diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 0f2ff188..250f9dcf 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -72,6 +72,11 @@ jobs:
       - run: git config --global core.autocrlf false
         if: runner.os == 'Windows'
 
+      - run: |
+          git config --global user.email "github-action@example.com"
+          git config --global user.name "GitHub Action"
+          git version
+
       - uses: actions/checkout@v4
 
       - uses: denoland/setup-deno@v1.1.4
diff --git a/deno.jsonc b/deno.jsonc
index fff1ecd8..8b698044 100644
--- a/deno.jsonc
+++ b/deno.jsonc
@@ -5,7 +5,7 @@
   ],
   "tasks": {
     "check": "deno check ./**/*.ts",
-    "test": "deno test -A --parallel --shuffle --doc",
+    "test": "deno test -A --shuffle --doc",
     "test:coverage": "deno task test --coverage=.coverage",
     "coverage": "deno coverage .coverage",
     "update": "deno run --allow-env --allow-read --allow-write --allow-run=git,deno --allow-net=jsr.io,registry.npmjs.org jsr:@molt/cli **/*.ts",
diff --git a/denops/gin/command/chaperon/util.ts b/denops/gin/command/chaperon/util.ts
index 14314df7..8653d136 100644
--- a/denops/gin/command/chaperon/util.ts
+++ b/denops/gin/command/chaperon/util.ts
@@ -1,5 +1,6 @@
 import * as fs from "jsr:@std/fs@^1.0.0";
 import * as path from "jsr:@std/path@^1.0.0";
+import { findGitdir } from "../../git/finder.ts";
 
 const beginMarker = `${"<".repeat(7)} `;
 const endMarker = `${">".repeat(7)} `;
@@ -29,8 +30,9 @@ export type AliasHead = typeof validAliasHeads[number];
 export async function getInProgressAliasHead(
   worktree: string,
 ): Promise<AliasHead | undefined> {
+  const gitdir = await findGitdir(worktree);
   for (const head of validAliasHeads) {
-    if (await fs.exists(path.join(worktree, ".git", head))) {
+    if (await fs.exists(path.join(gitdir, head))) {
       return head;
     }
   }
diff --git a/denops/gin/component/worktree.ts b/denops/gin/component/worktree.ts
index 10793955..b1e97d2e 100644
--- a/denops/gin/component/worktree.ts
+++ b/denops/gin/component/worktree.ts
@@ -2,7 +2,7 @@ import type { Denops } from "jsr:@denops/std@^7.0.0";
 import { Cache } from "jsr:@lambdalisue/ttl-cache@^1.0.0";
 import * as path from "jsr:@std/path@^1.0.0";
 import { findWorktreeFromDenops } from "../git/worktree.ts";
-import { find } from "../git/finder.ts";
+import { findWorktree } from "../git/finder.ts";
 
 type Data = string;
 
@@ -13,7 +13,7 @@ async function getData(
 ): Promise<Data> {
   return cache.get("data") ?? await (async () => {
     const worktree = await findWorktreeFromDenops(denops);
-    const result = await find(worktree);
+    const result = await findWorktree(worktree);
     cache.set("data", result);
     return result;
   })();
diff --git a/denops/gin/git/finder.ts b/denops/gin/git/finder.ts
index 7eec0ae9..821dcb58 100644
--- a/denops/gin/git/finder.ts
+++ b/denops/gin/git/finder.ts
@@ -4,17 +4,28 @@ import { execute } from "./process.ts";
 import { decodeUtf8 } from "../util/text.ts";
 
 const ttl = 30000; // seconds
-const cache = new Cache<string, string | Error>(ttl);
+const cacheWorktree = new Cache<string, string | Error>(ttl);
+const cacheGitdir = new Cache<string, string | Error>(ttl);
 
-export async function find(cwd: string): Promise<string> {
-  const result = cache.get(cwd) ?? await (async () => {
+/**
+ * Find a root path of a git working directory.
+ *
+ * @param cwd - A current working directory.
+ * @returns A root path of a git working directory.
+ */
+export async function findWorktree(cwd: string): Promise<string> {
+  const path = await Deno.realPath(cwd);
+  const result = cacheWorktree.get(path) ?? await (async () => {
     let result: string | Error;
     try {
-      result = await findInternal(cwd);
+      result = await revParse(path, [
+        "--show-toplevel",
+        "--show-superproject-working-tree",
+      ]);
     } catch (e) {
       result = e;
     }
-    cache.set(cwd, result);
+    cacheWorktree.set(path, result);
     return result;
   })();
   if (result instanceof Error) {
@@ -23,7 +34,31 @@ export async function find(cwd: string): Promise<string> {
   return result;
 }
 
-async function findInternal(cwd: string): Promise<string> {
+/**
+ * Find a .git directory of a git working directory.
+ *
+ * @param cwd - A current working directory.
+ * @returns A root path of a git working directory.
+ */
+export async function findGitdir(cwd: string): Promise<string> {
+  const path = await Deno.realPath(cwd);
+  const result = cacheGitdir.get(path) ?? await (async () => {
+    let result: string | Error;
+    try {
+      result = await revParse(path, ["--git-dir"]);
+    } catch (e) {
+      result = e;
+    }
+    cacheGitdir.set(path, result);
+    return result;
+  })();
+  if (result instanceof Error) {
+    throw result;
+  }
+  return result;
+}
+
+async function revParse(cwd: string, args: string[]): Promise<string> {
   const terms = cwd.split(SEPARATOR);
   if (terms.includes(".git")) {
     // `git rev-parse` does not work in a ".git" directory
@@ -31,16 +66,7 @@ async function findInternal(cwd: string): Promise<string> {
     const index = terms.indexOf(".git");
     cwd = terms.slice(0, index).join(SEPARATOR);
   }
-  const stdout = await execute(
-    [
-      "rev-parse",
-      "--show-toplevel",
-      "--show-superproject-working-tree",
-    ],
-    {
-      cwd,
-    },
-  );
+  const stdout = await execute(["rev-parse", ...args], { cwd });
   const output = decodeUtf8(stdout);
   return resolve(output.split(/\n/, 2)[0]);
 }
diff --git a/denops/gin/git/finder_test.ts b/denops/gin/git/finder_test.ts
index bfc54c00..90a543ff 100644
--- a/denops/gin/git/finder_test.ts
+++ b/denops/gin/git/finder_test.ts
@@ -1,34 +1,93 @@
 import { assertEquals, assertRejects } from "jsr:@std/assert@^1.0.0";
-import * as path from "jsr:@std/path@^1.0.0";
-import { find } from "./finder.ts";
+import { sandbox } from "jsr:@lambdalisue/sandbox@^2.0.0";
+import $ from "jsr:@david/dax@^0.42.0";
+import { join } from "jsr:@std/path@^1.0.0";
+import { findGitdir, findWorktree } from "./finder.ts";
 import { ExecuteError } from "./process.ts";
 
 Deno.test({
-  name: "find() returns a root path of a git working directory",
+  name: "findWorktree() returns a root path of a git working directory",
   fn: async () => {
-    const exp = path.resolve(
-      path.fromFileUrl(import.meta.url),
-      "../../../../",
+    await using sbox = await prepare();
+    Deno.chdir(join("a", "b", "c"));
+    assertEquals(await findWorktree("."), sbox.path);
+    // An internal cache will be used for the following call
+    assertEquals(await findWorktree("."), sbox.path);
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name:
+    "findWorktree() throws an error if the path is not in a git working directory",
+  fn: async () => {
+    await assertRejects(async () => {
+      await findWorktree("/");
+    }, ExecuteError);
+    // An internal cache will be used for the following call
+    await assertRejects(async () => {
+      await findWorktree("/");
+    }, ExecuteError);
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name: "findGitdir() returns a root path of a git working directory",
+  fn: async () => {
+    await using sbox = await prepare();
+    Deno.chdir(join("a", "b", "c"));
+    assertEquals(await findGitdir("."), join(sbox.path, ".git"));
+    // An internal cache will be used for the following call
+    assertEquals(await findGitdir("."), join(sbox.path, ".git"));
+  },
+  sanitizeResources: false,
+  sanitizeOps: false,
+});
+
+Deno.test({
+  name: "findGitdir() returns a worktree path of a git working directory",
+  fn: async () => {
+    await using sbox = await prepare();
+    await $`git worktree add -b test test main`;
+    Deno.chdir("test");
+    assertEquals(
+      await findGitdir("."),
+      join(sbox.path, ".git", "worktrees", "test"),
     );
-    assertEquals(await find("."), exp);
     // An internal cache will be used for the following call
-    assertEquals(await find("."), exp);
+    assertEquals(
+      await findGitdir("."),
+      join(sbox.path, ".git", "worktrees", "test"),
+    );
   },
   sanitizeResources: false,
   sanitizeOps: false,
 });
 
 Deno.test({
-  name: "find() throws an error if the path is not in a git working directory",
+  name:
+    "findGitdir() throws an error if the path is not in a git working directory",
   fn: async () => {
     await assertRejects(async () => {
-      await find("/");
+      await findGitdir("/");
     }, ExecuteError);
     // An internal cache will be used for the following call
     await assertRejects(async () => {
-      await find("/");
+      await findGitdir("/");
     }, ExecuteError);
   },
   sanitizeResources: false,
   sanitizeOps: false,
 });
+
+async function prepare(): ReturnType<typeof sandbox> {
+  const sbox = await sandbox();
+  await $`git init`;
+  await $`git commit --allow-empty -m 'Initial commit' --no-gpg-sign`;
+  await $`git switch -c main`;
+  await Deno.mkdir(join("a", "b", "c"), { recursive: true });
+  return sbox;
+}
diff --git a/denops/gin/git/worktree.ts b/denops/gin/git/worktree.ts
index 20afd04d..be68803c 100644
--- a/denops/gin/git/worktree.ts
+++ b/denops/gin/git/worktree.ts
@@ -5,7 +5,7 @@ import * as fn from "jsr:@denops/std@^7.0.0/function";
 import * as path from "jsr:@std/path@^1.0.0";
 import { GIN_BUFFER_PROTOCOLS } from "../global.ts";
 import { expand } from "../util/expand.ts";
-import { find } from "./finder.ts";
+import { findWorktree } from "./finder.ts";
 
 /**
  * Find a git worktree from a suspected directory
@@ -32,7 +32,7 @@ async function findWorktreeFromSuspect(
         console.debug(`Trying to find a git repository from '${c}'`);
       }
       try {
-        return await find(c);
+        return await findWorktree(c);
       } catch {
         // Fail silently
       }