Properly preserve selection associativity in selection-extending commands

FIX: Make sure selection-extending commands preserve the associativity of the selection head.

Issue codemirror/dev#1681

Author: marijnh

package.json

@@ -27,7 +27,7 @@
   "license": "MIT",
   "dependencies": {
     "@codemirror/language": "^6.0.0",
-    "@codemirror/state": "^6.4.0",
+    "@codemirror/state": "^6.6.0",
     "@codemirror/view": "^6.27.0",
     "@lezer/common": "^1.1.0"
   },

src/commands.ts

@@ -311,7 +311,7 @@ export const selectMatchingBracket: StateCommand = ({state, dispatch}) => toMatc
 function extendSel(target: CommandTarget, how: (range: SelectionRange) => SelectionRange): boolean {
   let selection = updateSel(target.state.selection, range => {
     let head = how(range)
-    return EditorSelection.range(range.anchor, head.head, head.goalColumn, head.bidiLevel || undefined)
+    return EditorSelection.range(range.anchor, head.head, head.goalColumn, head.bidiLevel || undefined, head.assoc)
   })
   if (selection.eq(target.state.selection)) return false
   target.dispatch(setSel(target.state, selection))