Fix panic on paste when editing with auto-indent

Instead of accepting text as it's input by the user, we will read it
out of the edit operation after it gets sanitized by the buffer.

crates/language/src/tests.rs

@@ -22,6 +22,29 @@ fn init_logger() {
     }
 }
 
+#[gpui::test]
+fn test_line_endings(cx: &mut gpui::MutableAppContext) {
+    cx.add_model(|cx| {
+        let mut buffer =
+            Buffer::new(0, "one\r\ntwo\rthree", cx).with_language(Arc::new(rust_lang()), cx);
+        assert_eq!(buffer.text(), "one\ntwo\nthree");
+        assert_eq!(buffer.line_ending(), LineEnding::Windows);
+
+        buffer.check_invariants();
+        buffer.edit_with_autoindent(
+            [(buffer.len()..buffer.len(), "\r\nfour")],
+            IndentSize::spaces(2),
+            cx,
+        );
+        buffer.edit([(0..0, "zero\r\n")], cx);
+        assert_eq!(buffer.text(), "zero\none\ntwo\nthree\nfour");
+        assert_eq!(buffer.line_ending(), LineEnding::Windows);
+        buffer.check_invariants();
+
+        buffer
+    });
+}
+
 #[gpui::test]
 fn test_select_language() {
     let registry = LanguageRegistry::test();