[9fans] my git client, again

[9fans] my git client, again

[Dave MacFarlane]

I finally got a laptop that can connect to my network under Plan 9 so
I can work on my Go git client, and enough of it's done that I'm
primarily developing it under 9front/amd64 now. I've caught most of
the stupid things where I was taking for granted things that the
official git client had done as side-effects while I was bootstrapping
it under other OSes..  and I fixed some little things like it trying
to use $EDITOR instead of $editor under Plan 9.

I'm most of the way to having three-way merge done (the low-level
three-way read-tree is done, I just can't figure out any easy way to
handle git-merge-file(1) using ape/???, which means I can't handle
conflicts, which I need to do before adding it to the porcelain merge
command.) diff is also almost there (the basic low level
git-diff-files(1) and git-diff-index(1) work, including the "-p"
option to display a patch, I just need to write the porcelain diff
command so that you don't need to remember how to use them directly.)

I decided to rename the repo from "go-git" to "dgit", because typing
"go-" at the start of a command name is annoying, there's already a
more popular Go libgit2 implementation  named go-git, and I couldn't
think of a better name than just adding my initial to it, so if anyone
wants to try it or contribute, it now lives at
https://github.com/driusan/dgit instead.

- Dave