Merge branch 'js/maint-receive-pack-symref-alias'

* js/maint-receive-pack-symref-alias:
  t5516-fetch-push.sh: style cleanup
  receive-pack: detect aliased updates which can occur with symrefs
  receive-pack: switch global variable 'commands' to a parameter

Conflicts:
	t/t5516-fetch-push.sh

diff --cc builtin/receive-pack.c
index 0559fcc871894548050e99c8c258561a0dcad5c9,0000000000000000000000000000000000000000..bb34757d27f32fff8cb15a8f99d8295b5e38cb9e
mode 100644,000000..100644
--- 1/builtin/receive-pack.c
--- /dev/null
+++ b/builtin/receive-pack.c
@@@ -1,800 -1,0 +1,854 @@@
- static struct command *commands;
- 
 +#include "cache.h"
 +#include "pack.h"
 +#include "refs.h"
 +#include "pkt-line.h"
 +#include "sideband.h"
 +#include "run-command.h"
 +#include "exec_cmd.h"
 +#include "commit.h"
 +#include "object.h"
 +#include "remote.h"
 +#include "transport.h"
++#include "string-list.h"
 +
 +static const char receive_pack_usage[] = "git receive-pack <git-dir>";
 +
 +enum deny_action {
 +      DENY_UNCONFIGURED,
 +      DENY_IGNORE,
 +      DENY_WARN,
 +      DENY_REFUSE,
 +};
 +
 +static int deny_deletes;
 +static int deny_non_fast_forwards;
 +static enum deny_action deny_current_branch = DENY_UNCONFIGURED;
 +static enum deny_action deny_delete_current = DENY_UNCONFIGURED;
 +static int receive_fsck_objects;
 +static int receive_unpack_limit = -1;
 +static int transfer_unpack_limit = -1;
 +static int unpack_limit = 100;
 +static int report_status;
 +static int use_sideband;
 +static int prefer_ofs_delta = 1;
 +static int auto_update_server_info;
 +static int auto_gc = 1;
 +static const char *head_name;
 +static int sent_capabilities;
 +
 +static enum deny_action parse_deny_action(const char *var, const char *value)
 +{
 +      if (value) {
 +              if (!strcasecmp(value, "ignore"))
 +                      return DENY_IGNORE;
 +              if (!strcasecmp(value, "warn"))
 +                      return DENY_WARN;
 +              if (!strcasecmp(value, "refuse"))
 +                      return DENY_REFUSE;
 +      }
 +      if (git_config_bool(var, value))
 +              return DENY_REFUSE;
 +      return DENY_IGNORE;
 +}
 +
 +static int receive_pack_config(const char *var, const char *value, void *cb)
 +{
 +      if (strcmp(var, "receive.denydeletes") == 0) {
 +              deny_deletes = git_config_bool(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "receive.denynonfastforwards") == 0) {
 +              deny_non_fast_forwards = git_config_bool(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "receive.unpacklimit") == 0) {
 +              receive_unpack_limit = git_config_int(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "transfer.unpacklimit") == 0) {
 +              transfer_unpack_limit = git_config_int(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "receive.fsckobjects") == 0) {
 +              receive_fsck_objects = git_config_bool(var, value);
 +              return 0;
 +      }
 +
 +      if (!strcmp(var, "receive.denycurrentbranch")) {
 +              deny_current_branch = parse_deny_action(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "receive.denydeletecurrent") == 0) {
 +              deny_delete_current = parse_deny_action(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "repack.usedeltabaseoffset") == 0) {
 +              prefer_ofs_delta = git_config_bool(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "receive.updateserverinfo") == 0) {
 +              auto_update_server_info = git_config_bool(var, value);
 +              return 0;
 +      }
 +
 +      if (strcmp(var, "receive.autogc") == 0) {
 +              auto_gc = git_config_bool(var, value);
 +              return 0;
 +      }
 +
 +      return git_default_config(var, value, cb);
 +}
 +
 +static int show_ref(const char *path, const unsigned char *sha1, int flag, void *cb_data)
 +{
 +      if (sent_capabilities)
 +              packet_write(1, "%s %s\n", sha1_to_hex(sha1), path);
 +      else
 +              packet_write(1, "%s %s%c%s%s\n",
 +                           sha1_to_hex(sha1), path, 0,
 +                           " report-status delete-refs side-band-64k",
 +                           prefer_ofs_delta ? " ofs-delta" : "");
 +      sent_capabilities = 1;
 +      return 0;
 +}
 +
 +static void write_head_info(void)
 +{
 +      for_each_ref(show_ref, NULL);
 +      if (!sent_capabilities)
 +              show_ref("capabilities^{}", null_sha1, 0, NULL);
 +
 +}
 +
 +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 */
 +};
 +
- static int run_receive_hook(const char *hook_name)
 +static const char pre_receive_hook[] = "hooks/pre-receive";
 +static const char post_receive_hook[] = "hooks/post-receive";
 +
 +static void rp_error(const char *err, ...) __attribute__((format (printf, 1, 2)));
 +static void rp_warning(const char *err, ...) __attribute__((format (printf, 1, 2)));
 +
 +static void report_message(const char *prefix, const char *err, va_list params)
 +{
 +      int sz = strlen(prefix);
 +      char msg[4096];
 +
 +      strncpy(msg, prefix, sz);
 +      sz += vsnprintf(msg + sz, sizeof(msg) - sz, err, params);
 +      if (sz > (sizeof(msg) - 1))
 +              sz = sizeof(msg) - 1;
 +      msg[sz++] = '\n';
 +
 +      if (use_sideband)
 +              send_sideband(1, 2, msg, sz, use_sideband);
 +      else
 +              xwrite(2, msg, sz);
 +}
 +
 +static void rp_warning(const char *err, ...)
 +{
 +      va_list params;
 +      va_start(params, err);
 +      report_message("warning: ", err, params);
 +      va_end(params);
 +}
 +
 +static void rp_error(const char *err, ...)
 +{
 +      va_list params;
 +      va_start(params, err);
 +      report_message("error: ", err, params);
 +      va_end(params);
 +}
 +
 +static int copy_to_sideband(int in, int out, void *arg)
 +{
 +      char data[128];
 +      while (1) {
 +              ssize_t sz = xread(in, data, sizeof(data));
 +              if (sz <= 0)
 +                      break;
 +              send_sideband(1, 2, data, sz, use_sideband);
 +      }
 +      close(in);
 +      return 0;
 +}
 +
- static void run_update_post_hook(struct command *cmd)
++static int run_receive_hook(struct command *commands, const char *hook_name)
 +{
 +      static char buf[sizeof(commands->old_sha1) * 2 + PATH_MAX + 4];
 +      struct command *cmd;
 +      struct child_process proc;
 +      struct async muxer;
 +      const char *argv[2];
 +      int have_input = 0, code;
 +
 +      for (cmd = commands; !have_input && cmd; cmd = cmd->next) {
 +              if (!cmd->error_string)
 +                      have_input = 1;
 +      }
 +
 +      if (!have_input || access(hook_name, X_OK) < 0)
 +              return 0;
 +
 +      argv[0] = hook_name;
 +      argv[1] = NULL;
 +
 +      memset(&proc, 0, sizeof(proc));
 +      proc.argv = argv;
 +      proc.in = -1;
 +      proc.stdout_to_stderr = 1;
 +
 +      if (use_sideband) {
 +              memset(&muxer, 0, sizeof(muxer));
 +              muxer.proc = copy_to_sideband;
 +              muxer.in = -1;
 +              code = start_async(&muxer);
 +              if (code)
 +                      return code;
 +              proc.err = muxer.in;
 +      }
 +
 +      code = start_command(&proc);
 +      if (code) {
 +              if (use_sideband)
 +                      finish_async(&muxer);
 +              return code;
 +      }
 +
 +      for (cmd = commands; cmd; cmd = cmd->next) {
 +              if (!cmd->error_string) {
 +                      size_t n = snprintf(buf, sizeof(buf), "%s %s %s\n",
 +                              sha1_to_hex(cmd->old_sha1),
 +                              sha1_to_hex(cmd->new_sha1),
 +                              cmd->ref_name);
 +                      if (write_in_full(proc.in, buf, n) != n)
 +                              break;
 +              }
 +      }
 +      close(proc.in);
 +      if (use_sideband)
 +              finish_async(&muxer);
 +      return finish_command(&proc);
 +}
 +
 +static int run_update_hook(struct command *cmd)
 +{
 +      static const char update_hook[] = "hooks/update";
 +      const char *argv[5];
 +      struct child_process proc;
 +      int code;
 +
 +      if (access(update_hook, X_OK) < 0)
 +              return 0;
 +
 +      argv[0] = update_hook;
 +      argv[1] = cmd->ref_name;
 +      argv[2] = sha1_to_hex(cmd->old_sha1);
 +      argv[3] = sha1_to_hex(cmd->new_sha1);
 +      argv[4] = NULL;
 +
 +      memset(&proc, 0, sizeof(proc));
 +      proc.no_stdin = 1;
 +      proc.stdout_to_stderr = 1;
 +      proc.err = use_sideband ? -1 : 0;
 +      proc.argv = argv;
 +
 +      code = start_command(&proc);
 +      if (code)
 +              return code;
 +      if (use_sideband)
 +              copy_to_sideband(proc.err, -1, NULL);
 +      return finish_command(&proc);
 +}
 +
 +static int is_ref_checked_out(const char *ref)
 +{
 +      if (is_bare_repository())
 +              return 0;
 +
 +      if (!head_name)
 +              return 0;
 +      return !strcmp(head_name, ref);
 +}
 +
 +static char *refuse_unconfigured_deny_msg[] = {
 +      "By default, updating the current branch in a non-bare repository",
 +      "is denied, because it will make the index and work tree inconsistent",
 +      "with what you pushed, and will require 'git reset --hard' to match",
 +      "the work tree to HEAD.",
 +      "",
 +      "You can set 'receive.denyCurrentBranch' configuration variable to",
 +      "'ignore' or 'warn' in the remote repository to allow pushing into",
 +      "its current branch; however, this is not recommended unless you",
 +      "arranged to update its work tree to match what you pushed in some",
 +      "other way.",
 +      "",
 +      "To squelch this message and still keep the default behaviour, set",
 +      "'receive.denyCurrentBranch' configuration variable to 'refuse'."
 +};
 +
 +static void refuse_unconfigured_deny(void)
 +{
 +      int i;
 +      for (i = 0; i < ARRAY_SIZE(refuse_unconfigured_deny_msg); i++)
 +              rp_error("%s", refuse_unconfigured_deny_msg[i]);
 +}
 +
 +static char *refuse_unconfigured_deny_delete_current_msg[] = {
 +      "By default, deleting the current branch is denied, because the next",
 +      "'git clone' won't result in any file checked out, causing confusion.",
 +      "",
 +      "You can set 'receive.denyDeleteCurrent' configuration variable to",
 +      "'warn' or 'ignore' in the remote repository to allow deleting the",
 +      "current branch, with or without a warning message.",
 +      "",
 +      "To squelch this message, you can set it to 'refuse'."
 +};
 +
 +static void refuse_unconfigured_deny_delete_current(void)
 +{
 +      int i;
 +      for (i = 0;
 +           i < ARRAY_SIZE(refuse_unconfigured_deny_delete_current_msg);
 +           i++)
 +              rp_error("%s", refuse_unconfigured_deny_delete_current_msg[i]);
 +}
 +
 +static const char *update(struct command *cmd)
 +{
 +      const char *name = cmd->ref_name;
 +      unsigned char *old_sha1 = cmd->old_sha1;
 +      unsigned char *new_sha1 = cmd->new_sha1;
 +      struct ref_lock *lock;
 +
 +      /* only refs/... are allowed */
 +      if (prefixcmp(name, "refs/") || check_ref_format(name + 5)) {
 +              rp_error("refusing to create funny ref '%s' remotely", name);
 +              return "funny refname";
 +      }
 +
 +      if (is_ref_checked_out(name)) {
 +              switch (deny_current_branch) {
 +              case DENY_IGNORE:
 +                      break;
 +              case DENY_WARN:
 +                      rp_warning("updating the current branch");
 +                      break;
 +              case DENY_REFUSE:
 +              case DENY_UNCONFIGURED:
 +                      rp_error("refusing to update checked out branch: %s", name);
 +                      if (deny_current_branch == DENY_UNCONFIGURED)
 +                              refuse_unconfigured_deny();
 +                      return "branch is currently checked out";
 +              }
 +      }
 +
 +      if (!is_null_sha1(new_sha1) && !has_sha1_file(new_sha1)) {
 +              error("unpack should have generated %s, "
 +                    "but I can't find it!", sha1_to_hex(new_sha1));
 +              return "bad pack";
 +      }
 +
 +      if (!is_null_sha1(old_sha1) && is_null_sha1(new_sha1)) {
 +              if (deny_deletes && !prefixcmp(name, "refs/heads/")) {
 +                      rp_error("denying ref deletion for %s", name);
 +                      return "deletion prohibited";
 +              }
 +
 +              if (!strcmp(name, head_name)) {
 +                      switch (deny_delete_current) {
 +                      case DENY_IGNORE:
 +                              break;
 +                      case DENY_WARN:
 +                              rp_warning("deleting the current branch");
 +                              break;
 +                      case DENY_REFUSE:
 +                      case DENY_UNCONFIGURED:
 +                              if (deny_delete_current == DENY_UNCONFIGURED)
 +                                      refuse_unconfigured_deny_delete_current();
 +                              rp_error("refusing to delete the current branch: %s", name);
 +                              return "deletion of the current branch prohibited";
 +                      }
 +              }
 +      }
 +
 +      if (deny_non_fast_forwards && !is_null_sha1(new_sha1) &&
 +          !is_null_sha1(old_sha1) &&
 +          !prefixcmp(name, "refs/heads/")) {
 +              struct object *old_object, *new_object;
 +              struct commit *old_commit, *new_commit;
 +              struct commit_list *bases, *ent;
 +
 +              old_object = parse_object(old_sha1);
 +              new_object = parse_object(new_sha1);
 +
 +              if (!old_object || !new_object ||
 +                  old_object->type != OBJ_COMMIT ||
 +                  new_object->type != OBJ_COMMIT) {
 +                      error("bad sha1 objects for %s", name);
 +                      return "bad ref";
 +              }
 +              old_commit = (struct commit *)old_object;
 +              new_commit = (struct commit *)new_object;
 +              bases = get_merge_bases(old_commit, new_commit, 1);
 +              for (ent = bases; ent; ent = ent->next)
 +                      if (!hashcmp(old_sha1, ent->item->object.sha1))
 +                              break;
 +              free_commit_list(bases);
 +              if (!ent) {
 +                      rp_error("denying non-fast-forward %s"
 +                               " (you should pull first)", name);
 +                      return "non-fast-forward";
 +              }
 +      }
 +      if (run_update_hook(cmd)) {
 +              rp_error("hook declined to update %s", name);
 +              return "hook declined";
 +      }
 +
 +      if (is_null_sha1(new_sha1)) {
 +              if (!parse_object(old_sha1)) {
 +                      rp_warning("Allowing deletion of corrupt ref.");
 +                      old_sha1 = NULL;
 +              }
 +              if (delete_ref(name, old_sha1, 0)) {
 +                      rp_error("failed to delete %s", name);
 +                      return "failed to delete";
 +              }
 +              return NULL; /* good */
 +      }
 +      else {
 +              lock = lock_any_ref_for_update(name, old_sha1, 0);
 +              if (!lock) {
 +                      rp_error("failed to lock %s", name);
 +                      return "failed to lock";
 +              }
 +              if (write_ref_sha1(lock, new_sha1, "push")) {
 +                      return "failed to write"; /* error() already called */
 +              }
 +              return NULL; /* good */
 +      }
 +}
 +
 +static char update_post_hook[] = "hooks/post-update";
 +
-       struct command *cmd_p;
++static void run_update_post_hook(struct command *commands)
 +{
-       for (argc = 0, cmd_p = cmd; cmd_p; cmd_p = cmd_p->next) {
-               if (cmd_p->error_string)
++      struct command *cmd;
 +      int argc;
 +      const char **argv;
 +      struct child_process proc;
 +
-       for (argc = 1, cmd_p = cmd; cmd_p; cmd_p = cmd_p->next) {
++      for (argc = 0, cmd = commands; cmd; cmd = cmd->next) {
++              if (cmd->error_string)
 +                      continue;
 +              argc++;
 +      }
 +      if (!argc || access(update_post_hook, X_OK) < 0)
 +              return;
 +      argv = xmalloc(sizeof(*argv) * (2 + argc));
 +      argv[0] = update_post_hook;
 +
-               if (cmd_p->error_string)
++      for (argc = 1, cmd = commands; cmd; cmd = cmd->next) {
 +              char *p;
-               p = xmalloc(strlen(cmd_p->ref_name) + 1);
-               strcpy(p, cmd_p->ref_name);
++              if (cmd->error_string)
 +                      continue;
- static void execute_commands(const char *unpacker_error)
++              p = xmalloc(strlen(cmd->ref_name) + 1);
++              strcpy(p, cmd->ref_name);
 +              argv[argc] = p;
 +              argc++;
 +      }
 +      argv[argc] = NULL;
 +
 +      memset(&proc, 0, sizeof(proc));
 +      proc.no_stdin = 1;
 +      proc.stdout_to_stderr = 1;
 +      proc.err = use_sideband ? -1 : 0;
 +      proc.argv = argv;
 +
 +      if (!start_command(&proc)) {
 +              if (use_sideband)
 +                      copy_to_sideband(proc.err, -1, NULL);
 +              finish_command(&proc);
 +      }
 +}
 +
-       struct command *cmd = 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)
 +{
-               while (cmd) {
++      struct command *cmd;
 +      unsigned char sha1[20];
 +
 +      if (unpacker_error) {
-                       cmd = cmd->next;
-               }
++              for (cmd = commands; cmd; cmd = cmd->next)
 +                      cmd->error_string = "n/a (unpacker error)";
-       if (run_receive_hook(pre_receive_hook)) {
-               while (cmd) {
 +              return;
 +      }
 +
-                       cmd = cmd->next;
-               }
++      if (run_receive_hook(commands, pre_receive_hook)) {
++              for (cmd = commands; cmd; cmd = cmd->next)
 +                      cmd->error_string = "pre-receive hook declined";
-       while (cmd) {
-               cmd->error_string = update(cmd);
-               cmd = cmd->next;
-       }
 +              return;
 +      }
 +
++      check_aliased_updates(commands);
++
 +      head_name = resolve_ref("HEAD", sha1, 0, NULL);
 +
- static void read_head_info(void)
++      for (cmd = commands; cmd; cmd = cmd->next)
++              if (!cmd->skip_update)
++                      cmd->error_string = update(cmd);
 +}
 +
-               cmd = xmalloc(sizeof(struct command) + len - 80);
++static struct command *read_head_info(void)
 +{
++      struct command *commands = NULL;
 +      struct command **p = &commands;
 +      for (;;) {
 +              static char line[1000];
 +              unsigned char old_sha1[20], new_sha1[20];
 +              struct command *cmd;
 +              char *refname;
 +              int len, reflen;
 +
 +              len = packet_read_line(0, line, sizeof(line));
 +              if (!len)
 +                      break;
 +              if (line[len-1] == '\n')
 +                      line[--len] = 0;
 +              if (len < 83 ||
 +                  line[40] != ' ' ||
 +                  line[81] != ' ' ||
 +                  get_sha1_hex(line, old_sha1) ||
 +                  get_sha1_hex(line + 41, new_sha1))
 +                      die("protocol error: expected old/new/ref, got '%s'",
 +                          line);
 +
 +              refname = line + 82;
 +              reflen = strlen(refname);
 +              if (reflen + 82 < len) {
 +                      if (strstr(refname + reflen + 1, "report-status"))
 +                              report_status = 1;
 +                      if (strstr(refname + reflen + 1, "side-band-64k"))
 +                              use_sideband = LARGE_PACKET_MAX;
 +              }
-               cmd->error_string = NULL;
-               cmd->next = NULL;
++              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);
- static void report(const char *unpack_status)
 +              *p = cmd;
 +              p = &cmd->next;
 +      }
++      return commands;
 +}
 +
 +static const char *parse_pack_header(struct pack_header *hdr)
 +{
 +      switch (read_pack_header(0, hdr)) {
 +      case PH_ERROR_EOF:
 +              return "eof before pack header was fully read";
 +
 +      case PH_ERROR_PACK_SIGNATURE:
 +              return "protocol error (pack signature mismatch detected)";
 +
 +      case PH_ERROR_PROTOCOL:
 +              return "protocol error (pack version unsupported)";
 +
 +      default:
 +              return "unknown error in parse_pack_header";
 +
 +      case 0:
 +              return NULL;
 +      }
 +}
 +
 +static const char *pack_lockfile;
 +
 +static const char *unpack(void)
 +{
 +      struct pack_header hdr;
 +      const char *hdr_err;
 +      char hdr_arg[38];
 +
 +      hdr_err = parse_pack_header(&hdr);
 +      if (hdr_err)
 +              return hdr_err;
 +      snprintf(hdr_arg, sizeof(hdr_arg),
 +                      "--pack_header=%"PRIu32",%"PRIu32,
 +                      ntohl(hdr.hdr_version), ntohl(hdr.hdr_entries));
 +
 +      if (ntohl(hdr.hdr_entries) < unpack_limit) {
 +              int code, i = 0;
 +              const char *unpacker[4];
 +              unpacker[i++] = "unpack-objects";
 +              if (receive_fsck_objects)
 +                      unpacker[i++] = "--strict";
 +              unpacker[i++] = hdr_arg;
 +              unpacker[i++] = NULL;
 +              code = run_command_v_opt(unpacker, RUN_GIT_CMD);
 +              if (!code)
 +                      return NULL;
 +              return "unpack-objects abnormal exit";
 +      } else {
 +              const char *keeper[7];
 +              int s, status, i = 0;
 +              char keep_arg[256];
 +              struct child_process ip;
 +
 +              s = sprintf(keep_arg, "--keep=receive-pack %"PRIuMAX" on ", (uintmax_t) getpid());
 +              if (gethostname(keep_arg + s, sizeof(keep_arg) - s))
 +                      strcpy(keep_arg + s, "localhost");
 +
 +              keeper[i++] = "index-pack";
 +              keeper[i++] = "--stdin";
 +              if (receive_fsck_objects)
 +                      keeper[i++] = "--strict";
 +              keeper[i++] = "--fix-thin";
 +              keeper[i++] = hdr_arg;
 +              keeper[i++] = keep_arg;
 +              keeper[i++] = NULL;
 +              memset(&ip, 0, sizeof(ip));
 +              ip.argv = keeper;
 +              ip.out = -1;
 +              ip.git_cmd = 1;
 +              status = start_command(&ip);
 +              if (status) {
 +                      return "index-pack fork failed";
 +              }
 +              pack_lockfile = index_pack_lockfile(ip.out);
 +              close(ip.out);
 +              status = finish_command(&ip);
 +              if (!status) {
 +                      reprepare_packed_git();
 +                      return NULL;
 +              }
 +              return "index-pack abnormal exit";
 +      }
 +}
 +
- static int delete_only(struct command *cmd)
++static void report(struct command *commands, const char *unpack_status)
 +{
 +      struct command *cmd;
 +      struct strbuf buf = STRBUF_INIT;
 +
 +      packet_buf_write(&buf, "unpack %s\n",
 +                       unpack_status ? unpack_status : "ok");
 +      for (cmd = commands; cmd; cmd = cmd->next) {
 +              if (!cmd->error_string)
 +                      packet_buf_write(&buf, "ok %s\n",
 +                                       cmd->ref_name);
 +              else
 +                      packet_buf_write(&buf, "ng %s %s\n",
 +                                       cmd->ref_name, cmd->error_string);
 +      }
 +      packet_buf_flush(&buf);
 +
 +      if (use_sideband)
 +              send_sideband(1, 1, buf.buf, buf.len, use_sideband);
 +      else
 +              safe_write(1, buf.buf, buf.len);
 +      strbuf_release(&buf);
 +}
 +
-       while (cmd) {
++static int delete_only(struct command *commands)
 +{
-               cmd = cmd->next;
++      struct command *cmd;
++      for (cmd = commands; cmd; cmd = cmd->next) {
 +              if (!is_null_sha1(cmd->new_sha1))
 +                      return 0;
-       read_head_info();
-       if (commands) {
 +      }
 +      return 1;
 +}
 +
 +static int add_refs_from_alternate(struct alternate_object_database *e, void *unused)
 +{
 +      char *other;
 +      size_t len;
 +      struct remote *remote;
 +      struct transport *transport;
 +      const struct ref *extra;
 +
 +      e->name[-1] = '\0';
 +      other = xstrdup(make_absolute_path(e->base));
 +      e->name[-1] = '/';
 +      len = strlen(other);
 +
 +      while (other[len-1] == '/')
 +              other[--len] = '\0';
 +      if (len < 8 || memcmp(other + len - 8, "/objects", 8))
 +              return 0;
 +      /* Is this a git repository with refs? */
 +      memcpy(other + len - 8, "/refs", 6);
 +      if (!is_directory(other))
 +              return 0;
 +      other[len - 8] = '\0';
 +      remote = remote_get(other);
 +      transport = transport_get(remote, other);
 +      for (extra = transport_get_remote_refs(transport);
 +           extra;
 +           extra = extra->next) {
 +              add_extra_ref(".have", extra->old_sha1, 0);
 +      }
 +      transport_disconnect(transport);
 +      free(other);
 +      return 0;
 +}
 +
 +static void add_alternate_refs(void)
 +{
 +      foreach_alt_odb(add_refs_from_alternate, NULL);
 +}
 +
 +int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 +{
 +      int advertise_refs = 0;
 +      int stateless_rpc = 0;
 +      int i;
 +      char *dir = NULL;
++      struct command *commands;
 +
 +      argv++;
 +      for (i = 1; i < argc; i++) {
 +              const char *arg = *argv++;
 +
 +              if (*arg == '-') {
 +                      if (!strcmp(arg, "--advertise-refs")) {
 +                              advertise_refs = 1;
 +                              continue;
 +                      }
 +                      if (!strcmp(arg, "--stateless-rpc")) {
 +                              stateless_rpc = 1;
 +                              continue;
 +                      }
 +
 +                      usage(receive_pack_usage);
 +              }
 +              if (dir)
 +                      usage(receive_pack_usage);
 +              dir = xstrdup(arg);
 +      }
 +      if (!dir)
 +              usage(receive_pack_usage);
 +
 +      setup_path();
 +
 +      if (!enter_repo(dir, 0))
 +              die("'%s' does not appear to be a git repository", dir);
 +
 +      if (is_repository_shallow())
 +              die("attempt to push into a shallow repository");
 +
 +      git_config(receive_pack_config, NULL);
 +
 +      if (0 <= transfer_unpack_limit)
 +              unpack_limit = transfer_unpack_limit;
 +      else if (0 <= receive_unpack_limit)
 +              unpack_limit = receive_unpack_limit;
 +
 +      if (advertise_refs || !stateless_rpc) {
 +              add_alternate_refs();
 +              write_head_info();
 +              clear_extra_refs();
 +
 +              /* EOF */
 +              packet_flush(1);
 +      }
 +      if (advertise_refs)
 +              return 0;
 +
-               execute_commands(unpack_status);
++      if ((commands = read_head_info()) != NULL) {
 +              const char *unpack_status = NULL;
 +
 +              if (!delete_only(commands))
 +                      unpack_status = unpack();
-                       report(unpack_status);
-               run_receive_hook(post_receive_hook);
++              execute_commands(commands, unpack_status);
 +              if (pack_lockfile)
 +                      unlink_or_warn(pack_lockfile);
 +              if (report_status)
++                      report(commands, unpack_status);
++              run_receive_hook(commands, post_receive_hook);
 +              run_update_post_hook(commands);
 +              if (auto_gc) {
 +                      const char *argv_gc_auto[] = {
 +                              "gc", "--auto", "--quiet", NULL,
 +                      };
 +                      run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 +              }
 +              if (auto_update_server_info)
 +                      update_server_info(0);
 +      }
 +      if (use_sideband)
 +              packet_flush(1);
 +      return 0;
 +}

diff --cc t/t5516-fetch-push.sh
index 6a37a4d993df3fa4958a719fdfdb82f0dd2de623,f0813e0d0b2c339ecbc251acf602b53e6abc97d9..b11da79c9cafebb5af572bd8e9f85dfc6f3c3f77
--- 1/t/t5516-fetch-push.sh
--- 2/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@@ -528,9 -538,10 +538,10 @@@ test_expect_success 'push does not upda
        mk_test heads/master &&
        mk_child child &&
        mkdir testrepo/.git/hooks &&
 -      echo exit 1 >testrepo/.git/hooks/pre-receive &&
 +      echo "#!/no/frobnication/today" >testrepo/.git/hooks/pre-receive &&
        chmod +x testrepo/.git/hooks/pre-receive &&
-       (cd child &&
+       (
+               cd child &&
                git pull .. master
                test_must_fail git push &&
                test $(git rev-parse master) != \
@@@ -660,54 -683,53 +683,103 @@@ test_expect_success 'push with branche
        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_expect_success 'push --porcelain' '
 +      mk_empty &&
 +      echo >.git/foo  "To testrepo" &&
 +      echo >>.git/foo "*      refs/heads/master:refs/remotes/origin/master    [new branch]"  &&
 +      echo >>.git/foo "Done" &&
 +      git push >.git/bar --porcelain  testrepo refs/heads/master:refs/remotes/origin/master &&
 +      (
 +              cd testrepo &&
 +              r=$(git show-ref -s --verify refs/remotes/origin/master) &&
 +              test "z$r" = "z$the_commit" &&
 +              test 1 = $(git for-each-ref refs/remotes/origin | wc -l)
 +      ) &&
 +      test_cmp .git/foo .git/bar
 +'
 +
 +test_expect_success 'push --porcelain bad url' '
 +      mk_empty &&
 +      test_must_fail git push >.git/bar --porcelain asdfasdfasd refs/heads/master:refs/remotes/origin/master &&
 +      test_must_fail grep -q Done .git/bar
 +'
 +
 +test_expect_success 'push --porcelain rejected' '
 +      mk_empty &&
 +      git push testrepo refs/heads/master:refs/remotes/origin/master &&
 +      (cd testrepo &&
 +              git reset --hard origin/master^
 +              git config receive.denyCurrentBranch true) &&
 +
 +      echo >.git/foo  "To testrepo"  &&
 +      echo >>.git/foo "!      refs/heads/master:refs/heads/master     [remote rejected] (branch is currently checked out)" &&
 +
 +      test_must_fail git push >.git/bar --porcelain  testrepo refs/heads/master:refs/heads/master &&
 +      test_cmp .git/foo .git/bar
 +'
 +
 +test_expect_success 'push --porcelain --dry-run rejected' '
 +      mk_empty &&
 +      git push testrepo refs/heads/master:refs/remotes/origin/master &&
 +      (cd testrepo &&
 +              git reset --hard origin/master
 +              git config receive.denyCurrentBranch true) &&
 +
 +      echo >.git/foo  "To testrepo"  &&
 +      echo >>.git/foo "!      refs/heads/master^:refs/heads/master    [rejected] (non-fast-forward)" &&
 +      echo >>.git/foo "Done" &&
 +
 +      test_must_fail git push >.git/bar --porcelain  --dry-run testrepo refs/heads/master^:refs/heads/master &&
 +      test_cmp .git/foo .git/bar
 +'
 +
  test_done