Re: [PATCH v2 5/6] Comment important codepaths regarding nuking untracked files/dirs

[Eric Sunshine <sunshine@sunshineco.com>]

On Fri, Sep 24, 2021 at 2:37 AM Elijah Newren via GitGitGadget
<gitgitgadget@gmail.com> wrote:
> In the last few commits we focused on code in unpack-trees.c that
> mistakenly removed untracked files or directories.  There may be more of
> those, but in this commit we change our focus: callers of toplevel
> commands that are expected to remove untracked files or directories.
>
> As noted previously, we have toplevel commands that are expected to
> delete untracked files such as 'read-tree --reset', 'reset --hard', and
> 'checkout --force'.  However, that does not mean that other highlevel
> commands that happen to call these other commands thought about or
> conveyed to users the possibility that untracked files could be removed.
> Audit the code for such callsites, and add comments near existing
> callsites to mention whether these are safe or not.
> [...]
> Signed-off-by: Elijah Newren <newren@gmail.com>
> ---
> diff --git a/builtin/worktree.c b/builtin/worktree.c
> @@ -356,6 +356,11 @@ static int add_worktree(const char *path, const char *refname,
> +               /*
> +                * NOTE: reset --hard is okay here, because 'worktree add'
> +                * refuses to work in an extant non-empty directory, so there
> +                * is no risk of deleting untracked files.
> +                */
>                 strvec_pushl(&cp.args, "reset", "--hard", "--no-recurse-submodules", NULL);

I understand that this comment helps you or some other person auditing
similar cases in the future, however, as a standalone comment for a
reader who isn't aware of the intention, it seems more confusing than
illuminating. It also detracts from the important purpose of `--hard`
here, which is that it is necessary in order to get `git reset` to
actually "checkout" the files into the empty directory, so use of
`--hard` is not an accident or carelessness.

These days, we'd probably just use:

    git restore --no-recurse-submodules .

instead (including the final `.`) to achieve the same, and that
wouldn't need any sort of cuationary comment like the one being added
by this patch. So, perhaps that's a better way to go, or maybe it's
outside the scope of this series...