Merge #8054

8054: Item movers r=matklad a=ivan770

Closes #6823

https://user-images.githubusercontent.com/14003886/111331579-b4f43480-8679-11eb-9af0-e4dabacc4923.mp4

Implementation issues:
- [ ] Most of items are non-movable, since _movability_ of any item has to be determined manually. Common ones are movable though
- [x] Cursor should move with the item

Co-authored-by: ivan770 <leshenko.ivan770@gmail.com>

docs/dev/lsp-extensions.md

@@ -1,5 +1,5 @@
 <!---
-lsp_ext.rs hash: 4dfa8d7035f4aee7
+lsp_ext.rs hash: e8a7502bd2b2c2f5
 
 If you need to change the above hash to make the test pass, please check if you
 need to adjust this doc as well and ping this  issue:
@@ -595,3 +595,29 @@ interface TestInfo {
     runnable: Runnable;
 }
 ```
+
+## Hover Actions
+
+**Issue:** https://github.com/rust-analyzer/rust-analyzer/issues/6823
+
+This request is sent from client to server to move item under cursor or selection in some direction.
+
+**Method:** `experimental/moveItemUp`
+**Method:** `experimental/moveItemDown`
+
+**Request:** `MoveItemParams`
+
+**Response:** `TextDocumentEdit | null`
+
+```typescript
+export interface MoveItemParams {
+    textDocument: lc.TextDocumentIdentifier,
+    range: lc.Range,
+    direction: Direction
+}
+
+export const enum Direction {
+    Up = "Up",
+    Down = "Down"
+}
+```