Lage throws error when ran outside git repo

Describe the bug
Lage refuses to run if it's not in a git repo:

...> pnpm build

> monorepo@ build /home/paulius/code/other/lage-starter
> lage build

lage - Version 2.7.5 - 23 Workers
[11:15:15] - error     Error: Command failed with exit code 128: git ls-files -z
fatal: not a git repository (or any of the parent directories): .git
 ELIFECYCLE  Command failed with exit code 1.

Most users probably use lage in a git repo, but I wanted to try it out before creating one. Even when I initialized a git repo, it still wasn't satisfied as it couldn't find HEAD, so I also had to create a commit. I think that's a bit excessive, especially because lage doesn't seem to have any meaningful integration with git.

To Reproduce
Steps to reproduce the behavior:

1. Create an empty pnpm workspace in a local folder (not a git repo)
2. Add a package with a "build" script and a lage "build" pipeline
3. Try running lage build
4. See error above

Expected behavior
The build script should be called

Environment/Troubleshooting

  System:
    OS: Linux 5.15 openSUSE Tumbleweed 20230716
    CPU: (24) x64 Intel(R) Core(TM) i9-9920X CPU @ 3.50GHz
    Memory: 2.58 GB / 15.52 GB
    Container: Yes
    Shell: 5.2.15 - /bin/bash
  Binaries:
    Node: 18.16.1 - ~/.nvs/default/bin/node
    Yarn: 1.22.19 - ~/.local/share/pnpm/yarn
    npm: 9.5.1 - ~/.nvs/default/bin/npm
    pnpm: 8.6.7 - ~/.nvs/default/bin/pnpm
  Managers:
    pip3: 23.1.2 - /usr/bin/pip3
    RubyGems: 3.4.10 - /usr/bin/gem
  Utilities:
    Make: 4.4.1 - /usr/bin/make
    GCC: 13.1.1 - /usr/bin/gcc
    Git: 2.41.0 - /usr/bin/git
    Clang: 16.0.6 - /usr/bin/clang
    Mercurial: 6.4.4 - /usr/bin/hg
    Curl: 8.1.2 - /usr/bin/curl
  Virtualization:
    Docker: 24.0.4 - /usr/bin/docker
  IDEs:
    Nano: 7.2 - /usr/bin/nano
    VSCode: 1.80.1 - /home/paulius/.vscode-server/bin/74f6148eb9ea00507ec113ec51c489d6ffb4b771/bin/remote-cli/code
    Vim: 9.0 - /usr/bin/vim
  Languages:
    Bash: 5.2.15 - /usr/bin/bash
    Go: 1.20.5 - /usr/local/go/bin/go
    Perl: 5.36.1 - /usr/bin/perl
    Python3: 3.11.4 - /usr/bin/python3
    Ruby: 3.2.2 - /usr/bin/ruby
  Databases:
    PostgreSQL: 15.3 - /usr/bin/postgres

Start by searching the Lage source for the git ls-files -z invocation used by lage build; no file is named in the issue. Reproduce the empty pnpm workspace outside Git, then verify that lage build runs the package build script without requiring a repository or HEAD.