[5.x] Fix a bug where Saving entry would move it to the last place in the parent hierarchy

src/Http/Controllers/CP/Collections/EntriesController.php

@@ -244,9 +244,11 @@ public function update(Request $request, $collection, $entry)
                         $parent = null;
                     }
 
-                    $tree
-                        ->move($entry->id(), $parent)
-                        ->save();
+                    if (! $tree->isAlreadyInParent($entry->id(), $parent)) {
+                        $tree
+                            ->move($entry->id(), $parent)
+                            ->save();
+                    }
                 });
 
                 $entry->remove('parent');

src/Revisions/Revisable.php

@@ -94,9 +94,11 @@ public function publishWorkingCopy($options = [])
                 $parent = null;
             }
 
-            $tree
-                ->move($this->id(), $parent)
-                ->save();
+            if ($tree->isAlreadyInParent($item->id(), $parent)) {
+                $tree
+                    ->move($this->id(), $parent)
+                    ->save();
+            }
         }
 
         $item

src/Structures/Page.php

@@ -284,6 +284,11 @@ public function setChildren(array $children): self
         return $this;
     }
 
+    public function getChildren(): array
+    {
+        return $this->children;
+    }
+
     public function setPageData(array $data): self
     {
         $this->data = $data;

src/Structures/Tree.php

@@ -394,4 +394,19 @@ public function getCurrentDirtyStateAttributes(): array
             'tree' => $this->tree,
         ];
     }
+
+    public function isAlreadyInParent($entryId, $parentId = null): bool
+    {
+        if ($parentId) {
+            $parentPage = $this->find($parentId);
+            if (! $parentPage) {
+                return false;
+            }
+            $childrenIds = Arr::pluck($parentPage->getChildren(), $this->idKey());
+        } else {
+            $childrenIds = collect($this->tree)->pluck($this->idKey())->all();
+        }
+
+        return in_array($entryId, $childrenIds);
+    }
 }