Drop git flow, or at least getopt.exe from MinGit

[dscho]

During a discussion about MinGit's MSYS contents today, I noticed that /usr/bin/getopt.exe from util-linux is included in MinGit. My follow-up investigation led to git-for-windows/build-extra@920c19b which explains that this is needed for git flow.

Seeing as there is a growing amount of evidence that not only is Git Flow over-engineered, but also that the original inventor is totally disinterested in maintaining it, even other volunteers who tried to maintain this over the years seem to have given up.

So let's drop git flow.

Or, if there is too much backlash against that, let's at least ensure that getopt.exe is no longer included in MinGit lest random users try to employ Hyrum's Law and force Git for Windows to bundle this totally unneeded executable forever.