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Introduce get_merge_bases_many()

This introduces a new function get_merge_bases_many() which is a natural extension of two commit merge base computation. It is given one commit (one) and a set of other commits (twos), and computes the merge base of one and a merge across other commits. This is mostly useful to figure out the common ancestor when iterating over heads during an octopus merge. When making an octopus between commits A, B, C and D, we first merge tree of A and B, and then try to merge C with it. If we were making pairwise merge, we would be recording the tree resulting from the merge between A and B as a commit, say M, and then the next round we will be computing the merge base between M and C. o---C...* / . o---B...M / . o---o---A But during an octopus merge, we actually do not create a commit M. In order to figure out that the common ancestor to use for this merge, instead of computing the merge base between C and M, we can call merge_bases_many() with one set to C and twos containing A and B. Signed-off-by: Junio C Hamano <gitster@pobox.com>

Junio C Hamano committed Jun 27, 2008 at 18:22 UTC 6a938648e1454842157b84408acbb6471ec6745f

1 file changed +38 -18

commit.c

+38 -18

@@ -533,26 +533,34 @@ static struct commit *interesting(struct commit_list *list)

533 return NULL;

534 }

535

536 -static struct commit_list *merge_bases(struct commit *one, struct commit *two)

536 +static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)

537 {

538 struct commit_list *list = NULL;

539 struct commit_list *result = NULL;

540 + int i;

541

541 - if (one == two)

542 - /* We do not mark this even with RESULT so we do not

543 - * have to clean it up.

544 - */

545 - return commit_list_insert(one, &result);

542 + for (i = 0; i < n; i++) {

543 + if (one == twos[i])

544 + /*

545 + * We do not mark this even with RESULT so we do not

546 + * have to clean it up.

547 + */

548 + return commit_list_insert(one, &result);

549 + }

550

551 if (parse_commit(one))

552 return NULL;

549 - if (parse_commit(two))

550 - return NULL;

553 + for (i = 0; i < n; i++) {

554 + if (parse_commit(twos[i]))

555 + return NULL;

556 + }

557

558 one->object.flags |= PARENT1;

553 - two->object.flags |= PARENT2;

559 insert_by_date(one, &list);

555 - insert_by_date(two, &list);

560 + for (i = 0; i < n; i++) {

561 + twos[i]->object.flags |= PARENT2;

562 + insert_by_date(twos[i], &list);

563 + }

564

565 while (interesting(list)) {

566 struct commit *commit;

@@ -627,21 +635,26 @@ struct commit_list *get_octopus_merge_bases(struct commit_list *in)

635 return ret;

636 }

637

630 -struct commit_list *get_merge_bases(struct commit *one,

631 - struct commit *two, int cleanup)

638 +struct commit_list *get_merge_bases_many(struct commit *one,

639 + int n,

640 + struct commit **twos,

641 + int cleanup)

642 {

643 struct commit_list *list;

644 struct commit **rslt;

645 struct commit_list *result;

646 int cnt, i, j;

647

638 - result = merge_bases(one, two);

639 - if (one == two)

640 - return result;

648 + result = merge_bases_many(one, n, twos);

649 + for (i = 0; i < n; i++) {

650 + if (one == twos[i])

651 + return result;

652 + }

653 if (!result || !result->next) {

654 if (cleanup) {

655 clear_commit_marks(one, all_flags);

644 - clear_commit_marks(two, all_flags);

656 + for (i = 0; i < n; i++)

657 + clear_commit_marks(twos[i], all_flags);

658 }

659 return result;

660 }

@@ -659,12 +672,13 @@ struct commit_list *get_merge_bases(struct commit *one,

672 free_commit_list(result);

673

674 clear_commit_marks(one, all_flags);

662 - clear_commit_marks(two, all_flags);

675 + for (i = 0; i < n; i++)

676 + clear_commit_marks(twos[i], all_flags);

677 for (i = 0; i < cnt - 1; i++) {

678 for (j = i+1; j < cnt; j++) {

679 if (!rslt[i] || !rslt[j])

680 continue;

667 - result = merge_bases(rslt[i], rslt[j]);

681 + result = merge_bases_many(rslt[i], 1, &rslt[j]);

682 clear_commit_marks(rslt[i], all_flags);

683 clear_commit_marks(rslt[j], all_flags);

684 for (list = result; list; list = list->next) {

@@ -686,6 +700,12 @@ struct commit_list *get_merge_bases(struct commit *one,

700 return result;

701 }

702

703 +struct commit_list *get_merge_bases(struct commit *one, struct commit *two,

704 + int cleanup)

705 +{

706 + return get_merge_bases_many(one, 1, &two, cleanup);

707 +}

708 +

709 int in_merge_bases(struct commit *commit, struct commit **reference, int num)

710 {

711 struct commit_list *bases, *b;