Run only against a project, not a solution

[JosXa]

We would like to start gradually rolling out ReGitLint, first to run it against some autogenerated code, then only later against the entire (large) solution.
From the documentation, I cannot see a way to run the tool with a .csproj file, only with -s <solution.sln>. It also appears that running it with the -p "./only-here" flag won't respect a relative path when run from the directory in which the project resides.

Is there a way to let ReGitLint only touch files of a specific directory or C# project?