env GIT_WORK_TREE ignored by git describe --dirty

From: Moocowmoo . <moocowmoo@masternode.me>
Date: Jan 26, 2019, 00:52 UTC
Message-ID: <CANMbfitE+5HLo1sMowr5erJGwzLVv3Z9sHKEgvOeso5OeWVrBg@mail.gmail.com>
In-Reply-To: <CANMbfiuUHxkw822AvA+y0cJ+ao=pcrza7w4fgMn7vVx8AZqCwQ@mail.gmail.com>

git describe --dirty shows dirty when cwd not repo work directory.

Confirmed by osse on freenode irc #git

  ubuntu@wrk:~/tmp$ pwd
  /home/ubuntu/tmp
  ubuntu@wrk:~/tmp$ git clone https://github.com/ipfs/go-ipfs.git
  ubuntu@wrk:~/tmp$ GIT_DIR=/home/ubuntu/tmp/go-ipfs/.git
GIT_WORK_TREE=/home/ubuntu/tmp/go-ipfs git describe --dirty
  v0.4.18-381-gca77ecc76-dirty

  ubuntu@wrk:~/tmp$ cd go-ipfs
  ubuntu@wrk:~/tmp/go-ipfs$ GIT_DIR=/home/ubuntu/tmp/go-ipfs/.git
GIT_WORK_TREE=/home/ubuntu/tmp/go-ipfs git describe --dirty
  v0.4.18-381-gca77ecc76

workaround:
use -C arg instead of GIT_WORK_TREE
  git -C /path/to/work/directory describe --dirty
  v0.4.18-381-gca77ecc76

I tried to find the issue, but git's code isn't easy to grok in a few minutes. Thanks to osse and gxt for their help!

moocowmoo