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receive-pack: detect aliased updates which can occur with symrefs

When pushing to a remote repo the sending side filters out aliased updates (e.g., foo:baz bar:baz). However, it is not possible for the sender to know if two refs are aliased on the receiving side via symrefs. Here is one such scenario: $ git init origin $ (cd origin && touch file && git add file && git commit -a -m intial) $ git clone --bare origin origin.git $ rm -rf origin $ git clone origin.git client $ git clone --mirror client backup.git && $ (cd backup.git && git remote set-head origin --auto) $ (cd client && git remote add --mirror backup ../backup.git && echo change1 > file && git commit -a -m change1 && git push origin && git push backup ) The push to backup fails with: Counting objects: 5, done. Writing objects: 100% (3/3), 244 bytes, done. Total 3 (delta 0), reused 0 (delta 0) Unpacking objects: 100% (3/3), done. error: Ref refs/remotes/origin/master is at ef3... but expected 262... remote: error: failed to lock refs/remotes/origin/master To ../backup.git 262cd57..ef307ff master -> master 262cd57..ef307ff origin/HEAD -> origin/HEAD ! [remote rejected] origin/master -> origin/master (failed to lock) error: failed to push some refs to '../backup.git' The reason is that refs/remotes/origin/HEAD is a symref to refs/remotes/origin/master, but it is not possible for the sending side to unambiguously know this. This commit fixes the issue by having receive-pack ignore any update to a symref whose target is being identically updated. If a symref and its target are being updated inconsistently, then the update for both fails with an error message ("refusing inconsistent update...") to help diagnose the situation. Signed-off-by: Jay Soffian <jaysoffian@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jay Soffian committed Apr 19, 2010 at 18:19 UTC da3efdb17bef25dedc753131462ee784d822132e

2 files changed +113 -4

builtin-receive-pack.c

+64 -4

@@ -9,6 +9,7 @@

9 #include "object.h"

10 #include "remote.h"

11 #include "transport.h"

12 +#include "string-list.h"

14 static const char receive_pack_usage[] = "git receive-pack <git-dir>";

@@ -129,6 +130,7 @@ static void write_head_info(void)

130 struct command {

131 struct command *next;

132 const char *error_string;

133 + unsigned int skip_update;

134 unsigned char old_sha1[20];

135 unsigned char new_sha1[20];

136 char ref_name[FLEX_ARRAY]; /* more */

@@ -486,6 +488,63 @@ static void run_update_post_hook(struct command *commands)

488 }

489 }

490

491 +static void check_aliased_update(struct command *cmd, struct string_list *list)

492 +{

493 + struct string_list_item *item;

494 + struct command *dst_cmd;

495 + unsigned char sha1[20];

496 + char cmd_oldh[41], cmd_newh[41], dst_oldh[41], dst_newh[41];

497 + int flag;

498 +

499 + const char *dst_name = resolve_ref(cmd->ref_name, sha1, 0, &flag);

500 +

501 + if (!(flag & REF_ISSYMREF))

502 + return;

503 +

504 + if ((item = string_list_lookup(dst_name, list)) == NULL)

505 + return;

506 +

507 + cmd->skip_update = 1;

508 +

509 + dst_cmd = (struct command *) item->util;

510 +

511 + if (!hashcmp(cmd->old_sha1, dst_cmd->old_sha1) &&

512 + !hashcmp(cmd->new_sha1, dst_cmd->new_sha1))

513 + return;

514 +

515 + dst_cmd->skip_update = 1;

516 +

517 + strcpy(cmd_oldh, find_unique_abbrev(cmd->old_sha1, DEFAULT_ABBREV));

518 + strcat(cmd_newh, find_unique_abbrev(cmd->new_sha1, DEFAULT_ABBREV));

519 + strcpy(dst_oldh, find_unique_abbrev(dst_cmd->old_sha1, DEFAULT_ABBREV));

520 + strcat(dst_newh, find_unique_abbrev(dst_cmd->new_sha1, DEFAULT_ABBREV));

521 + rp_error("refusing inconsistent update between symref '%s' (%s..%s) and"

522 + " its target '%s' (%s..%s)",

523 + cmd->ref_name, cmd_oldh, cmd_newh,

524 + dst_cmd->ref_name, dst_oldh, dst_newh);

525 +

526 + cmd->error_string = dst_cmd->error_string =

527 + "inconsistent aliased update";

528 +}

529 +

530 +static void check_aliased_updates(struct command *commands)

531 +{

532 + struct command *cmd;

533 + struct string_list ref_list = { NULL, 0, 0, 0 };

534 +

535 + for (cmd = commands; cmd; cmd = cmd->next) {

536 + struct string_list_item *item =

537 + string_list_append(cmd->ref_name, &ref_list);

538 + item->util = (void *)cmd;

539 + }

540 + sort_string_list(&ref_list);

541 +

542 + for (cmd = commands; cmd; cmd = cmd->next)

543 + check_aliased_update(cmd, &ref_list);

544 +

545 + string_list_clear(&ref_list, 0);

546 +}

547 +

548 static void execute_commands(struct command *commands, const char *unpacker_error)

549 {

550 struct command *cmd;

@@ -503,10 +562,13 @@ static void execute_commands(struct command *commands, const char *unpacker_erro

562 return;

563 }

564

565 + check_aliased_updates(commands);

566 +

567 head_name = resolve_ref("HEAD", sha1, 0, NULL);

568

569 for (cmd = commands; cmd; cmd = cmd->next)

509 - cmd->error_string = update(cmd);

570 + if (!cmd->skip_update)

571 + cmd->error_string = update(cmd);

572 }

573

574 static struct command *read_head_info(void)

@@ -541,12 +603,10 @@ static struct command *read_head_info(void)

603 if (strstr(refname + reflen + 1, "side-band-64k"))

604 use_sideband = LARGE_PACKET_MAX;

605 }

544 - cmd = xmalloc(sizeof(struct command) + len - 80);

606 + cmd = xcalloc(1, sizeof(struct command) + len - 80);

607 hashcpy(cmd->old_sha1, old_sha1);

608 hashcpy(cmd->new_sha1, new_sha1);

609 memcpy(cmd->ref_name, line + 82, len - 81);

548 - cmd->error_string = NULL;

549 - cmd->next = NULL;

610 *p = cmd;

611 p = &cmd->next;

612 }

t/t5516-fetch-push.sh

+49

@@ -660,4 +660,53 @@ test_expect_success 'push with branches containing #' '

660 git checkout master

661 '

662

663 +test_expect_success 'push into aliased refs (consistent)' '

664 + mk_test heads/master &&

665 + mk_child child1 &&

666 + mk_child child2 &&

667 + (

668 + cd child1 &&

669 + git branch foo &&

670 + git symbolic-ref refs/heads/bar refs/heads/foo

671 + git config receive.denyCurrentBranch false

672 + ) &&

673 + (

674 + cd child2 &&

675 + >path2 &&

676 + git add path2 &&

677 + test_tick &&

678 + git commit -a -m child2 &&

679 + git branch foo &&

680 + git branch bar &&

681 + git push ../child1 foo bar

682 + )

683 +'

684 +

685 +test_expect_success 'push into aliased refs (inconsistent)' '

686 + mk_test heads/master &&

687 + mk_child child1 &&

688 + mk_child child2 &&

689 + (

690 + cd child1 &&

691 + git branch foo &&

692 + git symbolic-ref refs/heads/bar refs/heads/foo

693 + git config receive.denyCurrentBranch false

694 + ) &&

695 + (

696 + cd child2 &&

697 + >path2 &&

698 + git add path2 &&

699 + test_tick &&

700 + git commit -a -m child2 &&

701 + git branch foo &&

702 + >path3 &&

703 + git add path3 &&

704 + test_tick &&

705 + git commit -a -m child2 &&

706 + git branch bar &&

707 + test_must_fail git push ../child1 foo bar 2>stderr &&

708 + grep "refusing inconsistent update" stderr

709 + )

710 +'

711 +

712 test_done