Re: [PATCH 0/8] Avoid removing the current working directory, even if it becomes empty

"Elijah Newren via GitGitGadget" [off-list ref] writes:

Traditionally, if folks run git commands such as checkout or rebase from a
subdirectory, that git command could remove their current working directory
and result in subsequent git and non-git commands either getting confused or
printing messages that confuse the user (e.g. "fatal: Unable to read current
working directory: No such file or directory"). We already refuse to remove
directories that have untracked files within them[1], preferring to show an
error; with this series, we tweak that rule a bit to also refuse to remove
the current working directory even if it has no untracked files within it.

The goal is roughly that we do not allow rmdir() of a directory at
"prefix" in the working tree, or any parent directory of it, for
functions that uses RUN_SETUP?  By the time we attempt to rmdir(),
most likely we'd chdir()'ed up to the top of the working tree
ourselves, so we need to remember where the original cwd was when we
started, and protecting the original cwd would mean that we protect
the directory in which the process that spawned us, like the user's
interactive shell, is still sitting, which makes sense.