Implement hashing of files without adding it to the object db

Libgit2sharp does not seem to provide the equivalent functionality to git hash-object, even though libgit2 implements it. At first glance, it seems relatively simple to add, and I was planning on working on it and submitting a pull request. I was thinking that there would be a method on Repository that relies on
git_repository_hashfile and the usage would look like

using (var repo = new Repository("/repo"))
{
    string sha;
    sha = repo.HashFile("relative/path.txt");
    sha = repo.HashFile("relative/path.txt", applyFilters: false);
    sha = repo.HashFile("/repo/file.txt");
}

Any feedback is welcome.

Commencez par le point d’entrée Repository et examinez la fonctionnalité libgit2 git_repository_hashfile décrite dans l’issue. Définissez les surcharges HashFile demandées, y compris l’option applyFilters et les chemins relatifs au dépôt ou absolus, tout en préservant l’exigence de ne pas ajouter le fichier à la base de données d’objets.