So instead of:
id = has_commit_patch_id(commit, &ids);
We should use some sort of iterator, in order to call:
id->commit->object.flags |= cherry_flag;
for all commits which are related to this patch?
--
Arnaud Morin
On 12.01.21 - 10:11, Jeff King wrote:
> On Tue, Jan 12, 2021 at 09:17:37AM -0500, Jeff King wrote:
>
> > It looks like this was broken in v2.10.0, via dfb7a1b4d0 (patch-ids:
> > stop using a hand-rolled hashmap implementation, 2016-07-29).
> >
> > I think the issue is that it is allowing duplicate entries in the
> > hashmap. The algorithm is something like:
> >
> > - iterate over left-hand commits, inserting patch-id for each into
> > hashmap
> >
> > - iterate over right-hand commits, seeing if any are present in
> > hashmap. If so, we exclude the commit _and_ mark the patch-id as
> > "seen"
> >
> > - iterate again over left-hand commits, omitting any whose patch-ids
> > are marked as "seen"
> >
> > So if two commits on the left-hand side have the same patch-id, if we
> > insert two entries into the hashmap, then only one of them is going to
> > get its "seen" flag marked in the middle step.
>
> Yeah, that's definitely it. Here's what the fix would look like directly
> on top of dfb7a1b4d0:
>
> diff --git a/patch-ids.c b/patch-ids.c
> index db31fa647a..a8ed4f0872 100644
> --- a/patch-ids.c
> +++ b/patch-ids.c
> @@ -66,12 +66,24 @@ struct patch_id *add_commit_patch_id(struct commit *commit,
> struct patch_ids *ids)
> {
> struct patch_id *key = xcalloc(1, sizeof(*key));
> + struct patch_id *old;
>
> if (init_patch_id_entry(key, commit, ids)) {
> free(key);
> return NULL;
> }
>
> + /*
> + * Don't allow duplicates. Note that we can't use hashmap_put here; we
> + * must retain the _old_ struct, because some commit->util is pointing
> + * to it.
> + */
> + old = hashmap_get(&ids->patches, key, ids);
> + if (old) {
> + free(key);
> + return old;
> + }
> +
> hashmap_add(&ids->patches, key);
> return key;
> }
> diff --git a/t/t6007-rev-list-cherry-pick-file.sh b/t/t6007-rev-list-cherry-pick-file.sh
> index 28d4f6b259..0c5f1dcc54 100755
> --- a/t/t6007-rev-list-cherry-pick-file.sh
> +++ b/t/t6007-rev-list-cherry-pick-file.sh
> @@ -207,4 +207,16 @@ test_expect_success '--count --left-right' '
> test_cmp expect actual
> '
>
> +test_expect_success '--cherry-pick with duplicates on each side' '
> + git checkout -b dup-orig &&
> + test_commit dup-base &&
> + git revert dup-base &&
> + git cherry-pick dup-base &&
> + git checkout -b dup-side HEAD~3 &&
> + test_tick &&
> + git cherry-pick -3 dup-orig &&
> + git rev-list --cherry-pick dup-orig...dup-side >actual &&
> + test_must_be_empty actual
> +'
> +
> test_done
>
>
> Unfortunately we can't do the same thing now. The "seen" flag went away
> in 683f17ec44 (patch-ids: replace the seen indicator with a commit
> pointer, 2016-07-29), in favor of having each patch_id struct point to a
> "struct commit". We could revert that, or turn that pointer into a list,
> but it gets worse. Later, b3dfeebb92 (rebase: avoid computing
> unnecessary patch IDs, 2016-07-29) built on that by lazily computing the
> patch-ids. So each patch_id struct must point to exactly one commit!
>
> We'll have to either:
>
> - split them apart into two structs at the time of the lazy computation
>
> or
>
> - accept having duplicate patch_ids, but on lookup make sure we find
> _all_ matches, not just the first one.
>
> Hmm, that last one might not be too bad, since we have
> hashmap_get_next() (it does mean iterating over a chained bucket
> linearly, but that's already the worst-case for a hash lookup).
>
> -Peff
