run-command.c

   1 #include "cache.h"
   2 #include "run-command.h"
   3 #include "exec_cmd.h"
   4 #include "sigchain.h"
   5 #include "argv-array.h"
   6
   7 #ifndef SHELL_PATH
   8 # define SHELL_PATH "/bin/sh"
   9 #endif
  10
  11 struct child_to_clean {
  12         pid_t pid;
  13         struct child_to_clean *next;
  14 };
  15 static struct child_to_clean *children_to_clean;
  16 static int installed_child_cleanup_handler;
  17
  18 static void cleanup_children(int sig)
  19 {
  20         while (children_to_clean) {
  21                 struct child_to_clean *p = children_to_clean;
  22                 children_to_clean = p->next;
  23                 kill(p->pid, sig);
  24                 free(p);
  25         }
  26 }
  27
  28 static void cleanup_children_on_signal(int sig)
  29 {
  30         cleanup_children(sig);
  31         sigchain_pop(sig);
  32         raise(sig);
  33 }
  34
  35 static void cleanup_children_on_exit(void)
  36 {
  37         cleanup_children(SIGTERM);
  38 }
  39
  40 static void mark_child_for_cleanup(pid_t pid)
  41 {
  42         struct child_to_clean *p = xmalloc(sizeof(*p));
  43         p->pid = pid;
  44         p->next = children_to_clean;
  45         children_to_clean = p;
  46
  47         if (!installed_child_cleanup_handler) {
  48                 atexit(cleanup_children_on_exit);
  49                 sigchain_push_common(cleanup_children_on_signal);
  50                 installed_child_cleanup_handler = 1;
  51         }
  52 }
  53
  54 static void clear_child_for_cleanup(pid_t pid)
  55 {
  56         struct child_to_clean **pp;
  57
  58         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
  59                 struct child_to_clean *clean_me = *pp;
  60
  61                 if (clean_me->pid == pid) {
  62                         *pp = clean_me->next;
  63                         free(clean_me);
  64                         return;
  65                 }
  66         }
  67 }
  68
  69 static inline void close_pair(int fd[2])
  70 {
  71         close(fd[0]);
  72         close(fd[1]);
  73 }
  74
  75 #ifndef WIN32
  76 static inline void dup_devnull(int to)
  77 {
  78         int fd = open("/dev/null", O_RDWR);
  79         dup2(fd, to);
  80         close(fd);
  81 }
  82 #endif
  83
  84 static char *locate_in_PATH(const char *file)
  85 {
  86         const char *p = getenv("PATH");
  87         struct strbuf buf = STRBUF_INIT;
  88
  89         if (!p || !*p)
  90                 return NULL;
  91
  92         while (1) {
  93                 const char *end = strchrnul(p, ':');
  94
  95                 strbuf_reset(&buf);
  96
  97                 /* POSIX specifies an empty entry as the current directory. */
  98                 if (end != p) {
  99                         strbuf_add(&buf, p, end - p);
 100                         strbuf_addch(&buf, '/');
 101                 }
 102                 strbuf_addstr(&buf, file);
 103
 104                 if (!access(buf.buf, F_OK))
 105                         return strbuf_detach(&buf, NULL);
 106
 107                 if (!*end)
 108                         break;
 109                 p = end + 1;
 110         }
 111
 112         strbuf_release(&buf);
 113         return NULL;
 114 }
 115
 116 static int exists_in_PATH(const char *file)
 117 {
 118         char *r = locate_in_PATH(file);
 119         free(r);
 120         return r != NULL;
 121 }
 122
 123 int sane_execvp(const char *file, char * const argv[])
 124 {
 125         if (!execvp(file, argv))
 126                 return 0; /* cannot happen ;-) */
 127
 128         /*
 129          * When a command can't be found because one of the directories
 130          * listed in $PATH is unsearchable, execvp reports EACCES, but
 131          * careful usability testing (read: analysis of occasional bug
 132          * reports) reveals that "No such file or directory" is more
 133          * intuitive.
 134          *
 135          * We avoid commands with "/", because execvp will not do $PATH
 136          * lookups in that case.
 137          *
 138          * The reassignment of EACCES to errno looks like a no-op below,
 139          * but we need to protect against exists_in_PATH overwriting errno.
 140          */
 141         if (errno == EACCES && !strchr(file, '/'))
 142                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 143         else if (errno == ENOTDIR && !strchr(file, '/'))
 144                 errno = ENOENT;
 145         return -1;
 146 }
 147
 148 static const char **prepare_shell_cmd(const char **argv)
 149 {
 150         int argc, nargc = 0;
 151         const char **nargv;
 152
 153         for (argc = 0; argv[argc]; argc++)
 154                 ; /* just counting */
 155         /* +1 for NULL, +3 for "sh -c" plus extra $0 */
 156         nargv = xmalloc(sizeof(*nargv) * (argc + 1 + 3));
 157
 158         if (argc < 1)
 159                 die("BUG: shell command is empty");
 160
 161         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 162 #ifndef WIN32
 163                 nargv[nargc++] = SHELL_PATH;
 164 #else
 165                 nargv[nargc++] = "sh";
 166 #endif
 167                 nargv[nargc++] = "-c";
 168
 169                 if (argc < 2)
 170                         nargv[nargc++] = argv[0];
 171                 else {
 172                         struct strbuf arg0 = STRBUF_INIT;
 173                         strbuf_addf(&arg0, "%s \"$@\"", argv[0]);
 174                         nargv[nargc++] = strbuf_detach(&arg0, NULL);
 175                 }
 176         }
 177
 178         for (argc = 0; argv[argc]; argc++)
 179                 nargv[nargc++] = argv[argc];
 180         nargv[nargc] = NULL;
 181
 182         return nargv;
 183 }
 184
 185 #ifndef WIN32
 186 static int execv_shell_cmd(const char **argv)
 187 {
 188         const char **nargv = prepare_shell_cmd(argv);
 189         trace_argv_printf(nargv, "trace: exec:");
 190         sane_execvp(nargv[0], (char **)nargv);
 191         free(nargv);
 192         return -1;
 193 }
 194 #endif
 195
 196 #ifndef WIN32
 197 static int child_err = 2;
 198 static int child_notifier = -1;
 199
 200 static void notify_parent(void)
 201 {
 202         /*
 203          * execvp failed.  If possible, we'd like to let start_command
 204          * know, so failures like ENOENT can be handled right away; but
 205          * otherwise, finish_command will still report the error.
 206          */
 207         xwrite(child_notifier, "", 1);
 208 }
 209
 210 static NORETURN void die_child(const char *err, va_list params)
 211 {
 212         vwritef(child_err, "fatal: ", err, params);
 213         exit(128);
 214 }
 215
 216 static void error_child(const char *err, va_list params)
 217 {
 218         vwritef(child_err, "error: ", err, params);
 219 }
 220 #endif
 221
 222 static inline void set_cloexec(int fd)
 223 {
 224         int flags = fcntl(fd, F_GETFD);
 225         if (flags >= 0)
 226                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 227 }
 228
 229 static int wait_or_whine(pid_t pid, const char *argv0)
 230 {
 231         int status, code = -1;
 232         pid_t waiting;
 233         int failed_errno = 0;
 234
 235         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 236                 ;       /* nothing */
 237
 238         if (waiting < 0) {
 239                 failed_errno = errno;
 240                 error("waitpid for %s failed: %s", argv0, strerror(errno));
 241         } else if (waiting != pid) {
 242                 error("waitpid is confused (%s)", argv0);
 243         } else if (WIFSIGNALED(status)) {
 244                 code = WTERMSIG(status);
 245                 if (code != SIGINT && code != SIGQUIT)
 246                         error("%s died of signal %d", argv0, code);
 247                 /*
 248                  * This return value is chosen so that code & 0xff
 249                  * mimics the exit code that a POSIX shell would report for
 250                  * a program that died from this signal.
 251                  */
 252                 code += 128;
 253         } else if (WIFEXITED(status)) {
 254                 code = WEXITSTATUS(status);
 255                 /*
 256                  * Convert special exit code when execvp failed.
 257                  */
 258                 if (code == 127) {
 259                         code = -1;
 260                         failed_errno = ENOENT;
 261                 }
 262         } else {
 263                 error("waitpid is confused (%s)", argv0);
 264         }
 265
 266         clear_child_for_cleanup(pid);
 267
 268         errno = failed_errno;
 269         return code;
 270 }
 271
 272 int start_command(struct child_process *cmd)
 273 {
 274         int need_in, need_out, need_err;
 275         int fdin[2], fdout[2], fderr[2];
 276         int failed_errno;
 277         char *str;
 278
 279         /*
 280          * In case of errors we must keep the promise to close FDs
 281          * that have been passed in via ->in and ->out.
 282          */
 283
 284         need_in = !cmd->no_stdin && cmd->in < 0;
 285         if (need_in) {
 286                 if (pipe(fdin) < 0) {
 287                         failed_errno = errno;
 288                         if (cmd->out > 0)
 289                                 close(cmd->out);
 290                         str = "standard input";
 291                         goto fail_pipe;
 292                 }
 293                 cmd->in = fdin[1];
 294         }
 295
 296         need_out = !cmd->no_stdout
 297                 && !cmd->stdout_to_stderr
 298                 && cmd->out < 0;
 299         if (need_out) {
 300                 if (pipe(fdout) < 0) {
 301                         failed_errno = errno;
 302                         if (need_in)
 303                                 close_pair(fdin);
 304                         else if (cmd->in)
 305                                 close(cmd->in);
 306                         str = "standard output";
 307                         goto fail_pipe;
 308                 }
 309                 cmd->out = fdout[0];
 310         }
 311
 312         need_err = !cmd->no_stderr && cmd->err < 0;
 313         if (need_err) {
 314                 if (pipe(fderr) < 0) {
 315                         failed_errno = errno;
 316                         if (need_in)
 317                                 close_pair(fdin);
 318                         else if (cmd->in)
 319                                 close(cmd->in);
 320                         if (need_out)
 321                                 close_pair(fdout);
 322                         else if (cmd->out)
 323                                 close(cmd->out);
 324                         str = "standard error";
 325 fail_pipe:
 326                         error("cannot create %s pipe for %s: %s",
 327                                 str, cmd->argv[0], strerror(failed_errno));
 328                         errno = failed_errno;
 329                         return -1;
 330                 }
 331                 cmd->err = fderr[0];
 332         }
 333
 334         trace_argv_printf(cmd->argv, "trace: run_command:");
 335         fflush(NULL);
 336
 337 #ifndef WIN32
 338 {
 339         int notify_pipe[2];
 340         if (pipe(notify_pipe))
 341                 notify_pipe[0] = notify_pipe[1] = -1;
 342
 343         cmd->pid = fork();
 344         failed_errno = errno;
 345         if (!cmd->pid) {
 346                 /*
 347                  * Redirect the channel to write syscall error messages to
 348                  * before redirecting the process's stderr so that all die()
 349                  * in subsequent call paths use the parent's stderr.
 350                  */
 351                 if (cmd->no_stderr || need_err) {
 352                         child_err = dup(2);
 353                         set_cloexec(child_err);
 354                 }
 355                 set_die_routine(die_child);
 356                 set_error_routine(error_child);
 357
 358                 close(notify_pipe[0]);
 359                 set_cloexec(notify_pipe[1]);
 360                 child_notifier = notify_pipe[1];
 361                 atexit(notify_parent);
 362
 363                 if (cmd->no_stdin)
 364                         dup_devnull(0);
 365                 else if (need_in) {
 366                         dup2(fdin[0], 0);
 367                         close_pair(fdin);
 368                 } else if (cmd->in) {
 369                         dup2(cmd->in, 0);
 370                         close(cmd->in);
 371                 }
 372
 373                 if (cmd->no_stderr)
 374                         dup_devnull(2);
 375                 else if (need_err) {
 376                         dup2(fderr[1], 2);
 377                         close_pair(fderr);
 378                 } else if (cmd->err > 1) {
 379                         dup2(cmd->err, 2);
 380                         close(cmd->err);
 381                 }
 382
 383                 if (cmd->no_stdout)
 384                         dup_devnull(1);
 385                 else if (cmd->stdout_to_stderr)
 386                         dup2(2, 1);
 387                 else if (need_out) {
 388                         dup2(fdout[1], 1);
 389                         close_pair(fdout);
 390                 } else if (cmd->out > 1) {
 391                         dup2(cmd->out, 1);
 392                         close(cmd->out);
 393                 }
 394
 395                 if (cmd->dir && chdir(cmd->dir))
 396                         die_errno("exec '%s': cd to '%s' failed", cmd->argv[0],
 397                             cmd->dir);
 398                 if (cmd->env) {
 399                         for (; *cmd->env; cmd->env++) {
 400                                 if (strchr(*cmd->env, '='))
 401                                         putenv((char *)*cmd->env);
 402                                 else
 403                                         unsetenv(*cmd->env);
 404                         }
 405                 }
 406                 if (cmd->git_cmd) {
 407                         execv_git_cmd(cmd->argv);
 408                 } else if (cmd->use_shell) {
 409                         execv_shell_cmd(cmd->argv);
 410                 } else {
 411                         sane_execvp(cmd->argv[0], (char *const*) cmd->argv);
 412                 }
 413                 if (errno == ENOENT) {
 414                         if (!cmd->silent_exec_failure)
 415                                 error("cannot run %s: %s", cmd->argv[0],
 416                                         strerror(ENOENT));
 417                         exit(127);
 418                 } else {
 419                         die_errno("cannot exec '%s'", cmd->argv[0]);
 420                 }
 421         }
 422         if (cmd->pid < 0)
 423                 error("cannot fork() for %s: %s", cmd->argv[0],
 424                         strerror(errno));
 425         else if (cmd->clean_on_exit)
 426                 mark_child_for_cleanup(cmd->pid);
 427
 428         /*
 429          * Wait for child's execvp. If the execvp succeeds (or if fork()
 430          * failed), EOF is seen immediately by the parent. Otherwise, the
 431          * child process sends a single byte.
 432          * Note that use of this infrastructure is completely advisory,
 433          * therefore, we keep error checks minimal.
 434          */
 435         close(notify_pipe[1]);
 436         if (read(notify_pipe[0], &notify_pipe[1], 1) == 1) {
 437                 /*
 438                  * At this point we know that fork() succeeded, but execvp()
 439                  * failed. Errors have been reported to our stderr.
 440                  */
 441                 wait_or_whine(cmd->pid, cmd->argv[0]);
 442                 failed_errno = errno;
 443                 cmd->pid = -1;
 444         }
 445         close(notify_pipe[0]);
 446
 447 }
 448 #else
 449 {
 450         int fhin = 0, fhout = 1, fherr = 2;
 451         const char **sargv = cmd->argv;
 452         char **env = environ;
 453
 454         if (cmd->no_stdin)
 455                 fhin = open("/dev/null", O_RDWR);
 456         else if (need_in)
 457                 fhin = dup(fdin[0]);
 458         else if (cmd->in)
 459                 fhin = dup(cmd->in);
 460
 461         if (cmd->no_stderr)
 462                 fherr = open("/dev/null", O_RDWR);
 463         else if (need_err)
 464                 fherr = dup(fderr[1]);
 465         else if (cmd->err > 2)
 466                 fherr = dup(cmd->err);
 467
 468         if (cmd->no_stdout)
 469                 fhout = open("/dev/null", O_RDWR);
 470         else if (cmd->stdout_to_stderr)
 471                 fhout = dup(fherr);
 472         else if (need_out)
 473                 fhout = dup(fdout[1]);
 474         else if (cmd->out > 1)
 475                 fhout = dup(cmd->out);
 476
 477         if (cmd->env)
 478                 env = make_augmented_environ(cmd->env);
 479
 480         if (cmd->git_cmd) {
 481                 cmd->argv = prepare_git_cmd(cmd->argv);
 482         } else if (cmd->use_shell) {
 483                 cmd->argv = prepare_shell_cmd(cmd->argv);
 484         }
 485
 486         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, env, cmd->dir,
 487                                   fhin, fhout, fherr);
 488         failed_errno = errno;
 489         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 490                 error("cannot spawn %s: %s", cmd->argv[0], strerror(errno));
 491         if (cmd->clean_on_exit && cmd->pid >= 0)
 492                 mark_child_for_cleanup(cmd->pid);
 493
 494         if (cmd->env)
 495                 free_environ(env);
 496         if (cmd->git_cmd)
 497                 free(cmd->argv);
 498
 499         cmd->argv = sargv;
 500         if (fhin != 0)
 501                 close(fhin);
 502         if (fhout != 1)
 503                 close(fhout);
 504         if (fherr != 2)
 505                 close(fherr);
 506 }
 507 #endif
 508
 509         if (cmd->pid < 0) {
 510                 if (need_in)
 511                         close_pair(fdin);
 512                 else if (cmd->in)
 513                         close(cmd->in);
 514                 if (need_out)
 515                         close_pair(fdout);
 516                 else if (cmd->out)
 517                         close(cmd->out);
 518                 if (need_err)
 519                         close_pair(fderr);
 520                 else if (cmd->err)
 521                         close(cmd->err);
 522                 errno = failed_errno;
 523                 return -1;
 524         }
 525
 526         if (need_in)
 527                 close(fdin[0]);
 528         else if (cmd->in)
 529                 close(cmd->in);
 530
 531         if (need_out)
 532                 close(fdout[1]);
 533         else if (cmd->out)
 534                 close(cmd->out);
 535
 536         if (need_err)
 537                 close(fderr[1]);
 538         else if (cmd->err)
 539                 close(cmd->err);
 540
 541         return 0;
 542 }
 543
 544 int finish_command(struct child_process *cmd)
 545 {
 546         return wait_or_whine(cmd->pid, cmd->argv[0]);
 547 }
 548
 549 int run_command(struct child_process *cmd)
 550 {
 551         int code = start_command(cmd);
 552         if (code)
 553                 return code;
 554         return finish_command(cmd);
 555 }
 556
 557 static void prepare_run_command_v_opt(struct child_process *cmd,
 558                                       const char **argv,
 559                                       int opt)
 560 {
 561         memset(cmd, 0, sizeof(*cmd));
 562         cmd->argv = argv;
 563         cmd->no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 564         cmd->git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 565         cmd->stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 566         cmd->silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 567         cmd->use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 568         cmd->clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 569 }
 570
 571 int run_command_v_opt(const char **argv, int opt)
 572 {
 573         struct child_process cmd;
 574         prepare_run_command_v_opt(&cmd, argv, opt);
 575         return run_command(&cmd);
 576 }
 577
 578 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 579 {
 580         struct child_process cmd;
 581         prepare_run_command_v_opt(&cmd, argv, opt);
 582         cmd.dir = dir;
 583         cmd.env = env;
 584         return run_command(&cmd);
 585 }
 586
 587 #ifndef NO_PTHREADS
 588 static pthread_t main_thread;
 589 static int main_thread_set;
 590 static pthread_key_t async_key;
 591 static pthread_key_t async_die_counter;
 592
 593 static void *run_thread(void *data)
 594 {
 595         struct async *async = data;
 596         intptr_t ret;
 597
 598         pthread_setspecific(async_key, async);
 599         ret = async->proc(async->proc_in, async->proc_out, async->data);
 600         return (void *)ret;
 601 }
 602
 603 static NORETURN void die_async(const char *err, va_list params)
 604 {
 605         vreportf("fatal: ", err, params);
 606
 607         if (!pthread_equal(main_thread, pthread_self())) {
 608                 struct async *async = pthread_getspecific(async_key);
 609                 if (async->proc_in >= 0)
 610                         close(async->proc_in);
 611                 if (async->proc_out >= 0)
 612                         close(async->proc_out);
 613                 pthread_exit((void *)128);
 614         }
 615
 616         exit(128);
 617 }
 618
 619 static int async_die_is_recursing(void)
 620 {
 621         void *ret = pthread_getspecific(async_die_counter);
 622         pthread_setspecific(async_die_counter, (void *)1);
 623         return ret != NULL;
 624 }
 625
 626 #endif
 627
 628 int start_async(struct async *async)
 629 {
 630         int need_in, need_out;
 631         int fdin[2], fdout[2];
 632         int proc_in, proc_out;
 633
 634         need_in = async->in < 0;
 635         if (need_in) {
 636                 if (pipe(fdin) < 0) {
 637                         if (async->out > 0)
 638                                 close(async->out);
 639                         return error("cannot create pipe: %s", strerror(errno));
 640                 }
 641                 async->in = fdin[1];
 642         }
 643
 644         need_out = async->out < 0;
 645         if (need_out) {
 646                 if (pipe(fdout) < 0) {
 647                         if (need_in)
 648                                 close_pair(fdin);
 649                         else if (async->in)
 650                                 close(async->in);
 651                         return error("cannot create pipe: %s", strerror(errno));
 652                 }
 653                 async->out = fdout[0];
 654         }
 655
 656         if (need_in)
 657                 proc_in = fdin[0];
 658         else if (async->in)
 659                 proc_in = async->in;
 660         else
 661                 proc_in = -1;
 662
 663         if (need_out)
 664                 proc_out = fdout[1];
 665         else if (async->out)
 666                 proc_out = async->out;
 667         else
 668                 proc_out = -1;
 669
 670 #ifdef NO_PTHREADS
 671         /* Flush stdio before fork() to avoid cloning buffers */
 672         fflush(NULL);
 673
 674         async->pid = fork();
 675         if (async->pid < 0) {
 676                 error("fork (async) failed: %s", strerror(errno));
 677                 goto error;
 678         }
 679         if (!async->pid) {
 680                 if (need_in)
 681                         close(fdin[1]);
 682                 if (need_out)
 683                         close(fdout[0]);
 684                 exit(!!async->proc(proc_in, proc_out, async->data));
 685         }
 686
 687         mark_child_for_cleanup(async->pid);
 688
 689         if (need_in)
 690                 close(fdin[0]);
 691         else if (async->in)
 692                 close(async->in);
 693
 694         if (need_out)
 695                 close(fdout[1]);
 696         else if (async->out)
 697                 close(async->out);
 698 #else
 699         if (!main_thread_set) {
 700                 /*
 701                  * We assume that the first time that start_async is called
 702                  * it is from the main thread.
 703                  */
 704                 main_thread_set = 1;
 705                 main_thread = pthread_self();
 706                 pthread_key_create(&async_key, NULL);
 707                 pthread_key_create(&async_die_counter, NULL);
 708                 set_die_routine(die_async);
 709                 set_die_is_recursing_routine(async_die_is_recursing);
 710         }
 711
 712         if (proc_in >= 0)
 713                 set_cloexec(proc_in);
 714         if (proc_out >= 0)
 715                 set_cloexec(proc_out);
 716         async->proc_in = proc_in;
 717         async->proc_out = proc_out;
 718         {
 719                 int err = pthread_create(&async->tid, NULL, run_thread, async);
 720                 if (err) {
 721                         error("cannot create thread: %s", strerror(err));
 722                         goto error;
 723                 }
 724         }
 725 #endif
 726         return 0;
 727
 728 error:
 729         if (need_in)
 730                 close_pair(fdin);
 731         else if (async->in)
 732                 close(async->in);
 733
 734         if (need_out)
 735                 close_pair(fdout);
 736         else if (async->out)
 737                 close(async->out);
 738         return -1;
 739 }
 740
 741 int finish_async(struct async *async)
 742 {
 743 #ifdef NO_PTHREADS
 744         return wait_or_whine(async->pid, "child process");
 745 #else
 746         void *ret = (void *)(intptr_t)(-1);
 747
 748         if (pthread_join(async->tid, &ret))
 749                 error("pthread_join failed");
 750         return (int)(intptr_t)ret;
 751 #endif
 752 }
 753
 754 char *find_hook(const char *name)
 755 {
 756         char *path = git_path("hooks/%s", name);
 757         if (access(path, X_OK) < 0)
 758                 path = NULL;
 759
 760         return path;
 761 }
 762
 763 int run_hook(const char *index_file, const char *name, ...)
 764 {
 765         struct child_process hook;
 766         struct argv_array argv = ARGV_ARRAY_INIT;
 767         const char *p, *env[2];
 768         char index[PATH_MAX];
 769         va_list args;
 770         int ret;
 771
 772         p = find_hook(name);
 773         if (!p)
 774                 return 0;
 775
 776         argv_array_push(&argv, p);
 777
 778         va_start(args, name);
 779         while ((p = va_arg(args, const char *)))
 780                 argv_array_push(&argv, p);
 781         va_end(args);
 782
 783         memset(&hook, 0, sizeof(hook));
 784         hook.argv = argv.argv;
 785         hook.no_stdin = 1;
 786         hook.stdout_to_stderr = 1;
 787         if (index_file) {
 788                 snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
 789                 env[0] = index;
 790                 env[1] = NULL;
 791                 hook.env = env;
 792         }
 793
 794         ret = run_command(&hook);
 795         argv_array_clear(&argv);
 796         return ret;
 797 }