builtin/revert.c

   1 #include "cache.h"
   2 #include "builtin.h"
   3 #include "object.h"
   4 #include "commit.h"
   5 #include "tag.h"
   6 #include "run-command.h"
   7 #include "exec_cmd.h"
   8 #include "utf8.h"
   9 #include "parse-options.h"
  10 #include "cache-tree.h"
  11 #include "diff.h"
  12 #include "revision.h"
  13 #include "rerere.h"
  14 #include "merge-recursive.h"
  15 #include "refs.h"
  16 #include "dir.h"
  17 #include "sequencer.h"
  18
  19 /*
  20  * This implements the builtins revert and cherry-pick.
  21  *
  22  * Copyright (c) 2007 Johannes E. Schindelin
  23  *
  24  * Based on git-revert.sh, which is
  25  *
  26  * Copyright (c) 2005 Linus Torvalds
  27  * Copyright (c) 2005 Junio C Hamano
  28  */
  29
  30 static const char * const revert_usage[] = {
  31         "git revert [options] <commit-ish>",
  32         "git revert <subcommand>",
  33         NULL
  34 };
  35
  36 static const char * const cherry_pick_usage[] = {
  37         "git cherry-pick [options] <commit-ish>",
  38         "git cherry-pick <subcommand>",
  39         NULL
  40 };
  41
  42 enum replay_action { REVERT, CHERRY_PICK };
  43 enum replay_subcommand {
  44         REPLAY_NONE,
  45         REPLAY_REMOVE_STATE,
  46         REPLAY_CONTINUE,
  47         REPLAY_ROLLBACK
  48 };
  49
  50 struct replay_opts {
  51         enum replay_action action;
  52         enum replay_subcommand subcommand;
  53
  54         /* Boolean options */
  55         int edit;
  56         int record_origin;
  57         int no_commit;
  58         int signoff;
  59         int allow_ff;
  60         int allow_rerere_auto;
  61
  62         int mainline;
  63         int commit_argc;
  64         const char **commit_argv;
  65
  66         /* Merge strategy */
  67         const char *strategy;
  68         const char **xopts;
  69         size_t xopts_nr, xopts_alloc;
  70 };
  71
  72 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
  73
  74 static const char *action_name(const struct replay_opts *opts)
  75 {
  76         return opts->action == REVERT ? "revert" : "cherry-pick";
  77 }
  78
  79 static char *get_encoding(const char *message);
  80
  81 static const char * const *revert_or_cherry_pick_usage(struct replay_opts *opts)
  82 {
  83         return opts->action == REVERT ? revert_usage : cherry_pick_usage;
  84 }
  85
  86 static int option_parse_x(const struct option *opt,
  87                           const char *arg, int unset)
  88 {
  89         struct replay_opts **opts_ptr = opt->value;
  90         struct replay_opts *opts = *opts_ptr;
  91
  92         if (unset)
  93                 return 0;
  94
  95         ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
  96         opts->xopts[opts->xopts_nr++] = xstrdup(arg);
  97         return 0;
  98 }
  99
 100 static void verify_opt_compatible(const char *me, const char *base_opt, ...)
 101 {
 102         const char *this_opt;
 103         va_list ap;
 104
 105         va_start(ap, base_opt);
 106         while ((this_opt = va_arg(ap, const char *))) {
 107                 if (va_arg(ap, int))
 108                         break;
 109         }
 110         va_end(ap);
 111
 112         if (this_opt)
 113                 die(_("%s: %s cannot be used with %s"), me, this_opt, base_opt);
 114 }
 115
 116 static void verify_opt_mutually_compatible(const char *me, ...)
 117 {
 118         const char *opt1, *opt2 = NULL;
 119         va_list ap;
 120
 121         va_start(ap, me);
 122         while ((opt1 = va_arg(ap, const char *))) {
 123                 if (va_arg(ap, int))
 124                         break;
 125         }
 126         if (opt1) {
 127                 while ((opt2 = va_arg(ap, const char *))) {
 128                         if (va_arg(ap, int))
 129                                 break;
 130                 }
 131         }
 132
 133         if (opt1 && opt2)
 134                 die(_("%s: %s cannot be used with %s"), me, opt1, opt2);
 135 }
 136
 137 static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 138 {
 139         const char * const * usage_str = revert_or_cherry_pick_usage(opts);
 140         const char *me = action_name(opts);
 141         int remove_state = 0;
 142         int contin = 0;
 143         int rollback = 0;
 144         struct option options[] = {
 145                 OPT_BOOLEAN(0, "quit", &remove_state, "end revert or cherry-pick sequence"),
 146                 OPT_BOOLEAN(0, "continue", &contin, "resume revert or cherry-pick sequence"),
 147                 OPT_BOOLEAN(0, "abort", &rollback, "cancel revert or cherry-pick sequence"),
 148                 OPT_BOOLEAN('n', "no-commit", &opts->no_commit, "don't automatically commit"),
 149                 OPT_BOOLEAN('e', "edit", &opts->edit, "edit the commit message"),
 150                 OPT_NOOP_NOARG('r', NULL),
 151                 OPT_BOOLEAN('s', "signoff", &opts->signoff, "add Signed-off-by:"),
 152                 OPT_INTEGER('m', "mainline", &opts->mainline, "parent number"),
 153                 OPT_RERERE_AUTOUPDATE(&opts->allow_rerere_auto),
 154                 OPT_STRING(0, "strategy", &opts->strategy, "strategy", "merge strategy"),
 155                 OPT_CALLBACK('X', "strategy-option", &opts, "option",
 156                         "option for merge strategy", option_parse_x),
 157                 OPT_END(),
 158                 OPT_END(),
 159                 OPT_END(),
 160         };
 161
 162         if (opts->action == CHERRY_PICK) {
 163                 struct option cp_extra[] = {
 164                         OPT_BOOLEAN('x', NULL, &opts->record_origin, "append commit name"),
 165                         OPT_BOOLEAN(0, "ff", &opts->allow_ff, "allow fast-forward"),
 166                         OPT_END(),
 167                 };
 168                 if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))
 169                         die(_("program error"));
 170         }
 171
 172         opts->commit_argc = parse_options(argc, argv, NULL, options, usage_str,
 173                                         PARSE_OPT_KEEP_ARGV0 |
 174                                         PARSE_OPT_KEEP_UNKNOWN);
 175
 176         /* Check for incompatible subcommands */
 177         verify_opt_mutually_compatible(me,
 178                                 "--quit", remove_state,
 179                                 "--continue", contin,
 180                                 "--abort", rollback,
 181                                 NULL);
 182
 183         /* Set the subcommand */
 184         if (remove_state)
 185                 opts->subcommand = REPLAY_REMOVE_STATE;
 186         else if (contin)
 187                 opts->subcommand = REPLAY_CONTINUE;
 188         else if (rollback)
 189                 opts->subcommand = REPLAY_ROLLBACK;
 190         else
 191                 opts->subcommand = REPLAY_NONE;
 192
 193         /* Check for incompatible command line arguments */
 194         if (opts->subcommand != REPLAY_NONE) {
 195                 char *this_operation;
 196                 if (opts->subcommand == REPLAY_REMOVE_STATE)
 197                         this_operation = "--quit";
 198                 else if (opts->subcommand == REPLAY_CONTINUE)
 199                         this_operation = "--continue";
 200                 else {
 201                         assert(opts->subcommand == REPLAY_ROLLBACK);
 202                         this_operation = "--abort";
 203                 }
 204
 205                 verify_opt_compatible(me, this_operation,
 206                                 "--no-commit", opts->no_commit,
 207                                 "--signoff", opts->signoff,
 208                                 "--mainline", opts->mainline,
 209                                 "--strategy", opts->strategy ? 1 : 0,
 210                                 "--strategy-option", opts->xopts ? 1 : 0,
 211                                 "-x", opts->record_origin,
 212                                 "--ff", opts->allow_ff,
 213                                 NULL);
 214         }
 215
 216         else if (opts->commit_argc < 2)
 217                 usage_with_options(usage_str, options);
 218
 219         if (opts->allow_ff)
 220                 verify_opt_compatible(me, "--ff",
 221                                 "--signoff", opts->signoff,
 222                                 "--no-commit", opts->no_commit,
 223                                 "-x", opts->record_origin,
 224                                 "--edit", opts->edit,
 225                                 NULL);
 226         opts->commit_argv = argv;
 227 }
 228
 229 struct commit_message {
 230         char *parent_label;
 231         const char *label;
 232         const char *subject;
 233         char *reencoded_message;
 234         const char *message;
 235 };
 236
 237 static int get_message(struct commit *commit, struct commit_message *out)
 238 {
 239         const char *encoding;
 240         const char *abbrev, *subject;
 241         int abbrev_len, subject_len;
 242         char *q;
 243
 244         if (!commit->buffer)
 245                 return -1;
 246         encoding = get_encoding(commit->buffer);
 247         if (!encoding)
 248                 encoding = "UTF-8";
 249         if (!git_commit_encoding)
 250                 git_commit_encoding = "UTF-8";
 251
 252         out->reencoded_message = NULL;
 253         out->message = commit->buffer;
 254         if (strcmp(encoding, git_commit_encoding))
 255                 out->reencoded_message = reencode_string(commit->buffer,
 256                                         git_commit_encoding, encoding);
 257         if (out->reencoded_message)
 258                 out->message = out->reencoded_message;
 259
 260         abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
 261         abbrev_len = strlen(abbrev);
 262
 263         subject_len = find_commit_subject(out->message, &subject);
 264
 265         out->parent_label = xmalloc(strlen("parent of ") + abbrev_len +
 266                               strlen("... ") + subject_len + 1);
 267         q = out->parent_label;
 268         q = mempcpy(q, "parent of ", strlen("parent of "));
 269         out->label = q;
 270         q = mempcpy(q, abbrev, abbrev_len);
 271         q = mempcpy(q, "... ", strlen("... "));
 272         out->subject = q;
 273         q = mempcpy(q, subject, subject_len);
 274         *q = '\0';
 275         return 0;
 276 }
 277
 278 static void free_message(struct commit_message *msg)
 279 {
 280         free(msg->parent_label);
 281         free(msg->reencoded_message);
 282 }
 283
 284 static char *get_encoding(const char *message)
 285 {
 286         const char *p = message, *eol;
 287
 288         while (*p && *p != '\n') {
 289                 for (eol = p + 1; *eol && *eol != '\n'; eol++)
 290                         ; /* do nothing */
 291                 if (!prefixcmp(p, "encoding ")) {
 292                         char *result = xmalloc(eol - 8 - p);
 293                         strlcpy(result, p + 9, eol - 8 - p);
 294                         return result;
 295                 }
 296                 p = eol;
 297                 if (*p == '\n')
 298                         p++;
 299         }
 300         return NULL;
 301 }
 302
 303 static void write_cherry_pick_head(struct commit *commit, const char *pseudoref)
 304 {
 305         const char *filename;
 306         int fd;
 307         struct strbuf buf = STRBUF_INIT;
 308
 309         strbuf_addf(&buf, "%s\n", sha1_to_hex(commit->object.sha1));
 310
 311         filename = git_path("%s", pseudoref);
 312         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 313         if (fd < 0)
 314                 die_errno(_("Could not open '%s' for writing"), filename);
 315         if (write_in_full(fd, buf.buf, buf.len) != buf.len || close(fd))
 316                 die_errno(_("Could not write to '%s'"), filename);
 317         strbuf_release(&buf);
 318 }
 319
 320 static void print_advice(int show_hint)
 321 {
 322         char *msg = getenv("GIT_CHERRY_PICK_HELP");
 323
 324         if (msg) {
 325                 fprintf(stderr, "%s\n", msg);
 326                 /*
 327                  * A conflict has occured but the porcelain
 328                  * (typically rebase --interactive) wants to take care
 329                  * of the commit itself so remove CHERRY_PICK_HEAD
 330                  */
 331                 unlink(git_path("CHERRY_PICK_HEAD"));
 332                 return;
 333         }
 334
 335         if (show_hint)
 336                 advise(_("after resolving the conflicts, mark the corrected paths\n"
 337                          "with 'git add <paths>' or 'git rm <paths>'\n"
 338                          "and commit the result with 'git commit'"));
 339 }
 340
 341 static void write_message(struct strbuf *msgbuf, const char *filename)
 342 {
 343         static struct lock_file msg_file;
 344
 345         int msg_fd = hold_lock_file_for_update(&msg_file, filename,
 346                                                LOCK_DIE_ON_ERROR);
 347         if (write_in_full(msg_fd, msgbuf->buf, msgbuf->len) < 0)
 348                 die_errno(_("Could not write to %s"), filename);
 349         strbuf_release(msgbuf);
 350         if (commit_lock_file(&msg_file) < 0)
 351                 die(_("Error wrapping up %s"), filename);
 352 }
 353
 354 static struct tree *empty_tree(void)
 355 {
 356         return lookup_tree((const unsigned char *)EMPTY_TREE_SHA1_BIN);
 357 }
 358
 359 static int error_dirty_index(struct replay_opts *opts)
 360 {
 361         if (read_cache_unmerged())
 362                 return error_resolve_conflict(action_name(opts));
 363
 364         /* Different translation strings for cherry-pick and revert */
 365         if (opts->action == CHERRY_PICK)
 366                 error(_("Your local changes would be overwritten by cherry-pick."));
 367         else
 368                 error(_("Your local changes would be overwritten by revert."));
 369
 370         if (advice_commit_before_merge)
 371                 advise(_("Commit your changes or stash them to proceed."));
 372         return -1;
 373 }
 374
 375 static int fast_forward_to(const unsigned char *to, const unsigned char *from)
 376 {
 377         struct ref_lock *ref_lock;
 378
 379         read_cache();
 380         if (checkout_fast_forward(from, to))
 381                 exit(1); /* the callee should have complained already */
 382         ref_lock = lock_any_ref_for_update("HEAD", from, 0);
 383         return write_ref_sha1(ref_lock, to, "cherry-pick");
 384 }
 385
 386 static int do_recursive_merge(struct commit *base, struct commit *next,
 387                               const char *base_label, const char *next_label,
 388                               unsigned char *head, struct strbuf *msgbuf,
 389                               struct replay_opts *opts)
 390 {
 391         struct merge_options o;
 392         struct tree *result, *next_tree, *base_tree, *head_tree;
 393         int clean, index_fd;
 394         const char **xopt;
 395         static struct lock_file index_lock;
 396
 397         index_fd = hold_locked_index(&index_lock, 1);
 398
 399         read_cache();
 400
 401         init_merge_options(&o);
 402         o.ancestor = base ? base_label : "(empty tree)";
 403         o.branch1 = "HEAD";
 404         o.branch2 = next ? next_label : "(empty tree)";
 405
 406         head_tree = parse_tree_indirect(head);
 407         next_tree = next ? next->tree : empty_tree();
 408         base_tree = base ? base->tree : empty_tree();
 409
 410         for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
 411                 parse_merge_opt(&o, *xopt);
 412
 413         clean = merge_trees(&o,
 414                             head_tree,
 415                             next_tree, base_tree, &result);
 416
 417         if (active_cache_changed &&
 418             (write_cache(index_fd, active_cache, active_nr) ||
 419              commit_locked_index(&index_lock)))
 420                 /* TRANSLATORS: %s will be "revert" or "cherry-pick" */
 421                 die(_("%s: Unable to write new index file"), action_name(opts));
 422         rollback_lock_file(&index_lock);
 423
 424         if (!clean) {
 425                 int i;
 426                 strbuf_addstr(msgbuf, "\nConflicts:\n\n");
 427                 for (i = 0; i < active_nr;) {
 428                         struct cache_entry *ce = active_cache[i++];
 429                         if (ce_stage(ce)) {
 430                                 strbuf_addch(msgbuf, '\t');
 431                                 strbuf_addstr(msgbuf, ce->name);
 432                                 strbuf_addch(msgbuf, '\n');
 433                                 while (i < active_nr && !strcmp(ce->name,
 434                                                 active_cache[i]->name))
 435                                         i++;
 436                         }
 437                 }
 438         }
 439
 440         return !clean;
 441 }
 442
 443 /*
 444  * If we are cherry-pick, and if the merge did not result in
 445  * hand-editing, we will hit this commit and inherit the original
 446  * author date and name.
 447  * If we are revert, or if our cherry-pick results in a hand merge,
 448  * we had better say that the current user is responsible for that.
 449  */
 450 static int run_git_commit(const char *defmsg, struct replay_opts *opts)
 451 {
 452         /* 6 is max possible length of our args array including NULL */
 453         const char *args[6];
 454         int i = 0;
 455
 456         args[i++] = "commit";
 457         args[i++] = "-n";
 458         if (opts->signoff)
 459                 args[i++] = "-s";
 460         if (!opts->edit) {
 461                 args[i++] = "-F";
 462                 args[i++] = defmsg;
 463         }
 464         args[i] = NULL;
 465
 466         return run_command_v_opt(args, RUN_GIT_CMD);
 467 }
 468
 469 static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 470 {
 471         unsigned char head[20];
 472         struct commit *base, *next, *parent;
 473         const char *base_label, *next_label;
 474         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 475         char *defmsg = NULL;
 476         struct strbuf msgbuf = STRBUF_INIT;
 477         int res;
 478
 479         if (opts->no_commit) {
 480                 /*
 481                  * We do not intend to commit immediately.  We just want to
 482                  * merge the differences in, so let's compute the tree
 483                  * that represents the "current" state for merge-recursive
 484                  * to work on.
 485                  */
 486                 if (write_cache_as_tree(head, 0, NULL))
 487                         die (_("Your index file is unmerged."));
 488         } else {
 489                 if (get_sha1("HEAD", head))
 490                         return error(_("You do not have a valid HEAD"));
 491                 if (index_differs_from("HEAD", 0))
 492                         return error_dirty_index(opts);
 493         }
 494         discard_cache();
 495
 496         if (!commit->parents) {
 497                 parent = NULL;
 498         }
 499         else if (commit->parents->next) {
 500                 /* Reverting or cherry-picking a merge commit */
 501                 int cnt;
 502                 struct commit_list *p;
 503
 504                 if (!opts->mainline)
 505                         return error(_("Commit %s is a merge but no -m option was given."),
 506                                 sha1_to_hex(commit->object.sha1));
 507
 508                 for (cnt = 1, p = commit->parents;
 509                      cnt != opts->mainline && p;
 510                      cnt++)
 511                         p = p->next;
 512                 if (cnt != opts->mainline || !p)
 513                         return error(_("Commit %s does not have parent %d"),
 514                                 sha1_to_hex(commit->object.sha1), opts->mainline);
 515                 parent = p->item;
 516         } else if (0 < opts->mainline)
 517                 return error(_("Mainline was specified but commit %s is not a merge."),
 518                         sha1_to_hex(commit->object.sha1));
 519         else
 520                 parent = commit->parents->item;
 521
 522         if (opts->allow_ff && parent && !hashcmp(parent->object.sha1, head))
 523                 return fast_forward_to(commit->object.sha1, head);
 524
 525         if (parent && parse_commit(parent) < 0)
 526                 /* TRANSLATORS: The first %s will be "revert" or
 527                    "cherry-pick", the second %s a SHA1 */
 528                 return error(_("%s: cannot parse parent commit %s"),
 529                         action_name(opts), sha1_to_hex(parent->object.sha1));
 530
 531         if (get_message(commit, &msg) != 0)
 532                 return error(_("Cannot get commit message for %s"),
 533                         sha1_to_hex(commit->object.sha1));
 534
 535         /*
 536          * "commit" is an existing commit.  We would want to apply
 537          * the difference it introduces since its first parent "prev"
 538          * on top of the current HEAD if we are cherry-pick.  Or the
 539          * reverse of it if we are revert.
 540          */
 541
 542         defmsg = git_pathdup("MERGE_MSG");
 543
 544         if (opts->action == REVERT) {
 545                 base = commit;
 546                 base_label = msg.label;
 547                 next = parent;
 548                 next_label = msg.parent_label;
 549                 strbuf_addstr(&msgbuf, "Revert \"");
 550                 strbuf_addstr(&msgbuf, msg.subject);
 551                 strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
 552                 strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 553
 554                 if (commit->parents && commit->parents->next) {
 555                         strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
 556                         strbuf_addstr(&msgbuf, sha1_to_hex(parent->object.sha1));
 557                 }
 558                 strbuf_addstr(&msgbuf, ".\n");
 559         } else {
 560                 const char *p;
 561
 562                 base = parent;
 563                 base_label = msg.parent_label;
 564                 next = commit;
 565                 next_label = msg.label;
 566
 567                 /*
 568                  * Append the commit log message to msgbuf; it starts
 569                  * after the tree, parent, author, committer
 570                  * information followed by "\n\n".
 571                  */
 572                 p = strstr(msg.message, "\n\n");
 573                 if (p) {
 574                         p += 2;
 575                         strbuf_addstr(&msgbuf, p);
 576                 }
 577
 578                 if (opts->record_origin) {
 579                         strbuf_addstr(&msgbuf, "(cherry picked from commit ");
 580                         strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 581                         strbuf_addstr(&msgbuf, ")\n");
 582                 }
 583         }
 584
 585         if (!opts->strategy || !strcmp(opts->strategy, "recursive") || opts->action == REVERT) {
 586                 res = do_recursive_merge(base, next, base_label, next_label,
 587                                          head, &msgbuf, opts);
 588                 write_message(&msgbuf, defmsg);
 589         } else {
 590                 struct commit_list *common = NULL;
 591                 struct commit_list *remotes = NULL;
 592
 593                 write_message(&msgbuf, defmsg);
 594
 595                 commit_list_insert(base, &common);
 596                 commit_list_insert(next, &remotes);
 597                 res = try_merge_command(opts->strategy, opts->xopts_nr, opts->xopts,
 598                                         common, sha1_to_hex(head), remotes);
 599                 free_commit_list(common);
 600                 free_commit_list(remotes);
 601         }
 602
 603         /*
 604          * If the merge was clean or if it failed due to conflict, we write
 605          * CHERRY_PICK_HEAD for the subsequent invocation of commit to use.
 606          * However, if the merge did not even start, then we don't want to
 607          * write it at all.
 608          */
 609         if (opts->action == CHERRY_PICK && !opts->no_commit && (res == 0 || res == 1))
 610                 write_cherry_pick_head(commit, "CHERRY_PICK_HEAD");
 611         if (opts->action == REVERT && ((opts->no_commit && res == 0) || res == 1))
 612                 write_cherry_pick_head(commit, "REVERT_HEAD");
 613
 614         if (res) {
 615                 error(opts->action == REVERT
 616                       ? _("could not revert %s... %s")
 617                       : _("could not apply %s... %s"),
 618                       find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV),
 619                       msg.subject);
 620                 print_advice(res == 1);
 621                 rerere(opts->allow_rerere_auto);
 622         } else {
 623                 if (!opts->no_commit)
 624                         res = run_git_commit(defmsg, opts);
 625         }
 626
 627         free_message(&msg);
 628         free(defmsg);
 629
 630         return res;
 631 }
 632
 633 static void prepare_revs(struct rev_info *revs, struct replay_opts *opts)
 634 {
 635         int argc;
 636
 637         init_revisions(revs, NULL);
 638         revs->no_walk = 1;
 639         if (opts->action != REVERT)
 640                 revs->reverse = 1;
 641
 642         argc = setup_revisions(opts->commit_argc, opts->commit_argv, revs, NULL);
 643         if (argc > 1)
 644                 usage(*revert_or_cherry_pick_usage(opts));
 645
 646         if (prepare_revision_walk(revs))
 647                 die(_("revision walk setup failed"));
 648
 649         if (!revs->commits)
 650                 die(_("empty commit set passed"));
 651 }
 652
 653 static void read_and_refresh_cache(struct replay_opts *opts)
 654 {
 655         static struct lock_file index_lock;
 656         int index_fd = hold_locked_index(&index_lock, 0);
 657         if (read_index_preload(&the_index, NULL) < 0)
 658                 die(_("git %s: failed to read the index"), action_name(opts));
 659         refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
 660         if (the_index.cache_changed) {
 661                 if (write_index(&the_index, index_fd) ||
 662                     commit_locked_index(&index_lock))
 663                         die(_("git %s: failed to refresh the index"), action_name(opts));
 664         }
 665         rollback_lock_file(&index_lock);
 666 }
 667
 668 /*
 669  * Append a commit to the end of the commit_list.
 670  *
 671  * next starts by pointing to the variable that holds the head of an
 672  * empty commit_list, and is updated to point to the "next" field of
 673  * the last item on the list as new commits are appended.
 674  *
 675  * Usage example:
 676  *
 677  *     struct commit_list *list;
 678  *     struct commit_list **next = &list;
 679  *
 680  *     next = commit_list_append(c1, next);
 681  *     next = commit_list_append(c2, next);
 682  *     assert(commit_list_count(list) == 2);
 683  *     return list;
 684  */
 685 static struct commit_list **commit_list_append(struct commit *commit,
 686                                                struct commit_list **next)
 687 {
 688         struct commit_list *new = xmalloc(sizeof(struct commit_list));
 689         new->item = commit;
 690         *next = new;
 691         new->next = NULL;
 692         return &new->next;
 693 }
 694
 695 static int format_todo(struct strbuf *buf, struct commit_list *todo_list,
 696                 struct replay_opts *opts)
 697 {
 698         struct commit_list *cur = NULL;
 699         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 700         const char *sha1_abbrev = NULL;
 701         const char *action_str = opts->action == REVERT ? "revert" : "pick";
 702
 703         for (cur = todo_list; cur; cur = cur->next) {
 704                 sha1_abbrev = find_unique_abbrev(cur->item->object.sha1, DEFAULT_ABBREV);
 705                 if (get_message(cur->item, &msg))
 706                         return error(_("Cannot get commit message for %s"), sha1_abbrev);
 707                 strbuf_addf(buf, "%s %s %s\n", action_str, sha1_abbrev, msg.subject);
 708         }
 709         return 0;
 710 }
 711
 712 static struct commit *parse_insn_line(char *start, struct replay_opts *opts)
 713 {
 714         unsigned char commit_sha1[20];
 715         char sha1_abbrev[40];
 716         enum replay_action action;
 717         int insn_len = 0;
 718         char *p, *q;
 719
 720         if (!prefixcmp(start, "pick ")) {
 721                 action = CHERRY_PICK;
 722                 insn_len = strlen("pick");
 723                 p = start + insn_len + 1;
 724         } else if (!prefixcmp(start, "revert ")) {
 725                 action = REVERT;
 726                 insn_len = strlen("revert");
 727                 p = start + insn_len + 1;
 728         } else
 729                 return NULL;
 730
 731         q = strchr(p, ' ');
 732         if (!q)
 733                 return NULL;
 734         q++;
 735
 736         strlcpy(sha1_abbrev, p, q - p);
 737
 738         /*
 739          * Verify that the action matches up with the one in
 740          * opts; we don't support arbitrary instructions
 741          */
 742         if (action != opts->action) {
 743                 const char *action_str;
 744                 action_str = action == REVERT ? "revert" : "cherry-pick";
 745                 error(_("Cannot %s during a %s"), action_str, action_name(opts));
 746                 return NULL;
 747         }
 748
 749         if (get_sha1(sha1_abbrev, commit_sha1) < 0)
 750                 return NULL;
 751
 752         return lookup_commit_reference(commit_sha1);
 753 }
 754
 755 static int parse_insn_buffer(char *buf, struct commit_list **todo_list,
 756                         struct replay_opts *opts)
 757 {
 758         struct commit_list **next = todo_list;
 759         struct commit *commit;
 760         char *p = buf;
 761         int i;
 762
 763         for (i = 1; *p; i++) {
 764                 commit = parse_insn_line(p, opts);
 765                 if (!commit)
 766                         return error(_("Could not parse line %d."), i);
 767                 next = commit_list_append(commit, next);
 768                 p = strchrnul(p, '\n');
 769                 if (*p)
 770                         p++;
 771         }
 772         if (!*todo_list)
 773                 return error(_("No commits parsed."));
 774         return 0;
 775 }
 776
 777 static void read_populate_todo(struct commit_list **todo_list,
 778                         struct replay_opts *opts)
 779 {
 780         const char *todo_file = git_path(SEQ_TODO_FILE);
 781         struct strbuf buf = STRBUF_INIT;
 782         int fd, res;
 783
 784         fd = open(todo_file, O_RDONLY);
 785         if (fd < 0)
 786                 die_errno(_("Could not open %s"), todo_file);
 787         if (strbuf_read(&buf, fd, 0) < 0) {
 788                 close(fd);
 789                 strbuf_release(&buf);
 790                 die(_("Could not read %s."), todo_file);
 791         }
 792         close(fd);
 793
 794         res = parse_insn_buffer(buf.buf, todo_list, opts);
 795         strbuf_release(&buf);
 796         if (res)
 797                 die(_("Unusable instruction sheet: %s"), todo_file);
 798 }
 799
 800 static int populate_opts_cb(const char *key, const char *value, void *data)
 801 {
 802         struct replay_opts *opts = data;
 803         int error_flag = 1;
 804
 805         if (!value)
 806                 error_flag = 0;
 807         else if (!strcmp(key, "options.no-commit"))
 808                 opts->no_commit = git_config_bool_or_int(key, value, &error_flag);
 809         else if (!strcmp(key, "options.edit"))
 810                 opts->edit = git_config_bool_or_int(key, value, &error_flag);
 811         else if (!strcmp(key, "options.signoff"))
 812                 opts->signoff = git_config_bool_or_int(key, value, &error_flag);
 813         else if (!strcmp(key, "options.record-origin"))
 814                 opts->record_origin = git_config_bool_or_int(key, value, &error_flag);
 815         else if (!strcmp(key, "options.allow-ff"))
 816                 opts->allow_ff = git_config_bool_or_int(key, value, &error_flag);
 817         else if (!strcmp(key, "options.mainline"))
 818                 opts->mainline = git_config_int(key, value);
 819         else if (!strcmp(key, "options.strategy"))
 820                 git_config_string(&opts->strategy, key, value);
 821         else if (!strcmp(key, "options.strategy-option")) {
 822                 ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
 823                 opts->xopts[opts->xopts_nr++] = xstrdup(value);
 824         } else
 825                 return error(_("Invalid key: %s"), key);
 826
 827         if (!error_flag)
 828                 return error(_("Invalid value for %s: %s"), key, value);
 829
 830         return 0;
 831 }
 832
 833 static void read_populate_opts(struct replay_opts **opts_ptr)
 834 {
 835         const char *opts_file = git_path(SEQ_OPTS_FILE);
 836
 837         if (!file_exists(opts_file))
 838                 return;
 839         if (git_config_from_file(populate_opts_cb, opts_file, *opts_ptr) < 0)
 840                 die(_("Malformed options sheet: %s"), opts_file);
 841 }
 842
 843 static void walk_revs_populate_todo(struct commit_list **todo_list,
 844                                 struct replay_opts *opts)
 845 {
 846         struct rev_info revs;
 847         struct commit *commit;
 848         struct commit_list **next;
 849
 850         prepare_revs(&revs, opts);
 851
 852         next = todo_list;
 853         while ((commit = get_revision(&revs)))
 854                 next = commit_list_append(commit, next);
 855 }
 856
 857 static int create_seq_dir(void)
 858 {
 859         const char *seq_dir = git_path(SEQ_DIR);
 860
 861         if (file_exists(seq_dir)) {
 862                 error(_("a cherry-pick or revert is already in progress"));
 863                 advise(_("try \"git cherry-pick (--continue | --quit | --abort)\""));
 864                 return -1;
 865         }
 866         else if (mkdir(seq_dir, 0777) < 0)
 867                 die_errno(_("Could not create sequencer directory %s"), seq_dir);
 868         return 0;
 869 }
 870
 871 static void save_head(const char *head)
 872 {
 873         const char *head_file = git_path(SEQ_HEAD_FILE);
 874         static struct lock_file head_lock;
 875         struct strbuf buf = STRBUF_INIT;
 876         int fd;
 877
 878         fd = hold_lock_file_for_update(&head_lock, head_file, LOCK_DIE_ON_ERROR);
 879         strbuf_addf(&buf, "%s\n", head);
 880         if (write_in_full(fd, buf.buf, buf.len) < 0)
 881                 die_errno(_("Could not write to %s"), head_file);
 882         if (commit_lock_file(&head_lock) < 0)
 883                 die(_("Error wrapping up %s."), head_file);
 884 }
 885
 886 static int reset_for_rollback(const unsigned char *sha1)
 887 {
 888         const char *argv[4];    /* reset --merge <arg> + NULL */
 889         argv[0] = "reset";
 890         argv[1] = "--merge";
 891         argv[2] = sha1_to_hex(sha1);
 892         argv[3] = NULL;
 893         return run_command_v_opt(argv, RUN_GIT_CMD);
 894 }
 895
 896 static int rollback_single_pick(void)
 897 {
 898         unsigned char head_sha1[20];
 899
 900         if (!file_exists(git_path("CHERRY_PICK_HEAD")) &&
 901             !file_exists(git_path("REVERT_HEAD")))
 902                 return error(_("no cherry-pick or revert in progress"));
 903         if (!resolve_ref("HEAD", head_sha1, 0, NULL))
 904                 return error(_("cannot resolve HEAD"));
 905         if (is_null_sha1(head_sha1))
 906                 return error(_("cannot abort from a branch yet to be born"));
 907         return reset_for_rollback(head_sha1);
 908 }
 909
 910 static int sequencer_rollback(struct replay_opts *opts)
 911 {
 912         const char *filename;
 913         FILE *f;
 914         unsigned char sha1[20];
 915         struct strbuf buf = STRBUF_INIT;
 916
 917         filename = git_path(SEQ_HEAD_FILE);
 918         f = fopen(filename, "r");
 919         if (!f && errno == ENOENT) {
 920                 /*
 921                  * There is no multiple-cherry-pick in progress.
 922                  * If CHERRY_PICK_HEAD or REVERT_HEAD indicates
 923                  * a single-cherry-pick in progress, abort that.
 924                  */
 925                 return rollback_single_pick();
 926         }
 927         if (!f)
 928                 return error(_("cannot open %s: %s"), filename,
 929                                                 strerror(errno));
 930         if (strbuf_getline(&buf, f, '\n')) {
 931                 error(_("cannot read %s: %s"), filename, ferror(f) ?
 932                         strerror(errno) : _("unexpected end of file"));
 933                 fclose(f);
 934                 goto fail;
 935         }
 936         fclose(f);
 937         if (get_sha1_hex(buf.buf, sha1) || buf.buf[40] != '\0') {
 938                 error(_("stored pre-cherry-pick HEAD file '%s' is corrupt"),
 939                         filename);
 940                 goto fail;
 941         }
 942         if (reset_for_rollback(sha1))
 943                 goto fail;
 944         remove_sequencer_state(1);
 945         strbuf_release(&buf);
 946         return 0;
 947 fail:
 948         strbuf_release(&buf);
 949         return -1;
 950 }
 951
 952 static void save_todo(struct commit_list *todo_list, struct replay_opts *opts)
 953 {
 954         const char *todo_file = git_path(SEQ_TODO_FILE);
 955         static struct lock_file todo_lock;
 956         struct strbuf buf = STRBUF_INIT;
 957         int fd;
 958
 959         fd = hold_lock_file_for_update(&todo_lock, todo_file, LOCK_DIE_ON_ERROR);
 960         if (format_todo(&buf, todo_list, opts) < 0)
 961                 die(_("Could not format %s."), todo_file);
 962         if (write_in_full(fd, buf.buf, buf.len) < 0) {
 963                 strbuf_release(&buf);
 964                 die_errno(_("Could not write to %s"), todo_file);
 965         }
 966         if (commit_lock_file(&todo_lock) < 0) {
 967                 strbuf_release(&buf);
 968                 die(_("Error wrapping up %s."), todo_file);
 969         }
 970         strbuf_release(&buf);
 971 }
 972
 973 static void save_opts(struct replay_opts *opts)
 974 {
 975         const char *opts_file = git_path(SEQ_OPTS_FILE);
 976
 977         if (opts->no_commit)
 978                 git_config_set_in_file(opts_file, "options.no-commit", "true");
 979         if (opts->edit)
 980                 git_config_set_in_file(opts_file, "options.edit", "true");
 981         if (opts->signoff)
 982                 git_config_set_in_file(opts_file, "options.signoff", "true");
 983         if (opts->record_origin)
 984                 git_config_set_in_file(opts_file, "options.record-origin", "true");
 985         if (opts->allow_ff)
 986                 git_config_set_in_file(opts_file, "options.allow-ff", "true");
 987         if (opts->mainline) {
 988                 struct strbuf buf = STRBUF_INIT;
 989                 strbuf_addf(&buf, "%d", opts->mainline);
 990                 git_config_set_in_file(opts_file, "options.mainline", buf.buf);
 991                 strbuf_release(&buf);
 992         }
 993         if (opts->strategy)
 994                 git_config_set_in_file(opts_file, "options.strategy", opts->strategy);
 995         if (opts->xopts) {
 996                 int i;
 997                 for (i = 0; i < opts->xopts_nr; i++)
 998                         git_config_set_multivar_in_file(opts_file,
 999                                                         "options.strategy-option",
1000                                                         opts->xopts[i], "^$", 0);
1001         }
1002 }
1003
1004 static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
1005 {
1006         struct commit_list *cur;
1007         int res;
1008
1009         setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
1010         if (opts->allow_ff)
1011                 assert(!(opts->signoff || opts->no_commit ||
1012                                 opts->record_origin || opts->edit));
1013         read_and_refresh_cache(opts);
1014
1015         for (cur = todo_list; cur; cur = cur->next) {
1016                 save_todo(cur, opts);
1017                 res = do_pick_commit(cur->item, opts);
1018                 if (res) {
1019                         if (!cur->next)
1020                                 /*
1021                                  * An error was encountered while
1022                                  * picking the last commit; the
1023                                  * sequencer state is useless now --
1024                                  * the user simply needs to resolve
1025                                  * the conflict and commit
1026                                  */
1027                                 remove_sequencer_state(0);
1028                         return res;
1029                 }
1030         }
1031
1032         /*
1033          * Sequence of picks finished successfully; cleanup by
1034          * removing the .git/sequencer directory
1035          */
1036         remove_sequencer_state(1);
1037         return 0;
1038 }
1039
1040 static int pick_revisions(struct replay_opts *opts)
1041 {
1042         struct commit_list *todo_list = NULL;
1043         unsigned char sha1[20];
1044
1045         read_and_refresh_cache(opts);
1046
1047         /*
1048          * Decide what to do depending on the arguments; a fresh
1049          * cherry-pick should be handled differently from an existing
1050          * one that is being continued
1051          */
1052         if (opts->subcommand == REPLAY_REMOVE_STATE) {
1053                 remove_sequencer_state(1);
1054                 return 0;
1055         }
1056         if (opts->subcommand == REPLAY_ROLLBACK)
1057                 return sequencer_rollback(opts);
1058         if (opts->subcommand == REPLAY_CONTINUE) {
1059                 if (!file_exists(git_path(SEQ_TODO_FILE)))
1060                         return error(_("No %s in progress"), action_name(opts));
1061                 read_populate_opts(&opts);
1062                 read_populate_todo(&todo_list, opts);
1063
1064                 /* Verify that the conflict has been resolved */
1065                 if (!index_differs_from("HEAD", 0))
1066                         todo_list = todo_list->next;
1067                 return pick_commits(todo_list, opts);
1068         }
1069
1070         /*
1071          * Start a new cherry-pick/ revert sequence; but
1072          * first, make sure that an existing one isn't in
1073          * progress
1074          */
1075
1076         walk_revs_populate_todo(&todo_list, opts);
1077         if (create_seq_dir() < 0)
1078                 return -1;
1079         if (get_sha1("HEAD", sha1)) {
1080                 if (opts->action == REVERT)
1081                         return error(_("Can't revert as initial commit"));
1082                 return error(_("Can't cherry-pick into empty head"));
1083         }
1084         save_head(sha1_to_hex(sha1));
1085         save_opts(opts);
1086         return pick_commits(todo_list, opts);
1087 }
1088
1089 int cmd_revert(int argc, const char **argv, const char *prefix)
1090 {
1091         struct replay_opts opts;
1092         int res;
1093
1094         memset(&opts, 0, sizeof(opts));
1095         if (isatty(0))
1096                 opts.edit = 1;
1097         opts.action = REVERT;
1098         git_config(git_default_config, NULL);
1099         parse_args(argc, argv, &opts);
1100         res = pick_revisions(&opts);
1101         if (res < 0)
1102                 die(_("revert failed"));
1103         return res;
1104 }
1105
1106 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
1107 {
1108         struct replay_opts opts;
1109         int res;
1110
1111         memset(&opts, 0, sizeof(opts));
1112         opts.action = CHERRY_PICK;
1113         git_config(git_default_config, NULL);
1114         parse_args(argc, argv, &opts);
1115         res = pick_revisions(&opts);
1116         if (res < 0)
1117                 die(_("cherry-pick failed"));
1118         return res;
1119 }