<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/136659>136659</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            .clang-tidy not automatically found by clang-tidy 20.1.2
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang-tidy
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          kenchung285
      </td>
    </tr>
</table>

<pre>
    I have a project that originally used clang-tidy 19.1.7, and we've recently upgraded to version 20.1.2. After upgrading, I've noticed a change in behavior regarding `.clang-tidy` file discovery.

In 19.1.7, `clang-tidy` was able to discover and apply our self-defined `.clang-tidy` files without explicitly passing the `-config-file` option. However, in 20.1.2, `clang-tidy` no longer discovers the `.clang-tidy` file at the project root unless we explicitly pass `-config-file`.

Worse, if we do pass the `-config-file` flag (pointing to the one in the project root), `clang-tidy` seems to ignore the `.clang-tidy` file under folder B, even when checking files located in that folder.

Here is the relevant directory structure:
```
project-root/
├── README.md
├── .clang-tidy           # Full rule config
├── folder A/
│   ├── some source files
│   └── ...
├── folder B/
│   └── .clang-tidy      # Contains "Checks: '-*'" to disable checks in this folder
└── folder C/
    ├── other source files
    └── ...
```

Expected behavior:
* Without `-config-file`, `clang-tidy` should discover and respect both the project-root `.clang-tidy` and the one under `folder B`.

Actual behavior:
* Without `-config-file`, `.clang-tidy` is not discovered at all in 20.1.2.
* With `-config-file`, `.clang-tidy` in `folder B` is ignored.
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJyclc-O4jgQxp_GXEpExoFADjlkmEbTh73sZc7GriTeMXbkP2F4-5WTQNMsPd1ahJRIqa_8q89VNvdetQaxIptvZPN9wWPorKt-oRFdNC3bbRZHKy_VK3R8QODQO_sPigCh4wGsU60yXOsLRI8ShOamXQYlL7Aqs1W2JWwP3Eg4I2HbAcGhQBNSeN86LlFCsDCg88oaYDRbZSyDugno5ghl2pTjdZIbG5RACRxEx02LoAwcseODsg4cttwlAZCCZm8opKDQKI0glRd2QHfJCK0JrV_NHSUp6HvJmXvgR42J8Koca-F9ry9gowOPullKbJRB-cGiHs4qdDYGwN-9VkKl4vvkumkhdJhkS2FNo9plik862wdlTQY_7BkHdIlOXd15imosaGtadDdQf839zAcexq_XnXTWBohGo_dwxkfOJ4CzfT-t8zjCNUkn7RT_QVGN5i0QtuutMmEs3o6h1oy7-AhEWPm0VI948kmrWmMd_qnMaCQ6aKxOj28pGw5o4NyhAdGh-JUopj3SVvCAcgLhYRbNdf5Ah6CmwhxqHLgJIJVDEay7gA8uihAdkjxFk4LOf1rPBS2ngg7p6wsj5ZqU-_llR28v8PdL_f2vl-wkP4m7qxXefoTlcIhag4saYTL_k0SzNfU7tB1Lyf6g8vaE4G10Aif3PtCun6Fn2deYvn3M9DTvoyXJjb01gSvjgTC2T_vtSV4DYdslYTVhW8LYPNvjmI8t4acWUH4GuaN9tu5Mu59o4RPnbOjQPVoHX7PsrqsIrV9-9yhSw14Pv7n3WA0_5-PmvyP4fJ46G7V8f8A59Ck9HG3o7gdz7OMn05Y011Geho4U9LaRt_OiFiFy_X-QH9ZTPl0EN-Z0HwTgWr-dktld5q-nNQ_caaHpmJHZQla5LPOSL7BabdebnObbgi66apMXxWqz2u0amdMtZYwib3Z4LHZUbguUC1UxyjZ0zRgt8oLSrBSr9aaUDEsp2LZZkTXFE1c603o4Zda1C-V9xGqVF8WmXGh-RO3H-5mxO2LG0n3tqqRaHmPryZpq5YN_yxNU0FjdD0fyjcdgTzwoMd7bjY1GwvFyf3dPJi6i01UXQp_mJnU4O7QqdPGYCXsi7JCWmR_LuUMIO4zsnrDDjD9U7N8AAAD__4eTiqc">