Commit da3efdb1 authored by Jay Soffian's avatar Jay Soffian Committed by Junio C Hamano

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: default avatarJay Soffian <[email protected]>
Signed-off-by: default avatarJunio C Hamano <[email protected]>
parent 5e1c71fd
......@@ -9,6 +9,7 @@
#include "object.h"
#include "remote.h"
#include "transport.h"
#include "string-list.h"
static const char receive_pack_usage[] = "git receive-pack <git-dir>";
......@@ -129,6 +130,7 @@ static void write_head_info(void)
struct command {
struct command *next;
const char *error_string;
unsigned int skip_update;
unsigned char old_sha1[20];
unsigned char new_sha1[20];
char ref_name[FLEX_ARRAY]; /* more */
......@@ -486,6 +488,63 @@ static void run_update_post_hook(struct command *commands)
}
}
static void check_aliased_update(struct command *cmd, struct string_list *list)
{
struct string_list_item *item;
struct command *dst_cmd;
unsigned char sha1[20];
char cmd_oldh[41], cmd_newh[41], dst_oldh[41], dst_newh[41];
int flag;
const char *dst_name = resolve_ref(cmd->ref_name, sha1, 0, &flag);
if (!(flag & REF_ISSYMREF))
return;
if ((item = string_list_lookup(dst_name, list)) == NULL)
return;
cmd->skip_update = 1;
dst_cmd = (struct command *) item->util;
if (!hashcmp(cmd->old_sha1, dst_cmd->old_sha1) &&
!hashcmp(cmd->new_sha1, dst_cmd->new_sha1))
return;
dst_cmd->skip_update = 1;
strcpy(cmd_oldh, find_unique_abbrev(cmd->old_sha1, DEFAULT_ABBREV));
strcat(cmd_newh, find_unique_abbrev(cmd->new_sha1, DEFAULT_ABBREV));
strcpy(dst_oldh, find_unique_abbrev(dst_cmd->old_sha1, DEFAULT_ABBREV));
strcat(dst_newh, find_unique_abbrev(dst_cmd->new_sha1, DEFAULT_ABBREV));
rp_error("refusing inconsistent update between symref '%s' (%s..%s) and"
" its target '%s' (%s..%s)",
cmd->ref_name, cmd_oldh, cmd_newh,
dst_cmd->ref_name, dst_oldh, dst_newh);
cmd->error_string = dst_cmd->error_string =
"inconsistent aliased update";
}
static void check_aliased_updates(struct command *commands)
{
struct command *cmd;
struct string_list ref_list = { NULL, 0, 0, 0 };
for (cmd = commands; cmd; cmd = cmd->next) {
struct string_list_item *item =
string_list_append(cmd->ref_name, &ref_list);
item->util = (void *)cmd;
}
sort_string_list(&ref_list);
for (cmd = commands; cmd; cmd = cmd->next)
check_aliased_update(cmd, &ref_list);
string_list_clear(&ref_list, 0);
}
static void execute_commands(struct command *commands, const char *unpacker_error)
{
struct command *cmd;
......@@ -503,10 +562,13 @@ static void execute_commands(struct command *commands, const char *unpacker_erro
return;
}
check_aliased_updates(commands);
head_name = resolve_ref("HEAD", sha1, 0, NULL);
for (cmd = commands; cmd; cmd = cmd->next)
cmd->error_string = update(cmd);
if (!cmd->skip_update)
cmd->error_string = update(cmd);
}
static struct command *read_head_info(void)
......@@ -541,12 +603,10 @@ static struct command *read_head_info(void)
if (strstr(refname + reflen + 1, "side-band-64k"))
use_sideband = LARGE_PACKET_MAX;
}
cmd = xmalloc(sizeof(struct command) + len - 80);
cmd = xcalloc(1, sizeof(struct command) + len - 80);
hashcpy(cmd->old_sha1, old_sha1);
hashcpy(cmd->new_sha1, new_sha1);
memcpy(cmd->ref_name, line + 82, len - 81);
cmd->error_string = NULL;
cmd->next = NULL;
*p = cmd;
p = &cmd->next;
}
......
......@@ -660,4 +660,53 @@ test_expect_success 'push with branches containing #' '
git checkout master
'
test_expect_success 'push into aliased refs (consistent)' '
mk_test heads/master &&
mk_child child1 &&
mk_child child2 &&
(
cd child1 &&
git branch foo &&
git symbolic-ref refs/heads/bar refs/heads/foo
git config receive.denyCurrentBranch false
) &&
(
cd child2 &&
>path2 &&
git add path2 &&
test_tick &&
git commit -a -m child2 &&
git branch foo &&
git branch bar &&
git push ../child1 foo bar
)
'
test_expect_success 'push into aliased refs (inconsistent)' '
mk_test heads/master &&
mk_child child1 &&
mk_child child2 &&
(
cd child1 &&
git branch foo &&
git symbolic-ref refs/heads/bar refs/heads/foo
git config receive.denyCurrentBranch false
) &&
(
cd child2 &&
>path2 &&
git add path2 &&
test_tick &&
git commit -a -m child2 &&
git branch foo &&
>path3 &&
git add path3 &&
test_tick &&
git commit -a -m child2 &&
git branch bar &&
test_must_fail git push ../child1 foo bar 2>stderr &&
grep "refusing inconsistent update" stderr
)
'
test_done
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