Re: [PATCH 0/4] Sparse checkout: fix bug with worktree of bare repo

On Mon, Dec 20, 2021 at 10:57 AM Derrick Stolee via GitGitGadget
[off-list ref] wrote:

This patch series includes a fix to the bug reported by Sean Allred [1] and
diagnosed by Eric Sunshine [2].

The root cause is that 'git sparse-checkout init' writes to the worktree
config without checking that core.bare might need to be set. This only
matters when the base repository is bare, since creating the config.worktree
file and enabling extensions.worktreeConfig will cause Git to treat the base
repo's core.bare=false as important for this worktree.

Thanks for jumping on this so quickly. Unfortunately, however, as
mentioned in [1] and [2], I think the approach implemented here of
setting `core.bare=false` in the worktree-specific config is
fundamentally flawed since it only addresses the problem for worktrees
in which `git sparse-checkout init` has been run, but leaves all other
worktrees potentially broken (both existing and new worktrees). As far
as I can see, the _only_ correct solution is for the new helper
function to enable `extensions.worktreeConfig` _and_ relocate
`core.bare` and `core.worktree` from .git/config to
.git/worktree.config, thus implementing the requirements documented in
git-worktree.txt.

I also raised a separate question in [2] about whether `git
sparse-checkout init` or the new helper function should be warning the
user that upgrading the repository format and setting
`extensions.worktreeConfig` might break third-party tools. However,
that question is tangential to the fix being addressed here and
doesn't need to be addressed by this series.

[1]: https://lore.kernel.org/git/CAPig+cQ6U_yFw-X2OWrizB1rbCvc4bNxuSzKFzmoLNnm0GH8Eg@mail.gmail.com/ (local)
[2]: https://lore.kernel.org/git/CAPig+cQPUe9REf+wgVNjyak_nk3V361h-48rTFgk6TGC7vJgOA@mail.gmail.com/ (local)