A question for the masses

Here's the deal: Men's shirts, right, everything I read about them says to hem them long, between mid-hip and the upper thigh, and talks about keeping decent on midnight runs to the jakes and all that. Extant garments I've seen look longer than modern shirts, but not as long as a modern nightshirt, for example. Okay.

And then I see jerkins and/or doublets (the terms seem to be used somewhat interchangeably; I've decided that jerkins lack sleeves that doublets have, but that's just me.) worn with tights. Sometimes there's a pair of "pumpkin pants" but sometimes not. Often I just see the leggings poking from under the bases of the jerkin, and no trace of the shirt. I never see a shirt hanging below the jerkin (okay, once, but that wasn't really a jerkin, it was more of a leather vest cut very large and laced wrong and I think the label was "Ye Authenticke Robin Hood Costume" or something) and I've seen lots of pictures of nice smooth-tighted tushies, so I don't think Lord Harcheston of Marplehamshireford is just cramming his hem into his tights while exiting the backhouse -- and this leads to my question.

Fellas, what do you do with your shirttails?

Where's his shirttail gone? I dunno! HELP!