Re: [PATCH 8/9] update-index: integrate with sparse index

[Elijah Newren <newren@gmail.com>]

On Tue, Jan 4, 2022 at 9:37 AM Victoria Dye via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> From: Victoria Dye <vdye@github.com>
>
> Enable usage of the sparse index with `update-index`. Most variations of
> `update-index` work without explicitly expanding the index or making any
> other updates in or outside of `update-index.c`.
>
> The one usage requiring additional changes is `--cacheinfo`; if a file
> inside a sparse directory was specified, the index would not be expanded
> until after the cache tree is invalidated, leading to a mismatch between the
> index and cache tree. This scenario is handled by rearranging
> `add_index_entry_with_check`, allowing `index_name_stage_pos` to expand the
> index *before* attempting to invalidate the relevant cache tree path,
> avoiding cache tree/index corruption.
>
> Signed-off-by: Victoria Dye <vdye@github.com>
> ---
>  builtin/update-index.c                   |  3 +++
>  read-cache.c                             | 10 +++++++---
>  t/t1092-sparse-checkout-compatibility.sh | 12 ++++++++++++
>  3 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/update-index.c b/builtin/update-index.c
> index 187203e8bb5..605cc693bbd 100644
> --- a/builtin/update-index.c
> +++ b/builtin/update-index.c
> @@ -1077,6 +1077,9 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
>
>         git_config(git_default_config, NULL);
>
> +       prepare_repo_settings(r);
> +       the_repository->settings.command_requires_full_index = 0;
> +
>         /* we will diagnose later if it turns out that we need to update it */
>         newfd = hold_locked_index(&lock_file, 0);
>         if (newfd < 0)
> diff --git a/read-cache.c b/read-cache.c
> index cbe73f14e5e..b4600e954b6 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -1339,9 +1339,6 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
>         int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
>         int new_only = option & ADD_CACHE_NEW_ONLY;
>
> -       if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
> -               cache_tree_invalidate_path(istate, ce->name);
> -
>         /*
>          * If this entry's path sorts after the last entry in the index,
>          * we can avoid searching for it.
> @@ -1352,6 +1349,13 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
>         else
>                 pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce), EXPAND_SPARSE);
>
> +       /*
> +        * Cache tree path should be invalidated only after index_name_stage_pos,
> +        * in case it expands a sparse index.
> +        */
> +       if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
> +               cache_tree_invalidate_path(istate, ce->name);
> +
>         /* existing match? Just replace it. */
>         if (pos >= 0) {
>                 if (!new_only)
> diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
> index 6804ab23a27..bc0741c970d 100755
> --- a/t/t1092-sparse-checkout-compatibility.sh
> +++ b/t/t1092-sparse-checkout-compatibility.sh
> @@ -1216,6 +1216,18 @@ test_expect_success 'sparse index is not expanded: blame' '
>         done
>  '
>
> +test_expect_success 'sparse index is not expanded: update-index' '
> +       init_repos &&
> +
> +       echo "test" >sparse-index/README.md &&
> +       echo "test2" >sparse-index/a &&
> +       rm -f sparse-index/deep/a &&
> +
> +       ensure_not_expanded update-index --add README.md &&
> +       ensure_not_expanded update-index a &&
> +       ensure_not_expanded update-index --remove deep/a
> +'

The commit message said this change was about --cacheinfo, but this
test doesn't use that option.  I'm confused; was this a bad patch
splitting by chance?

> +
>  # NEEDSWORK: a sparse-checkout behaves differently from a full checkout
>  # in this scenario, but it shouldn't.
>  test_expect_success 'reset mixed and checkout orphan' '
> --
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