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");
 337                 advise("with 'git add <paths>' or 'git rm <paths>'");
 338                 advise("and commit the result with 'git commit'");
 339         }
 340 }
 341
 342 static void write_message(struct strbuf *msgbuf, const char *filename)
 343 {
 344         static struct lock_file msg_file;
 345
 346         int msg_fd = hold_lock_file_for_update(&msg_file, filename,
 347                                                LOCK_DIE_ON_ERROR);
 348         if (write_in_full(msg_fd, msgbuf->buf, msgbuf->len) < 0)
 349                 die_errno(_("Could not write to %s"), filename);
 350         strbuf_release(msgbuf);
 351         if (commit_lock_file(&msg_file) < 0)
 352                 die(_("Error wrapping up %s"), filename);
 353 }
 354
 355 static struct tree *empty_tree(void)
 356 {
 357         return lookup_tree((const unsigned char *)EMPTY_TREE_SHA1_BIN);
 358 }
 359
 360 static int error_dirty_index(struct replay_opts *opts)
 361 {
 362         if (read_cache_unmerged())
 363                 return error_resolve_conflict(action_name(opts));
 364
 365         /* Different translation strings for cherry-pick and revert */
 366         if (opts->action == CHERRY_PICK)
 367                 error(_("Your local changes would be overwritten by cherry-pick."));
 368         else
 369                 error(_("Your local changes would be overwritten by revert."));
 370
 371         if (advice_commit_before_merge)
 372                 advise(_("Commit your changes or stash them to proceed."));
 373         return -1;
 374 }
 375
 376 static int fast_forward_to(const unsigned char *to, const unsigned char *from)
 377 {
 378         struct ref_lock *ref_lock;
 379
 380         read_cache();
 381         if (checkout_fast_forward(from, to))
 382                 exit(1); /* the callee should have complained already */
 383         ref_lock = lock_any_ref_for_update("HEAD", from, 0);
 384         return write_ref_sha1(ref_lock, to, "cherry-pick");
 385 }
 386
 387 static int do_recursive_merge(struct commit *base, struct commit *next,
 388                               const char *base_label, const char *next_label,
 389                               unsigned char *head, struct strbuf *msgbuf,
 390                               struct replay_opts *opts)
 391 {
 392         struct merge_options o;
 393         struct tree *result, *next_tree, *base_tree, *head_tree;
 394         int clean, index_fd;
 395         const char **xopt;
 396         static struct lock_file index_lock;
 397
 398         index_fd = hold_locked_index(&index_lock, 1);
 399
 400         read_cache();
 401
 402         init_merge_options(&o);
 403         o.ancestor = base ? base_label : "(empty tree)";
 404         o.branch1 = "HEAD";
 405         o.branch2 = next ? next_label : "(empty tree)";
 406
 407         head_tree = parse_tree_indirect(head);
 408         next_tree = next ? next->tree : empty_tree();
 409         base_tree = base ? base->tree : empty_tree();
 410
 411         for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
 412                 parse_merge_opt(&o, *xopt);
 413
 414         clean = merge_trees(&o,
 415                             head_tree,
 416                             next_tree, base_tree, &result);
 417
 418         if (active_cache_changed &&
 419             (write_cache(index_fd, active_cache, active_nr) ||
 420              commit_locked_index(&index_lock)))
 421                 /* TRANSLATORS: %s will be "revert" or "cherry-pick" */
 422                 die(_("%s: Unable to write new index file"), action_name(opts));
 423         rollback_lock_file(&index_lock);
 424
 425         if (!clean) {
 426                 int i;
 427                 strbuf_addstr(msgbuf, "\nConflicts:\n\n");
 428                 for (i = 0; i < active_nr;) {
 429                         struct cache_entry *ce = active_cache[i++];
 430                         if (ce_stage(ce)) {
 431                                 strbuf_addch(msgbuf, '\t');
 432                                 strbuf_addstr(msgbuf, ce->name);
 433                                 strbuf_addch(msgbuf, '\n');
 434                                 while (i < active_nr && !strcmp(ce->name,
 435                                                 active_cache[i]->name))
 436                                         i++;
 437                         }
 438                 }
 439         }
 440
 441         return !clean;
 442 }
 443
 444 /*
 445  * If we are cherry-pick, and if the merge did not result in
 446  * hand-editing, we will hit this commit and inherit the original
 447  * author date and name.
 448  * If we are revert, or if our cherry-pick results in a hand merge,
 449  * we had better say that the current user is responsible for that.
 450  */
 451 static int run_git_commit(const char *defmsg, struct replay_opts *opts)
 452 {
 453         /* 6 is max possible length of our args array including NULL */
 454         const char *args[6];
 455         int i = 0;
 456
 457         args[i++] = "commit";
 458         args[i++] = "-n";
 459         if (opts->signoff)
 460                 args[i++] = "-s";
 461         if (!opts->edit) {
 462                 args[i++] = "-F";
 463                 args[i++] = defmsg;
 464         }
 465         args[i] = NULL;
 466
 467         return run_command_v_opt(args, RUN_GIT_CMD);
 468 }
 469
 470 static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 471 {
 472         unsigned char head[20];
 473         struct commit *base, *next, *parent;
 474         const char *base_label, *next_label;
 475         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 476         char *defmsg = NULL;
 477         struct strbuf msgbuf = STRBUF_INIT;
 478         int res;
 479
 480         if (opts->no_commit) {
 481                 /*
 482                  * We do not intend to commit immediately.  We just want to
 483                  * merge the differences in, so let's compute the tree
 484                  * that represents the "current" state for merge-recursive
 485                  * to work on.
 486                  */
 487                 if (write_cache_as_tree(head, 0, NULL))
 488                         die (_("Your index file is unmerged."));
 489         } else {
 490                 if (get_sha1("HEAD", head))
 491                         return error(_("You do not have a valid HEAD"));
 492                 if (index_differs_from("HEAD", 0))
 493                         return error_dirty_index(opts);
 494         }
 495         discard_cache();
 496
 497         if (!commit->parents) {
 498                 parent = NULL;
 499         }
 500         else if (commit->parents->next) {
 501                 /* Reverting or cherry-picking a merge commit */
 502                 int cnt;
 503                 struct commit_list *p;
 504
 505                 if (!opts->mainline)
 506                         return error(_("Commit %s is a merge but no -m option was given."),
 507                                 sha1_to_hex(commit->object.sha1));
 508
 509                 for (cnt = 1, p = commit->parents;
 510                      cnt != opts->mainline && p;
 511                      cnt++)
 512                         p = p->next;
 513                 if (cnt != opts->mainline || !p)
 514                         return error(_("Commit %s does not have parent %d"),
 515                                 sha1_to_hex(commit->object.sha1), opts->mainline);
 516                 parent = p->item;
 517         } else if (0 < opts->mainline)
 518                 return error(_("Mainline was specified but commit %s is not a merge."),
 519                         sha1_to_hex(commit->object.sha1));
 520         else
 521                 parent = commit->parents->item;
 522
 523         if (opts->allow_ff && parent && !hashcmp(parent->object.sha1, head))
 524                 return fast_forward_to(commit->object.sha1, head);
 525
 526         if (parent && parse_commit(parent) < 0)
 527                 /* TRANSLATORS: The first %s will be "revert" or
 528                    "cherry-pick", the second %s a SHA1 */
 529                 return error(_("%s: cannot parse parent commit %s"),
 530                         action_name(opts), sha1_to_hex(parent->object.sha1));
 531
 532         if (get_message(commit, &msg) != 0)
 533                 return error(_("Cannot get commit message for %s"),
 534                         sha1_to_hex(commit->object.sha1));
 535
 536         /*
 537          * "commit" is an existing commit.  We would want to apply
 538          * the difference it introduces since its first parent "prev"
 539          * on top of the current HEAD if we are cherry-pick.  Or the
 540          * reverse of it if we are revert.
 541          */
 542
 543         defmsg = git_pathdup("MERGE_MSG");
 544
 545         if (opts->action == REVERT) {
 546                 base = commit;
 547                 base_label = msg.label;
 548                 next = parent;
 549                 next_label = msg.parent_label;
 550                 strbuf_addstr(&msgbuf, "Revert \"");
 551                 strbuf_addstr(&msgbuf, msg.subject);
 552                 strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
 553                 strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 554
 555                 if (commit->parents && commit->parents->next) {
 556                         strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
 557                         strbuf_addstr(&msgbuf, sha1_to_hex(parent->object.sha1));
 558                 }
 559                 strbuf_addstr(&msgbuf, ".\n");
 560         } else {
 561                 const char *p;
 562
 563                 base = parent;
 564                 base_label = msg.parent_label;
 565                 next = commit;
 566                 next_label = msg.label;
 567
 568                 /*
 569                  * Append the commit log message to msgbuf; it starts
 570                  * after the tree, parent, author, committer
 571                  * information followed by "\n\n".
 572                  */
 573                 p = strstr(msg.message, "\n\n");
 574                 if (p) {
 575                         p += 2;
 576                         strbuf_addstr(&msgbuf, p);
 577                 }
 578
 579                 if (opts->record_origin) {
 580                         strbuf_addstr(&msgbuf, "(cherry picked from commit ");
 581                         strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 582                         strbuf_addstr(&msgbuf, ")\n");
 583                 }
 584         }
 585
 586         if (!opts->strategy || !strcmp(opts->strategy, "recursive") || opts->action == REVERT) {
 587                 res = do_recursive_merge(base, next, base_label, next_label,
 588                                          head, &msgbuf, opts);
 589                 write_message(&msgbuf, defmsg);
 590         } else {
 591                 struct commit_list *common = NULL;
 592                 struct commit_list *remotes = NULL;
 593
 594                 write_message(&msgbuf, defmsg);
 595
 596                 commit_list_insert(base, &common);
 597                 commit_list_insert(next, &remotes);
 598                 res = try_merge_command(opts->strategy, opts->xopts_nr, opts->xopts,
 599                                         common, sha1_to_hex(head), remotes);
 600                 free_commit_list(common);
 601                 free_commit_list(remotes);
 602         }
 603
 604         /*
 605          * If the merge was clean or if it failed due to conflict, we write
 606          * CHERRY_PICK_HEAD for the subsequent invocation of commit to use.
 607          * However, if the merge did not even start, then we don't want to
 608          * write it at all.
 609          */
 610         if (opts->action == CHERRY_PICK && !opts->no_commit && (res == 0 || res == 1))
 611                 write_cherry_pick_head(commit, "CHERRY_PICK_HEAD");
 612         if (opts->action == REVERT && ((opts->no_commit && res == 0) || res == 1))
 613                 write_cherry_pick_head(commit, "REVERT_HEAD");
 614
 615         if (res) {
 616                 error(opts->action == REVERT
 617                       ? _("could not revert %s... %s")
 618                       : _("could not apply %s... %s"),
 619                       find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV),
 620                       msg.subject);
 621                 print_advice(res == 1);
 622                 rerere(opts->allow_rerere_auto);
 623         } else {
 624                 if (!opts->no_commit)
 625                         res = run_git_commit(defmsg, opts);
 626         }
 627
 628         free_message(&msg);
 629         free(defmsg);
 630
 631         return res;
 632 }
 633
 634 static void prepare_revs(struct rev_info *revs, struct replay_opts *opts)
 635 {
 636         int argc;
 637
 638         init_revisions(revs, NULL);
 639         revs->no_walk = 1;
 640         if (opts->action != REVERT)
 641                 revs->reverse = 1;
 642
 643         argc = setup_revisions(opts->commit_argc, opts->commit_argv, revs, NULL);
 644         if (argc > 1)
 645                 usage(*revert_or_cherry_pick_usage(opts));
 646
 647         if (prepare_revision_walk(revs))
 648                 die(_("revision walk setup failed"));
 649
 650         if (!revs->commits)
 651                 die(_("empty commit set passed"));
 652 }
 653
 654 static void read_and_refresh_cache(struct replay_opts *opts)
 655 {
 656         static struct lock_file index_lock;
 657         int index_fd = hold_locked_index(&index_lock, 0);
 658         if (read_index_preload(&the_index, NULL) < 0)
 659                 die(_("git %s: failed to read the index"), action_name(opts));
 660         refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
 661         if (the_index.cache_changed) {
 662                 if (write_index(&the_index, index_fd) ||
 663                     commit_locked_index(&index_lock))
 664                         die(_("git %s: failed to refresh the index"), action_name(opts));
 665         }
 666         rollback_lock_file(&index_lock);
 667 }
 668
 669 /*
 670  * Append a commit to the end of the commit_list.
 671  *
 672  * next starts by pointing to the variable that holds the head of an
 673  * empty commit_list, and is updated to point to the "next" field of
 674  * the last item on the list as new commits are appended.
 675  *
 676  * Usage example:
 677  *
 678  *     struct commit_list *list;
 679  *     struct commit_list **next = &list;
 680  *
 681  *     next = commit_list_append(c1, next);
 682  *     next = commit_list_append(c2, next);
 683  *     assert(commit_list_count(list) == 2);
 684  *     return list;
 685  */
 686 static struct commit_list **commit_list_append(struct commit *commit,
 687                                                struct commit_list **next)
 688 {
 689         struct commit_list *new = xmalloc(sizeof(struct commit_list));
 690         new->item = commit;
 691         *next = new;
 692         new->next = NULL;
 693         return &new->next;
 694 }
 695
 696 static int format_todo(struct strbuf *buf, struct commit_list *todo_list,
 697                 struct replay_opts *opts)
 698 {
 699         struct commit_list *cur = NULL;
 700         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 701         const char *sha1_abbrev = NULL;
 702         const char *action_str = opts->action == REVERT ? "revert" : "pick";
 703
 704         for (cur = todo_list; cur; cur = cur->next) {
 705                 sha1_abbrev = find_unique_abbrev(cur->item->object.sha1, DEFAULT_ABBREV);
 706                 if (get_message(cur->item, &msg))
 707                         return error(_("Cannot get commit message for %s"), sha1_abbrev);
 708                 strbuf_addf(buf, "%s %s %s\n", action_str, sha1_abbrev, msg.subject);
 709         }
 710         return 0;
 711 }
 712
 713 static struct commit *parse_insn_line(char *start, struct replay_opts *opts)
 714 {
 715         unsigned char commit_sha1[20];
 716         char sha1_abbrev[40];
 717         enum replay_action action;
 718         int insn_len = 0;
 719         char *p, *q;
 720
 721         if (!prefixcmp(start, "pick ")) {
 722                 action = CHERRY_PICK;
 723                 insn_len = strlen("pick");
 724                 p = start + insn_len + 1;
 725         } else if (!prefixcmp(start, "revert ")) {
 726                 action = REVERT;
 727                 insn_len = strlen("revert");
 728                 p = start + insn_len + 1;
 729         } else
 730                 return NULL;
 731
 732         q = strchr(p, ' ');
 733         if (!q)
 734                 return NULL;
 735         q++;
 736
 737         strlcpy(sha1_abbrev, p, q - p);
 738
 739         /*
 740          * Verify that the action matches up with the one in
 741          * opts; we don't support arbitrary instructions
 742          */
 743         if (action != opts->action) {
 744                 const char *action_str;
 745                 action_str = action == REVERT ? "revert" : "cherry-pick";
 746                 error(_("Cannot %s during a %s"), action_str, action_name(opts));
 747                 return NULL;
 748         }
 749
 750         if (get_sha1(sha1_abbrev, commit_sha1) < 0)
 751                 return NULL;
 752
 753         return lookup_commit_reference(commit_sha1);
 754 }
 755
 756 static int parse_insn_buffer(char *buf, struct commit_list **todo_list,
 757                         struct replay_opts *opts)
 758 {
 759         struct commit_list **next = todo_list;
 760         struct commit *commit;
 761         char *p = buf;
 762         int i;
 763
 764         for (i = 1; *p; i++) {
 765                 commit = parse_insn_line(p, opts);
 766                 if (!commit)
 767                         return error(_("Could not parse line %d."), i);
 768                 next = commit_list_append(commit, next);
 769                 p = strchrnul(p, '\n');
 770                 if (*p)
 771                         p++;
 772         }
 773         if (!*todo_list)
 774                 return error(_("No commits parsed."));
 775         return 0;
 776 }
 777
 778 static void read_populate_todo(struct commit_list **todo_list,
 779                         struct replay_opts *opts)
 780 {
 781         const char *todo_file = git_path(SEQ_TODO_FILE);
 782         struct strbuf buf = STRBUF_INIT;
 783         int fd, res;
 784
 785         fd = open(todo_file, O_RDONLY);
 786         if (fd < 0)
 787                 die_errno(_("Could not open %s"), todo_file);
 788         if (strbuf_read(&buf, fd, 0) < 0) {
 789                 close(fd);
 790                 strbuf_release(&buf);
 791                 die(_("Could not read %s."), todo_file);
 792         }
 793         close(fd);
 794
 795         res = parse_insn_buffer(buf.buf, todo_list, opts);
 796         strbuf_release(&buf);
 797         if (res)
 798                 die(_("Unusable instruction sheet: %s"), todo_file);
 799 }
 800
 801 static int populate_opts_cb(const char *key, const char *value, void *data)
 802 {
 803         struct replay_opts *opts = data;
 804         int error_flag = 1;
 805
 806         if (!value)
 807                 error_flag = 0;
 808         else if (!strcmp(key, "options.no-commit"))
 809                 opts->no_commit = git_config_bool_or_int(key, value, &error_flag);
 810         else if (!strcmp(key, "options.edit"))
 811                 opts->edit = git_config_bool_or_int(key, value, &error_flag);
 812         else if (!strcmp(key, "options.signoff"))
 813                 opts->signoff = git_config_bool_or_int(key, value, &error_flag);
 814         else if (!strcmp(key, "options.record-origin"))
 815                 opts->record_origin = git_config_bool_or_int(key, value, &error_flag);
 816         else if (!strcmp(key, "options.allow-ff"))
 817                 opts->allow_ff = git_config_bool_or_int(key, value, &error_flag);
 818         else if (!strcmp(key, "options.mainline"))
 819                 opts->mainline = git_config_int(key, value);
 820         else if (!strcmp(key, "options.strategy"))
 821                 git_config_string(&opts->strategy, key, value);
 822         else if (!strcmp(key, "options.strategy-option")) {
 823                 ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
 824                 opts->xopts[opts->xopts_nr++] = xstrdup(value);
 825         } else
 826                 return error(_("Invalid key: %s"), key);
 827
 828         if (!error_flag)
 829                 return error(_("Invalid value for %s: %s"), key, value);
 830
 831         return 0;
 832 }
 833
 834 static void read_populate_opts(struct replay_opts **opts_ptr)
 835 {
 836         const char *opts_file = git_path(SEQ_OPTS_FILE);
 837
 838         if (!file_exists(opts_file))
 839                 return;
 840         if (git_config_from_file(populate_opts_cb, opts_file, *opts_ptr) < 0)
 841                 die(_("Malformed options sheet: %s"), opts_file);
 842 }
 843
 844 static void walk_revs_populate_todo(struct commit_list **todo_list,
 845                                 struct replay_opts *opts)
 846 {
 847         struct rev_info revs;
 848         struct commit *commit;
 849         struct commit_list **next;
 850
 851         prepare_revs(&revs, opts);
 852
 853         next = todo_list;
 854         while ((commit = get_revision(&revs)))
 855                 next = commit_list_append(commit, next);
 856 }
 857
 858 static int create_seq_dir(void)
 859 {
 860         const char *seq_dir = git_path(SEQ_DIR);
 861
 862         if (file_exists(seq_dir)) {
 863                 error(_("a cherry-pick or revert is already in progress"));
 864                 advise(_("try \"git cherry-pick (--continue | --quit | --abort)\""));
 865                 return -1;
 866         }
 867         else if (mkdir(seq_dir, 0777) < 0)
 868                 die_errno(_("Could not create sequencer directory %s"), seq_dir);
 869         return 0;
 870 }
 871
 872 static void save_head(const char *head)
 873 {
 874         const char *head_file = git_path(SEQ_HEAD_FILE);
 875         static struct lock_file head_lock;
 876         struct strbuf buf = STRBUF_INIT;
 877         int fd;
 878
 879         fd = hold_lock_file_for_update(&head_lock, head_file, LOCK_DIE_ON_ERROR);
 880         strbuf_addf(&buf, "%s\n", head);
 881         if (write_in_full(fd, buf.buf, buf.len) < 0)
 882                 die_errno(_("Could not write to %s"), head_file);
 883         if (commit_lock_file(&head_lock) < 0)
 884                 die(_("Error wrapping up %s."), head_file);
 885 }
 886
 887 static int reset_for_rollback(const unsigned char *sha1)
 888 {
 889         const char *argv[4];    /* reset --merge <arg> + NULL */
 890         argv[0] = "reset";
 891         argv[1] = "--merge";
 892         argv[2] = sha1_to_hex(sha1);
 893         argv[3] = NULL;
 894         return run_command_v_opt(argv, RUN_GIT_CMD);
 895 }
 896
 897 static int rollback_single_pick(void)
 898 {
 899         unsigned char head_sha1[20];
 900
 901         if (!file_exists(git_path("CHERRY_PICK_HEAD")) &&
 902             !file_exists(git_path("REVERT_HEAD")))
 903                 return error(_("no cherry-pick or revert in progress"));
 904         if (read_ref_full("HEAD", head_sha1, 0, NULL))
 905                 return error(_("cannot resolve HEAD"));
 906         if (is_null_sha1(head_sha1))
 907                 return error(_("cannot abort from a branch yet to be born"));
 908         return reset_for_rollback(head_sha1);
 909 }
 910
 911 static int sequencer_rollback(struct replay_opts *opts)
 912 {
 913         const char *filename;
 914         FILE *f;
 915         unsigned char sha1[20];
 916         struct strbuf buf = STRBUF_INIT;
 917
 918         filename = git_path(SEQ_HEAD_FILE);
 919         f = fopen(filename, "r");
 920         if (!f && errno == ENOENT) {
 921                 /*
 922                  * There is no multiple-cherry-pick in progress.
 923                  * If CHERRY_PICK_HEAD or REVERT_HEAD indicates
 924                  * a single-cherry-pick in progress, abort that.
 925                  */
 926                 return rollback_single_pick();
 927         }
 928         if (!f)
 929                 return error(_("cannot open %s: %s"), filename,
 930                                                 strerror(errno));
 931         if (strbuf_getline(&buf, f, '\n')) {
 932                 error(_("cannot read %s: %s"), filename, ferror(f) ?
 933                         strerror(errno) : _("unexpected end of file"));
 934                 fclose(f);
 935                 goto fail;
 936         }
 937         fclose(f);
 938         if (get_sha1_hex(buf.buf, sha1) || buf.buf[40] != '\0') {
 939                 error(_("stored pre-cherry-pick HEAD file '%s' is corrupt"),
 940                         filename);
 941                 goto fail;
 942         }
 943         if (reset_for_rollback(sha1))
 944                 goto fail;
 945         remove_sequencer_state(1);
 946         strbuf_release(&buf);
 947         return 0;
 948 fail:
 949         strbuf_release(&buf);
 950         return -1;
 951 }
 952
 953 static void save_todo(struct commit_list *todo_list, struct replay_opts *opts)
 954 {
 955         const char *todo_file = git_path(SEQ_TODO_FILE);
 956         static struct lock_file todo_lock;
 957         struct strbuf buf = STRBUF_INIT;
 958         int fd;
 959
 960         fd = hold_lock_file_for_update(&todo_lock, todo_file, LOCK_DIE_ON_ERROR);
 961         if (format_todo(&buf, todo_list, opts) < 0)
 962                 die(_("Could not format %s."), todo_file);
 963         if (write_in_full(fd, buf.buf, buf.len) < 0) {
 964                 strbuf_release(&buf);
 965                 die_errno(_("Could not write to %s"), todo_file);
 966         }
 967         if (commit_lock_file(&todo_lock) < 0) {
 968                 strbuf_release(&buf);
 969                 die(_("Error wrapping up %s."), todo_file);
 970         }
 971         strbuf_release(&buf);
 972 }
 973
 974 static void save_opts(struct replay_opts *opts)
 975 {
 976         const char *opts_file = git_path(SEQ_OPTS_FILE);
 977
 978         if (opts->no_commit)
 979                 git_config_set_in_file(opts_file, "options.no-commit", "true");
 980         if (opts->edit)
 981                 git_config_set_in_file(opts_file, "options.edit", "true");
 982         if (opts->signoff)
 983                 git_config_set_in_file(opts_file, "options.signoff", "true");
 984         if (opts->record_origin)
 985                 git_config_set_in_file(opts_file, "options.record-origin", "true");
 986         if (opts->allow_ff)
 987                 git_config_set_in_file(opts_file, "options.allow-ff", "true");
 988         if (opts->mainline) {
 989                 struct strbuf buf = STRBUF_INIT;
 990                 strbuf_addf(&buf, "%d", opts->mainline);
 991                 git_config_set_in_file(opts_file, "options.mainline", buf.buf);
 992                 strbuf_release(&buf);
 993         }
 994         if (opts->strategy)
 995                 git_config_set_in_file(opts_file, "options.strategy", opts->strategy);
 996         if (opts->xopts) {
 997                 int i;
 998                 for (i = 0; i < opts->xopts_nr; i++)
 999                         git_config_set_multivar_in_file(opts_file,
1000                                                         "options.strategy-option",
1001                                                         opts->xopts[i], "^$", 0);
1002         }
1003 }
1004
1005 static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
1006 {
1007         struct commit_list *cur;
1008         int res;
1009
1010         setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
1011         if (opts->allow_ff)
1012                 assert(!(opts->signoff || opts->no_commit ||
1013                                 opts->record_origin || opts->edit));
1014         read_and_refresh_cache(opts);
1015
1016         for (cur = todo_list; cur; cur = cur->next) {
1017                 save_todo(cur, opts);
1018                 res = do_pick_commit(cur->item, opts);
1019                 if (res) {
1020                         if (!cur->next)
1021                                 /*
1022                                  * An error was encountered while
1023                                  * picking the last commit; the
1024                                  * sequencer state is useless now --
1025                                  * the user simply needs to resolve
1026                                  * the conflict and commit
1027                                  */
1028                                 remove_sequencer_state(0);
1029                         return res;
1030                 }
1031         }
1032
1033         /*
1034          * Sequence of picks finished successfully; cleanup by
1035          * removing the .git/sequencer directory
1036          */
1037         remove_sequencer_state(1);
1038         return 0;
1039 }
1040
1041 static int pick_revisions(struct replay_opts *opts)
1042 {
1043         struct commit_list *todo_list = NULL;
1044         unsigned char sha1[20];
1045
1046         read_and_refresh_cache(opts);
1047
1048         /*
1049          * Decide what to do depending on the arguments; a fresh
1050          * cherry-pick should be handled differently from an existing
1051          * one that is being continued
1052          */
1053         if (opts->subcommand == REPLAY_REMOVE_STATE) {
1054                 remove_sequencer_state(1);
1055                 return 0;
1056         }
1057         if (opts->subcommand == REPLAY_ROLLBACK)
1058                 return sequencer_rollback(opts);
1059         if (opts->subcommand == REPLAY_CONTINUE) {
1060                 if (!file_exists(git_path(SEQ_TODO_FILE)))
1061                         return error(_("No %s in progress"), action_name(opts));
1062                 read_populate_opts(&opts);
1063                 read_populate_todo(&todo_list, opts);
1064
1065                 /* Verify that the conflict has been resolved */
1066                 if (!index_differs_from("HEAD", 0))
1067                         todo_list = todo_list->next;
1068                 return pick_commits(todo_list, opts);
1069         }
1070
1071         /*
1072          * Start a new cherry-pick/ revert sequence; but
1073          * first, make sure that an existing one isn't in
1074          * progress
1075          */
1076
1077         walk_revs_populate_todo(&todo_list, opts);
1078         if (create_seq_dir() < 0)
1079                 return -1;
1080         if (get_sha1("HEAD", sha1)) {
1081                 if (opts->action == REVERT)
1082                         return error(_("Can't revert as initial commit"));
1083                 return error(_("Can't cherry-pick into empty head"));
1084         }
1085         save_head(sha1_to_hex(sha1));
1086         save_opts(opts);
1087         return pick_commits(todo_list, opts);
1088 }
1089
1090 int cmd_revert(int argc, const char **argv, const char *prefix)
1091 {
1092         struct replay_opts opts;
1093         int res;
1094
1095         memset(&opts, 0, sizeof(opts));
1096         if (isatty(0))
1097                 opts.edit = 1;
1098         opts.action = REVERT;
1099         git_config(git_default_config, NULL);
1100         parse_args(argc, argv, &opts);
1101         res = pick_revisions(&opts);
1102         if (res < 0)
1103                 die(_("revert failed"));
1104         return res;
1105 }
1106
1107 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
1108 {
1109         struct replay_opts opts;
1110         int res;
1111
1112         memset(&opts, 0, sizeof(opts));
1113         opts.action = CHERRY_PICK;
1114         git_config(git_default_config, NULL);
1115         parse_args(argc, argv, &opts);
1116         res = pick_revisions(&opts);
1117         if (res < 0)
1118                 die(_("cherry-pick failed"));
1119         return res;
1120 }