<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/142225>142225</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang-format] Main headers are ignored if priority is negative
        </td>
    </tr>

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

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

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

<pre>
    My work project coding style convention requires main header file to be last one. It means that all other headers must have negative priorities. But `IncludeCategoryManager::getIncludePriority` and `IncludeCategoryManager::getSortIncludePriority`  ignore such headers.

I tried 19.1.1 and `main` (49d48c32e04742ebd05cbbd7dd544b1217b6d9d0)

Configuration:

```
IncludeCategories:
 # C-Python header
  - Regex:           '^<Python\.h>$'
    Priority: -6
    CaseSensitive:   true
  # System headers
  - Regex: '^<.+\.h>$'
    Priority:        -5
    CaseSensitive:   true
  # STL headers
  - Regex:           '^<[a-z][a-z_]+>$'
    Priority:        -4
 CaseSensitive:   true
  # Boost headers
  - Regex: '^<boost/.+>$'
    Priority:        -3
    CaseSensitive:   true
  # Qt headers
  - Regex:           '^<Q.+>$'
    Priority:        -2
 CaseSensitive:   true
  # Local headers
  - Regex:           '^".+"$'
 Priority:        -1
    CaseSensitive:   true
```
</pre>
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