On Mon, May 11, 2020 at 11:56:13AM +0000, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>
> As diff_tree_oid() computes a diff, it will terminate early if the
> total number of changed paths is strictly larger than max_changes.
> This includes the directories that changed, not just the file paths.
> However, only the file paths are reflected in the resulting diff
> queue's "nr" value.
>
> Use the "num_changes" from diffopt to check if the diff terminated
> early. This is incredibly important, as it can result in incorrect
> filters! For example, the first commit in the Linux kernel repo
> reports only 471 changes, but since these are nested inside several
> directories they expand to 513 "real" changes, and in fact the
> total list of changes is not reported. Thus, the computed filter
> for this commit is incorrect.
>
> Demonstrate the subtle difference by using one fewer file change
> in the 'get bloom filter for commit with 513 changes' test. Before,
> this edited 513 files inside "bigDir" which hit this inequality.
> However, dropping the file count by one demonstrates how the
> previous inequality was incorrect but the new one is correct.
>
> Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
> ---
> bloom.c | 2 +-
> t/t0095-bloom.sh | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/bloom.c b/bloom.c
> index 196cda0a1bd..e2ede44126c 100644
> --- a/bloom.c
> +++ b/bloom.c
> @@ -215,7 +215,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r,
> diff_tree_oid(NULL, &c->object.oid, "", &diffopt);
> diffcore_std(&diffopt);
>
> - if (diff_queued_diff.nr <= max_changes) {
> + if (diffopt.num_changes <= max_changes) {
The field 'diffopt.num_changes' is marked with:
/* For internal use only. */
> struct hashmap pathmap;
> struct pathmap_hash_entry *e;
> struct hashmap_iter iter;
> diff --git a/t/t0095-bloom.sh b/t/t0095-bloom.sh
> index 6defeb544f1..48a90625596 100755
> --- a/t/t0095-bloom.sh
> +++ b/t/t0095-bloom.sh
> @@ -100,7 +100,7 @@ test_expect_success EXPENSIVE 'get bloom filter for commit with 513 changes' '
> rm actual &&
> rm expect &&
> mkdir bigDir &&
> - for i in $(test_seq 0 512)
> + for i in $(test_seq 0 511)
> do
> echo $i >bigDir/$i
> done &&
> --
> gitgitgadget
>
