git vendor track creates .gitattributes at repo root instead of vendor directory

[jdc-pub]

When using git vendor track to add patterns to an existing vendor, it creates a new .gitattributes file at the repository root instead of updating the vendor-specific .gitattributes in the vendor directory.

This creates an untracked file at the root and leaves the vendor's .gitattributes directory untouched.

Expected: git vendor track should update or create the .gitattributes file in the vendor's target directory, consistent with git vendor add behavior.