Naw, sarcasm totally works... ;)

I'd say it all depends -- there's that word again -- on what those 100 LOC are expressing. I suppose one could still copy/paste such a small amount of code, but I'd rather just check in some subset of vendored dependencies. Or maybe just pin the dependency to a commit hash (since we can't depend on version tags being immutable). Something actionable beyond peer pressure at any rate.

There are definitely 100-line chunks of code I wouldn't want to rewrite from scratch. They also tend not to be the sort of thing that needs a lot of updates, so a copy/paste job ought to do the job.

The big advantage with a dependency manager is that you don't have to find all of the dependency's dependencies, figure out the right build settings, etc. That's super helpful when it's huge, but it's not really doing anything for you when it's small.