If you run ./libgit2_clar -s49 where that suite is part of the "network" category, it won't find it unless you also add -iall or -inetwork. If I know which suite I want to run explicitly, it shouldn't matter which category it's in. As the while suite belongs in one category, it's not like I can use it to run suite 49 except for the network tests.
So I think -s should imply -iall internally. I might take a stab later, for now I'm just complaining.
I think this is no longer relevant with clar v2. Categories were removed in favor of an easier way to include and exclude suites by name.