Fix signature in `git_repository_gc` The method returns an int with the amount of objects free'd
diff --git a/include/git2/repository.h b/include/git2/repository.h
index 5eff53b..317b367 100644
--- a/include/git2/repository.h
+++ b/include/git2/repository.h
@@ -167,7 +167,7 @@ GIT_EXTERN(void) git_repository_free(git_repository *repo);
*
* @param repo repository handle to collect. If NULL nothing occurs.
*/
-GIT_EXTERN(void) git_repository_gc(git_repository *repo);
+GIT_EXTERN(int) git_repository_gc(git_repository *repo);
/**
* Creates a new Git repository in the given folder.