Fix block-wise autoindent when editing adjacent ranges (#19521)

This fixes problems where auto-indent wasn't working correctly for
assistant edits.

Release Notes:

- Fixed a bug where auto-indent didn't work correctly when pasting with
multiple cursors on adjacent lines

Co-authored-by: Marshall <marshall@zed.dev>

crates/language/src/buffer_tests.rs

@@ -1658,6 +1658,69 @@ fn test_autoindent_block_mode_without_original_indent_columns(cx: &mut AppContex
     });
 }
 
+#[gpui::test]
+fn test_autoindent_block_mode_multiple_adjacent_ranges(cx: &mut AppContext) {
+    init_settings(cx, |_| {});
+
+    cx.new_model(|cx| {
+        let (text, ranges_to_replace) = marked_text_ranges(
+            &"
+            mod numbers {
+                «fn one() {
+                    1
+                }
+            »
+                «fn two() {
+                    2
+                }
+            »
+                «fn three() {
+                    3
+                }
+            »}
+            "
+            .unindent(),
+            false,
+        );
+
+        let mut buffer = Buffer::local(text, cx).with_language(Arc::new(rust_lang()), cx);
+
+        buffer.edit(
+            [
+                (ranges_to_replace[0].clone(), "fn one() {\n    101\n}\n"),
+                (ranges_to_replace[1].clone(), "fn two() {\n    102\n}\n"),
+                (ranges_to_replace[2].clone(), "fn three() {\n    103\n}\n"),
+            ],
+            Some(AutoindentMode::Block {
+                original_indent_columns: vec![0, 0, 0],
+            }),
+            cx,
+        );
+
+        pretty_assertions::assert_eq!(
+            buffer.text(),
+            "
+            mod numbers {
+                fn one() {
+                    101
+                }
+
+                fn two() {
+                    102
+                }
+
+                fn three() {
+                    103
+                }
+            }
+            "
+            .unindent()
+        );
+
+        buffer
+    });
+}
+
 #[gpui::test]
 fn test_autoindent_language_without_indents_query(cx: &mut AppContext) {
     init_settings(cx, |_| {});