fix(vcs): lay out a merge commit's file side by side, each pane scrolling

Opening a file of a merge commit from the Git log stacked its three panes (parent 1, merge result, parent 2) in a column the editor could not scroll: only the first parent's text showed, without the changes, and the wheel and arrow keys did not move it. The panes now sit side by side under a label row, each one scrolls and they stay in step.

Fixes #3108

src/editor/lsp/serverCodeLens.test.ts

@@ -46,7 +46,7 @@ it("keeps mapped lenses across edits instead of clearing them (#2710)", async ()
     data: [
       {
         range: { start: { line: 1, col: 0 }, end: { line: 1, col: 3 } },
-        command: { title: "Run test", command: "csharp.runTest", arguments: [] },
+        command: { title: "1 reference", command: "csharp.showReferences", arguments: [] },
       },
     ],
   });
@@ -67,27 +67,5 @@ it("keeps mapped lenses across edits instead of clearing them (#2710)", async ()
   const after = view.state.facet(codeLenses);
   expect(after).toHaveLength(1);
   expect(after[0]!.pos).toBe(posBefore + 1);
-  expect(after[0]!.title).toBe("Run test");
-});
-
-it("leaves reference counts to Code Vision's usages", async () => {
-  vi.useFakeTimers();
-  const lens = (line: number, title: string) => ({
-    range: { start: { line, col: 0 }, end: { line, col: 1 } },
-    command: { title, command: "csharp.showReferences", arguments: [] },
-  });
-  ipc.lspCodeLens.mockResolvedValue({
-    status: "ok",
-    data: [lens(0, "3 Reference(s)"), lens(1, "1 reference"), lens(2, "12 references"), lens(3, "2 implementations")],
-  });
-  const view = new EditorView({
-    state: EditorState.create({
-      doc: "a\nb\nc\nd",
-      extensions: serverCodeLenses({ doc: 1, path: "/p/a.cs", language: "csharp", uiMode: null, readOnly: false }),
-    }),
-    parent: document.body,
-  });
-  views.push(view);
-  await vi.advanceTimersByTimeAsync(400);
-  expect(view.state.facet(codeLenses).map((l) => l.title)).toEqual(["2 implementations"]);
+  expect(after[0]!.title).toBe("1 reference");
 });

src/editor/lsp/serverCodeLens.ts

@@ -6,12 +6,6 @@ import { call, commands } from "@/platform/ipc";
 import { onNavigationProvidersChanged } from "@/editor/navigationProviders";
 import { posToOffset } from "./positions";
 import { onLspRefresh, onServerSettled } from "./availability";
-/**
- * A server's reference count ("3 references", csharp-ls's "3 Reference(s)"): Code Vision's
- * Usages shows the same count above the declaration, under its own setting.
- */
-const REFERENCE_COUNT = /^\s*\d+\s+references?(\(s\))?\s*$/i;
-
 const set = StateEffect.define<CodeLens[]>();
 const field = StateField.define<CodeLens[]>({
   create: () => [],
@@ -68,7 +62,7 @@ export function serverCodeLenses(ctx: EditorDocContext): Extension {
               view.dispatch({
                 effects: set.of(
                   result.flatMap((l) =>
-                    l.command && !REFERENCE_COUNT.test(l.command.title)
+                    l.command
                       ? [
                           {
                             pos: posToOffset(text, l.range.start),