[PATCH 0/5] More builtin-fetch fixes

Yet another round of builtin-fetch fixes. This series fixes the latest breakage in `pu` for this topic along with an annoying warning when using the http transport.

The third patch in the series is a behavior change for git-fetch. The commit message discusses it in detail. Junio and I kicked this around on #git earlier this morning.

At this point myself and a few other experienced-with-Git coworkers are running this builtin-fetch "in production" for all daily tasks. We don't use *everything* that the tool supports as I did not know about this breakage in branch.$name.merge until tonight when Junio mentioned it, but for some of the really common cases we are quite happy with builtin-fetch. Especially its performance as we're seeing speedups of 25x or more on Cygwin/Windows.

I still believe there's work yet to be done on this topic as I'm quite sure the transfer.unpackLimit is not being honored. I meant to look at that tonight but wound up wasting all night and morning on the 3rd patch of this series. I will try to work on the unpackLimit issue Tuesday or Wednesday this week.