psys->part = ID_NEW_SET(psys->part, BKE_particlesettings_copy(bmain, psys->part));
+				}
+
+				if (dupflag & USER_DUP_ACT) {
+					BKE_animdata_copy_id_action(bmain, &psys->part->id, true);
+				}
+
+				id_us_min(id);
+			}
+		}
+	}
+
+	id = obn->data;
+	didit = 0;
+
+	switch (obn->type) {
+		case OB_MESH:
+			if (dupflag & USER_DUP_MESH) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_mesh_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_CURVE:
+			if (dupflag & USER_DUP_CURVE) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_curve_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_SURF:
+			if (dupflag & USER_DUP_SURF) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_curve_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_FONT:
+			if (dupflag & USER_DUP_FONT) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_curve_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_MBALL:
+			if (dupflag & USER_DUP_MBALL) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_mball_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_LAMP:
+			if (dupflag & USER_DUP_LAMP) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_light_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_ARMATURE:
+			DEG_id_tag_update(&obn->id, ID_RECALC_GEOMETRY);
+			if (obn->pose)
+				BKE_pose_tag_recalc(bmain, obn->pose);
+			if (dupflag & USER_DUP_ARM) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_armature_copy(bmain, obn->data));
+					BKE_pose_rebuild(bmain, obn, obn->data, true);
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_LATTICE:
+			if (dupflag != 0) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_lattice_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_CAMERA:
+			if (dupflag != 0) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_camera_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_LIGHTPROBE:
+			if (dupflag != 0) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_lightprobe_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_SPEAKER:
+			if (dupflag != 0) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_speaker_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+		case OB_GPENCIL:
+			if (dupflag != 0) {
+				ID_NEW_REMAP_US2(obn->data)
+				else {
+					obn->data = ID_NEW_SET(obn->data, BKE_gpencil_copy(bmain, obn->data));
+					didit = 1;
+				}
+				id_us_min(id);
+			}
+			break;
+	}
+
+	/* Check if obdata is copied. */
+	if (didit) {
+		Key *key = BKE_key_from_object(obn);
+
+		Key *oldkey = BKE_key_from_object(ob);
+		if (oldkey != NULL) {
+			ID_NEW_SET(oldkey, key);
+		}
+
+		if (dupflag & USER_DUP_ACT) {
+			BKE_animdata_copy_id_action(bmain, (ID *)obn->data, true);
+			if (key) {
+				BKE_animdata_copy_id_action(bmain, (ID *)key, true);
+			}
+		}
+
+		if (dupflag & USER_DUP_MAT) {
+			matarar = give_matarar(obn);
+			if (matarar) {
+				for (a = 0; a < obn->totcol; a++) {
+					id = (ID *)(*matarar)[a];
+					if (id) {
+						ID_NEW_REMAP_US((*matarar)[a])
+						else {
+							(*matarar)[a] = ID_NEW_SET((*matarar)[a], BKE_material_copy(bmain, (*matarar)[a]));
+						}
+						id_us_min(id);
+					}
+				}
+			}
+		}
+	}
+
+#undef ID_NEW_REMAP_US
+#undef ID_NEW_REMAP_US2
+
+	BKE_libblock_relink_to_newid(&obn->id);
+
+	/* DAG_relations_tag_update(bmain); */ /* caller must do */
+
+	if (ob->data != NULL) {
+		DEG_id_tag_update_ex(bmain, (ID *)obn->data, ID_RECALC_EDITORS);
+	}
+
+	/* BKE_main_id_clear_newpoins(bmain); */ /* Called must do. */
+
+	return obn;
+}
+
 void BKE_object_make_local_ex(Main *bmain, Object *ob, const bool lib_local, const bool clear_proxy)
 {
 	bool is_local = false, is_lib = false;
diff --git a/source/blender/editors/object/object_add.c b/source/blender/editors/object/object_add.c
index 425035d41cc..b69c88ecb7f 100644
--- a/source/blender/editors/object/object_add.c
+++ b/source/blender/editors/object/object_add.c
@@ -2208,20 +2208,14 @@ void OBJECT_OT_convert(wmOperatorType *ot)
 /* Does set ID->newid pointers. */
 static Base *object_add_duplicate_internal(Main *bmain, Scene *scene, ViewLayer *view_layer, Object *ob, int dupflag)
 {
-#define ID_NEW_REMAP_US(a)	if (      (a)->id.newid) { (a) = (void *)(a)->id.newid;       (a)->id.us++; }
-#define ID_NEW_REMAP_US2(a)	if (((ID *)a)->newid)    { (a) = ((ID  *)a)->newid;     ((ID *)a)->us++;    }
-
 	Base *base, *basen = NULL;
-	Material ***matarar;
 	Object *obn;
-	ID *id;
-	int a, didit;
 
 	if (ob->mode & OB_MODE_POSE) {
 		; /* nothing? */
 	}
 	else {
-		obn = ID_NEW_SET(ob, BKE_object_copy(bmain, ob));
+		obn = ID_NEW_SET(ob, BKE_object_duplicate(bmain, ob, dupflag));
 		DEG_id_tag_update(&obn->id, ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
 
 		base = BKE_view_layer_base_find(view_layer, ob);
@@ -2249,214 +2243,8 @@ static Base *object_add_duplicate_internal(Main *bmain, Scene *scene, ViewLayer
 					BKE_collection_object_add(bmain, collection, obn);
 			}
 		}
-
-		/* duplicates using userflags */
-		if (dupflag & USER_DUP_ACT) {
-			BKE_animdata_copy_id_action(bmain, &obn->id, true);
-		}
-
-		if (dupflag & USER_DUP_MAT) {
-			for (a = 0; a < obn->totcol; a++) {
-				id = (ID *)obn->mat[a];
-				if (id) {
-					ID_NEW_REMAP_US(obn->mat[a])
-					else {
-						obn->mat[a] = ID_NEW_SET(obn->mat[a], BKE_material_copy(bmain, obn->mat[a]));
-					}
-					id_us_min(id);
-
-					if (dupflag & USER_DUP_ACT) {
-						BKE_animdata_copy_id_action(bmain, &obn->mat[a]->id, true);
-					}
-				}
-			}
-		}
-		if (dupflag & USER_DUP_PSYS) {
-			ParticleSystem *psys;
-			for (psys = obn->particlesystem.first; psys; psys = psys->next) {
-				id = (ID *) psys->part;
-				if (id) {
-					ID_NEW_REMAP_US(psys->part)
-					else {
-						psys->part = ID_NEW_SET(psys->part, BKE_particlesettings_copy(bmain, psys->part));
-					}
-
-					if (dupflag & USER_DUP_ACT) {
-						BKE_animdata_copy_id_action(bmain, &psys->part->id, true);
-					}
-
-					id_us_min(id);
-				}
-			}
-		}
-
-		id = obn->data;
-		didit = 0;
-
-		switch (obn->type) {
-			case OB_MESH:
-				if (dupflag & USER_DUP_MESH) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_mesh_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_CURVE:
-				if (dupflag & USER_DUP_CURVE) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_curve_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_SURF:
-				if (dupflag & USER_DUP_SURF) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_curve_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_FONT:
-				if (dupflag & USER_DUP_FONT) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_curve_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_MBALL:
-				if (dupflag & USER_DUP_MBALL) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_mball_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_LAMP:
-				if (dupflag & USER_DUP_LAMP) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_light_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_ARMATURE:
-				DEG_id_tag_update(&obn->id, ID_RECALC_GEOMETRY);
-				if (obn->pose)
-					BKE_pose_tag_recalc(bmain, obn->pose);
-				if (dupflag & USER_DUP_ARM) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_armature_copy(bmain, obn->data));
-						BKE_pose_rebuild(bmain, obn, obn->data, true);
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_LATTICE:
-				if (dupflag != 0) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_lattice_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_CAMERA:
-				if (dupflag != 0) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_camera_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_LIGHTPROBE:
-				if (dupflag != 0) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_lightprobe_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_SPEAKER:
-				if (dupflag != 0) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_speaker_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-			case OB_GPENCIL:
-				if (dupflag != 0) {
-					ID_NEW_REMAP_US2(obn->data)
-					else {
-						obn->data = ID_NEW_SET(obn->data, BKE_gpencil_copy(bmain, obn->data));
-						didit = 1;
-					}
-					id_us_min(id);
-				}
-				break;
-		}
-
-		/* check if obdata is copied */
-		if (didit) {
-			Key *key = BKE_key_from_object(obn);
-
-			Key *oldkey = BKE_key_from_object(ob);
-			if (oldkey != NULL) {
-				ID_NEW_SET(oldkey, key);
-			}
-
-			if (dupflag & USER_DUP_ACT) {
-				BKE_animdata_copy_id_action(bmain, (ID *)obn->data, true);
-				if (key) {
-					BKE_animdata_copy_id_action(bmain, (ID *)key, true);
-				}
-			}
-
-			if (dupflag & USER_DUP_MAT) {
-				matarar = give_matarar(obn);
-				if (matarar) {
-					for (a = 0; a < obn->totcol; a++) {
-						id = (ID *)(*matarar)[a];
-						if (id) {
-							ID_NEW_REMAP_US((*matarar)[a])
-							else {
-								(*matarar)[a] = ID_NEW_SET((*matarar)[a], BKE_material_copy(bmain, (*matarar)[a]));
-							}
-							id_us_min(id);
-						}
-					}
-				}
-			}
-		}
 	}
 	return basen;
-
-#undef ID_NEW_REMAP_US
-#undef ID_NEW_REMAP_US2
 }
 
 /* single object duplicate, if dupflag==0, fully linked, else it uses the flags given */
diff --git a/source/blender/editors/space_outliner/outliner_collections.c b/source/blender/editors/space_outliner/outliner_collections.c
index 67126a3e155..61c02d18f8f 100644
--- a/source/blender/editors/space_outliner/outliner_collections.c
+++ b/source/blender/editors/space_outliner/outliner_collections.c
@@ -448,6 +448,8 @@ static int collection_duplicate_exec(bContext *C, wmOperator *op)
 	Main *bmain = CTX_data_main(C);
 	SpaceOutliner *soops = CTX_wm_space_outliner(C);
 	TreeElement *te = outliner_active_collection(C);
+	bool hierarchy = strstr(op->idname, "hierarchy") != NULL;
+	bool linked = strstr(op->idname, "linked") != NULL;
 
 	/* Can happen when calling from a key binding. */
 	if (te == NULL) {
@@ -467,7 +469,7 @@ static int collection_duplicate_exec(bContext *C, wmOperator *op)
 		case SO_SCENES:
 		case SO_VIEW_LAYER:
 		case SO_LIBRARIES:
-			BKE_collection_copy(bmain, parent, collection);
+			BKE_collection_duplicate(bmain, parent, collection, hierarchy, !linked);
 			break;
 	}
 
@@ -482,7 +484,37 @@ void OUTLINER_OT_collection_duplicate(wmOperatorType *ot)
 	/* identifiers */
 	ot->name = "Duplicate Collection";
 	ot->idname = "OUTLINER_OT_collection_duplicate";
-	ot->description = "Duplicate selected collections";
+	ot->description = "Make a new collection with linked content (collection and objects)";
+
+	/* api callbacks */
+	ot->exec = collection_duplicate_exec;
+	ot->poll = ED_outliner_collections_editor_poll;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
+void OUTLINER_OT_collection_duplicate_hierarchy(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Duplicate Collection Hierarchy";
+	ot->idname = "OUTLINER_OT_collection_duplicate_hierarchy";
+	ot->description = "Duplicate entire hierarchy and make all content single user";
+
+	/* api callbacks */
+	ot->exec = collection_duplicate_exec;
+	ot->poll = ED_outliner_collections_editor_poll;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+}
+
+void OUTLINER_OT_collection_duplicate_linked_hierarchy(wmOperatorType *ot)
+{
+	/* identifiers */
+	ot->name = "Duplicate Linked Collection Hierarchy";
+	ot->idname = "OUTLINER_OT_collection_duplicate_linked_hierarchy";
+	ot->description = "Duplicate entire hierarchy with linked object data";
 
 	/* api callbacks */
 	ot->exec = collection_duplicate_exec;
diff --git a/source/blender/editors/space_outliner/outliner_intern.h b/source/blender/editors/space_outliner/outliner_intern.h
index 81b06cab3a1..a1751e90660 100644
--- a/source/blender/editors/space_outliner/outliner_intern.h
+++ b/source/blender/editors/space_outliner/outliner_intern.h
@@ -316,6 +316,8 @@ struct Collection *outliner_collection_from_tree_element(const TreeElement *te);
 
 void OUTLINER_OT_collection_new(struct wmOperatorType *ot);
 void OUTLINER_OT_collection_duplicate(struct wmOperatorType *ot);
+void OUTLINER_OT_collection_duplicate_hierarchy(struct wmOperatorType *ot);
+void OUTLINER_OT_collection_duplicate_linked_hierarchy(struct wmOperatorType *ot);
 void OUTLINER_OT_collection_delete(struct wmOperatorType *ot);
 void OUTLINER_OT_collection_objects_select(struct wmOperatorType *ot);
 void OUTLINER_OT_collection_objects_deselect(struct wmOperatorType *ot);
diff --git a/source/blender/editors/space_outliner/outliner_ops.c b/source/blender/editors/space_outliner/outliner_ops.c
index 81001c0160f..404ad17ba4e 100644
--- a/source/blender/editors/space_outliner/outliner_ops.c
+++ b/source/blender/editors/space_outliner/outliner_ops.c
@@ -94,6 +94,8 @@ void outliner_operatortypes(void)
 	/* collections */
 	WM_operatortype_append(OUTLINER_OT_collection_new);
 	WM_operatortype_append(OUTLINER_OT_collection_duplicate);
+	WM_operatortype_append(OUTLINER_OT_collection_duplicate_hierarchy);
+	WM_operatortype_append(OUTLINER_OT_collection_duplicate_linked_hierarchy);
 	WM_operatortype_append(OUTLINER_OT_collection_delete);
 	WM_operatortype_append(OUTLINER_OT_collection_objects_select);
 	WM_operatortype_append(OUTLINER_OT_collection_objects_deselect);