fix(server): stop reporting a separate git dir as a branch's worktree

apps/server/src/vcs/GitVcsDriverCore.test.ts

@@ -825,6 +825,28 @@ it.effect("reads worktrees from git that rejects worktree list -z", () =>
   ).pipe(Effect.provide(layerServerConfig.pipe(Layer.provideMerge(NodeServices.layer)))),
 );
 
+it.effect("does not report a separate git dir as the worktree of its branch", () =>
+  Effect.scoped(
+    Effect.gen(function* () {
+      const driver = yield* GitVcsDriver.GitVcsDriver;
+      const cwd = yield* makeTmpDir();
+      const gitDir = yield* makeTmpDir();
+      yield* git(cwd, ["init", `--separate-git-dir=${gitDir}`]);
+      yield* git(cwd, ["config", "user.email", "test@test.com"]);
+      yield* git(cwd, ["config", "user.name", "Test"]);
+      yield* git(cwd, ["commit", "--allow-empty", "-m", "init"]);
+
+      const refs = yield* driver.listRefs({ cwd, refresh: true });
+      const worktreePath = refs.refs.find((ref) => ref.current)?.worktreePath;
+
+      assert.equal(
+        worktreePath && NodeFS.realpathSync.native(worktreePath),
+        NodeFS.realpathSync.native(cwd),
+      );
+    }),
+  ).pipe(Effect.provide(layerTest)),
+);
+
 it.effect("refreshes the current branch after an external checkout", () =>
   Effect.scoped(
     Effect.gen(function* () {

apps/server/src/vcs/GitVcsDriverCore.ts

@@ -3285,13 +3285,17 @@ export const makeGitVcsDriverCore = Effect.fn("makeGitVcsDriverCore")(function*
               [branchName, path.normalize(path.resolve(worktreePath))] as const,
           )
         : [];
+    // Without `core.worktree`, Git reports a separate git dir as the main checkout.
+    const normalizedGitCommonDir = path.normalize(path.resolve(gitCommonDir));
     const existingWorktreeEntries = yield* Effect.filter(
       parsedWorktreeEntries,
       ([, worktreePath]) =>
-        fileSystem.stat(worktreePath).pipe(
-          Effect.as(true),
-          Effect.orElseSucceed(() => false),
-        ),
+        worktreePath === normalizedGitCommonDir
+          ? Effect.succeed(false)
+          : fileSystem.stat(worktreePath).pipe(
+              Effect.as(true),
+              Effect.orElseSucceed(() => false),
+            ),
       { concurrency: 16 },
     );
     const worktreeMap = new Map(existingWorktreeEntries);
@@ -3482,6 +3486,9 @@ export const makeGitVcsDriverCore = Effect.fn("makeGitVcsDriverCore")(function*
         snapshot.localBranches.some((ref) => ref.worktreePath === repositoryPaths.worktreeRoot);
       const localBranches = snapshot.localBranches.map((ref) => ({
         ...ref,
+        worktreePath:
+          ref.worktreePath ??
+          (ref.name === repositoryPaths.currentBranch ? repositoryPaths.worktreeRoot : null),
         current: hasCurrentWorktreeBranch
           ? ref.worktreePath === repositoryPaths.worktreeRoot
           : ref.name === repositoryPaths.currentBranch,