fix: zed cannot recognize git repos managed by google repo tool

[can2049]

background

If a project is big, some times it will be split into many small git repo.
google repo is a tool to manage a group of git repos.

But, any small git repo manged by this tool, have a difference with normal git repo.
That is , the path .git in the root of the git repo, is not a normal directory, but a soft link to real git bare dir.

zed can not recognize the git-repo managed git repos

you can use the procedure to genreate this problem

# tested on linux
mkdir -p bad_git_repo_project
cd bad_git_repo_project
git init
echo "hello" > hi.txt
git add .
git commit -m "init commit"
echo "hello world" >> hi.txt

# modify the repo
mv .git ../.real_git_repo
ln -sf ../.real_git_repo .git

with vscode, after opening this project, git work well.
but for Zed, git not work(not git status, no git blame)

this is the PR link #21153