Does not support git worktrees

[harshg-db]

Repro steps:

1. cd ~/some_git_repo
2. Run git worktree add ~/test_worktree
3. Open ~/test_worktree and try to sync it to a workspace

Expected:
See a folder in wsfs

Actual:
Get an error Sync Error: unable to load repository specific gitconfig: open /Users/harsh.goyal/test_worktree/.git/config: not a directory

[danpicton]

This also happens the other direction too - if I run databricks workspace export-dir --debug --overwrite '/' ~/tmp/databricks-files/ to sync files locally for grepping, I encounter the same error:

Error: mkdir /Users/me/tmp/databricks-files/Repos/myuser/data-autoloader: not a directory

[pietern]

PR with support for Git worktrees is underway in #1831.