diff --git a/CHANGELOG.md b/CHANGELOG.md
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+# Changelog
+
+## 0.1.0 - [2020-08-24]
+
+- first release
diff --git a/README.md b/README.md
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+# deno_is_git
+
+[![tag](https://img.shields.io/github/release/justjavac/deno_is_git)](https://github.com/justjavac/deno_is_git/releases)
+[![Build Status](https://github.com/justjavac/deno_is_git/workflows/ci/badge.svg?branch=master)](https://github.com/justjavac/deno_is_git/actions)
+[![license](https://img.shields.io/github/license/justjavac/deno_is_git)](https://github.com/justjavac/deno_is_git/blob/master/LICENSE)
+
+Whether the filepath is a **git repository**.
+
+## Usage
+
+```ts
+import { isGit, isGitSync } from "https://deno.land/x/is_git/mod.ts";
+
+await isGit(); // true or false of Deno.cwd()
+await isGit('any/git/repo'); // true or false
+
+isGitSync(); // true or false of Deno.cwd()
+isGitSync('any/git/repo'); // true or false
+```
+
+## Example
+
+```bash
+deno run --allow-read https://deno.land/x/is_git/example.ts
+```
+
+## License
+
+[deno_is_git](https://github.com/justjavac/deno_is_git) is released under the MIT License. See the bundled [LICENSE](./LICENSE) file for details.
diff --git a/example.ts b/example.ts
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+import { isGit } from "./mod.ts";
+
+console.log(`current directory is a git repository: ${await isGit()}`);
diff --git a/mod.ts b/mod.ts
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+++ b/mod.ts
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+import { join, isAbsolute } from "https://deno.land/std/path/mod.ts";
+import { exists, existsSync } from "https://deno.land/std/fs/exists.ts";
+
+/**
+ * Return `true` if the file apth is a git repository.
+ *
+ * Requires the `--allow-read` flag.
+ * 
+ * @param filepath default is `Deno.cwd()`, the current working directory.
+ */
+export function isGitSync(filepath = Deno.cwd()): boolean {
+  let current = isAbsolute(filepath) ? filepath : join(Deno.cwd(), filepath);
+  let parent = join(current, "..");
+
+  for (; parent! !== current; parent = join(current, "..")) {
+    if (existsSync(join(current, ".git"))) {
+      return true;
+    }
+    current = parent!;
+  }
+
+  return existsSync(join(current, ".git"));
+}
+
+/**
+ * Return `true` if the file apth is a git repository synchronously.
+ *
+ * Requires the `--allow-read` flag.
+ * 
+ * @param filepath default is `Deno.cwd()`, the current working directory.
+ */
+export async function isGit(filepath = Deno.cwd()): Promise<boolean> {
+  let current = isAbsolute(filepath) ? filepath : join(Deno.cwd(), filepath);
+  let parent = join(current, "..");
+
+  for (; parent! !== current; parent = join(current, "..")) {
+    if (await exists(join(current, ".git"))) {
+      return true;
+    }
+    current = parent!;
+  }
+
+  return exists(join(current, ".git"));
+}