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 { REPLAY_NONE, REPLAY_RESET };
  44
  45 struct replay_opts {
  46         enum replay_action action;
  47         enum replay_subcommand subcommand;
  48
  49         /* Boolean options */
  50         int edit;
  51         int record_origin;
  52         int no_commit;
  53         int signoff;
  54         int allow_ff;
  55         int allow_rerere_auto;
  56
  57         int mainline;
  58         int commit_argc;
  59         const char **commit_argv;
  60
  61         /* Merge strategy */
  62         const char *strategy;
  63         const char **xopts;
  64         size_t xopts_nr, xopts_alloc;
  65 };
  66
  67 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
  68
  69 static const char *action_name(const struct replay_opts *opts)
  70 {
  71         return opts->action == REVERT ? "revert" : "cherry-pick";
  72 }
  73
  74 static char *get_encoding(const char *message);
  75
  76 static const char * const *revert_or_cherry_pick_usage(struct replay_opts *opts)
  77 {
  78         return opts->action == REVERT ? revert_usage : cherry_pick_usage;
  79 }
  80
  81 static int option_parse_x(const struct option *opt,
  82                           const char *arg, int unset)
  83 {
  84         struct replay_opts **opts_ptr = opt->value;
  85         struct replay_opts *opts = *opts_ptr;
  86
  87         if (unset)
  88                 return 0;
  89
  90         ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
  91         opts->xopts[opts->xopts_nr++] = xstrdup(arg);
  92         return 0;
  93 }
  94
  95 static void verify_opt_compatible(const char *me, const char *base_opt, ...)
  96 {
  97         const char *this_opt;
  98         va_list ap;
  99
 100         va_start(ap, base_opt);
 101         while ((this_opt = va_arg(ap, const char *))) {
 102                 if (va_arg(ap, int))
 103                         break;
 104         }
 105         va_end(ap);
 106
 107         if (this_opt)
 108                 die(_("%s: %s cannot be used with %s"), me, this_opt, base_opt);
 109 }
 110
 111 static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 112 {
 113         const char * const * usage_str = revert_or_cherry_pick_usage(opts);
 114         const char *me = action_name(opts);
 115         int noop;
 116         int reset = 0;
 117         struct option options[] = {
 118                 OPT_BOOLEAN(0, "reset", &reset, "forget the current operation"),
 119                 OPT_BOOLEAN('n', "no-commit", &opts->no_commit, "don't automatically commit"),
 120                 OPT_BOOLEAN('e', "edit", &opts->edit, "edit the commit message"),
 121                 { OPTION_BOOLEAN, 'r', NULL, &noop, NULL, "no-op (backward compatibility)",
 122                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN, NULL, 0 },
 123                 OPT_BOOLEAN('s', "signoff", &opts->signoff, "add Signed-off-by:"),
 124                 OPT_INTEGER('m', "mainline", &opts->mainline, "parent number"),
 125                 OPT_RERERE_AUTOUPDATE(&opts->allow_rerere_auto),
 126                 OPT_STRING(0, "strategy", &opts->strategy, "strategy", "merge strategy"),
 127                 OPT_CALLBACK('X', "strategy-option", &opts, "option",
 128                         "option for merge strategy", option_parse_x),
 129                 OPT_END(),
 130                 OPT_END(),
 131                 OPT_END(),
 132         };
 133
 134         if (opts->action == CHERRY_PICK) {
 135                 struct option cp_extra[] = {
 136                         OPT_BOOLEAN('x', NULL, &opts->record_origin, "append commit name"),
 137                         OPT_BOOLEAN(0, "ff", &opts->allow_ff, "allow fast-forward"),
 138                         OPT_END(),
 139                 };
 140                 if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))
 141                         die(_("program error"));
 142         }
 143
 144         opts->commit_argc = parse_options(argc, argv, NULL, options, usage_str,
 145                                         PARSE_OPT_KEEP_ARGV0 |
 146                                         PARSE_OPT_KEEP_UNKNOWN);
 147
 148         /* Set the subcommand */
 149         if (reset)
 150                 opts->subcommand = REPLAY_RESET;
 151         else
 152                 opts->subcommand = REPLAY_NONE;
 153
 154         /* Check for incompatible command line arguments */
 155         if (opts->subcommand == REPLAY_RESET) {
 156                 verify_opt_compatible(me, "--reset",
 157                                 "--no-commit", opts->no_commit,
 158                                 "--signoff", opts->signoff,
 159                                 "--mainline", opts->mainline,
 160                                 "--strategy", opts->strategy ? 1 : 0,
 161                                 "--strategy-option", opts->xopts ? 1 : 0,
 162                                 "-x", opts->record_origin,
 163                                 "--ff", opts->allow_ff,
 164                                 NULL);
 165         }
 166
 167         else if (opts->commit_argc < 2)
 168                 usage_with_options(usage_str, options);
 169
 170         if (opts->allow_ff)
 171                 verify_opt_compatible(me, "--ff",
 172                                 "--signoff", opts->signoff,
 173                                 "--no-commit", opts->no_commit,
 174                                 "-x", opts->record_origin,
 175                                 "--edit", opts->edit,
 176                                 NULL);
 177         opts->commit_argv = argv;
 178 }
 179
 180 struct commit_message {
 181         char *parent_label;
 182         const char *label;
 183         const char *subject;
 184         char *reencoded_message;
 185         const char *message;
 186 };
 187
 188 static int get_message(struct commit *commit, struct commit_message *out)
 189 {
 190         const char *encoding;
 191         const char *abbrev, *subject;
 192         int abbrev_len, subject_len;
 193         char *q;
 194
 195         if (!commit->buffer)
 196                 return -1;
 197         encoding = get_encoding(commit->buffer);
 198         if (!encoding)
 199                 encoding = "UTF-8";
 200         if (!git_commit_encoding)
 201                 git_commit_encoding = "UTF-8";
 202
 203         out->reencoded_message = NULL;
 204         out->message = commit->buffer;
 205         if (strcmp(encoding, git_commit_encoding))
 206                 out->reencoded_message = reencode_string(commit->buffer,
 207                                         git_commit_encoding, encoding);
 208         if (out->reencoded_message)
 209                 out->message = out->reencoded_message;
 210
 211         abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
 212         abbrev_len = strlen(abbrev);
 213
 214         subject_len = find_commit_subject(out->message, &subject);
 215
 216         out->parent_label = xmalloc(strlen("parent of ") + abbrev_len +
 217                               strlen("... ") + subject_len + 1);
 218         q = out->parent_label;
 219         q = mempcpy(q, "parent of ", strlen("parent of "));
 220         out->label = q;
 221         q = mempcpy(q, abbrev, abbrev_len);
 222         q = mempcpy(q, "... ", strlen("... "));
 223         out->subject = q;
 224         q = mempcpy(q, subject, subject_len);
 225         *q = '\0';
 226         return 0;
 227 }
 228
 229 static void free_message(struct commit_message *msg)
 230 {
 231         free(msg->parent_label);
 232         free(msg->reencoded_message);
 233 }
 234
 235 static char *get_encoding(const char *message)
 236 {
 237         const char *p = message, *eol;
 238
 239         while (*p && *p != '\n') {
 240                 for (eol = p + 1; *eol && *eol != '\n'; eol++)
 241                         ; /* do nothing */
 242                 if (!prefixcmp(p, "encoding ")) {
 243                         char *result = xmalloc(eol - 8 - p);
 244                         strlcpy(result, p + 9, eol - 8 - p);
 245                         return result;
 246                 }
 247                 p = eol;
 248                 if (*p == '\n')
 249                         p++;
 250         }
 251         return NULL;
 252 }
 253
 254 static void write_cherry_pick_head(struct commit *commit)
 255 {
 256         int fd;
 257         struct strbuf buf = STRBUF_INIT;
 258
 259         strbuf_addf(&buf, "%s\n", sha1_to_hex(commit->object.sha1));
 260
 261         fd = open(git_path("CHERRY_PICK_HEAD"), O_WRONLY | O_CREAT, 0666);
 262         if (fd < 0)
 263                 die_errno(_("Could not open '%s' for writing"),
 264                           git_path("CHERRY_PICK_HEAD"));
 265         if (write_in_full(fd, buf.buf, buf.len) != buf.len || close(fd))
 266                 die_errno(_("Could not write to '%s'"), git_path("CHERRY_PICK_HEAD"));
 267         strbuf_release(&buf);
 268 }
 269
 270 static void print_advice(void)
 271 {
 272         char *msg = getenv("GIT_CHERRY_PICK_HELP");
 273
 274         if (msg) {
 275                 fprintf(stderr, "%s\n", msg);
 276                 /*
 277                  * A conflict has occured but the porcelain
 278                  * (typically rebase --interactive) wants to take care
 279                  * of the commit itself so remove CHERRY_PICK_HEAD
 280                  */
 281                 unlink(git_path("CHERRY_PICK_HEAD"));
 282                 return;
 283         }
 284
 285         advise("after resolving the conflicts, mark the corrected paths");
 286         advise("with 'git add <paths>' or 'git rm <paths>'");
 287         advise("and commit the result with 'git commit'");
 288 }
 289
 290 static void write_message(struct strbuf *msgbuf, const char *filename)
 291 {
 292         static struct lock_file msg_file;
 293
 294         int msg_fd = hold_lock_file_for_update(&msg_file, filename,
 295                                                LOCK_DIE_ON_ERROR);
 296         if (write_in_full(msg_fd, msgbuf->buf, msgbuf->len) < 0)
 297                 die_errno(_("Could not write to %s."), filename);
 298         strbuf_release(msgbuf);
 299         if (commit_lock_file(&msg_file) < 0)
 300                 die(_("Error wrapping up %s"), filename);
 301 }
 302
 303 static struct tree *empty_tree(void)
 304 {
 305         struct tree *tree = xcalloc(1, sizeof(struct tree));
 306
 307         tree->object.parsed = 1;
 308         tree->object.type = OBJ_TREE;
 309         pretend_sha1_file(NULL, 0, OBJ_TREE, tree->object.sha1);
 310         return tree;
 311 }
 312
 313 static NORETURN void die_dirty_index(struct replay_opts *opts)
 314 {
 315         if (read_cache_unmerged()) {
 316                 die_resolve_conflict(action_name(opts));
 317         } else {
 318                 if (advice_commit_before_merge) {
 319                         if (opts->action == REVERT)
 320                                 die(_("Your local changes would be overwritten by revert.\n"
 321                                           "Please, commit your changes or stash them to proceed."));
 322                         else
 323                                 die(_("Your local changes would be overwritten by cherry-pick.\n"
 324                                           "Please, commit your changes or stash them to proceed."));
 325                 } else {
 326                         if (opts->action == REVERT)
 327                                 die(_("Your local changes would be overwritten by revert.\n"));
 328                         else
 329                                 die(_("Your local changes would be overwritten by cherry-pick.\n"));
 330                 }
 331         }
 332 }
 333
 334 static int fast_forward_to(const unsigned char *to, const unsigned char *from)
 335 {
 336         struct ref_lock *ref_lock;
 337
 338         read_cache();
 339         if (checkout_fast_forward(from, to))
 340                 exit(1); /* the callee should have complained already */
 341         ref_lock = lock_any_ref_for_update("HEAD", from, 0);
 342         return write_ref_sha1(ref_lock, to, "cherry-pick");
 343 }
 344
 345 static int do_recursive_merge(struct commit *base, struct commit *next,
 346                               const char *base_label, const char *next_label,
 347                               unsigned char *head, struct strbuf *msgbuf,
 348                               struct replay_opts *opts)
 349 {
 350         struct merge_options o;
 351         struct tree *result, *next_tree, *base_tree, *head_tree;
 352         int clean, index_fd;
 353         const char **xopt;
 354         static struct lock_file index_lock;
 355
 356         index_fd = hold_locked_index(&index_lock, 1);
 357
 358         read_cache();
 359
 360         init_merge_options(&o);
 361         o.ancestor = base ? base_label : "(empty tree)";
 362         o.branch1 = "HEAD";
 363         o.branch2 = next ? next_label : "(empty tree)";
 364
 365         head_tree = parse_tree_indirect(head);
 366         next_tree = next ? next->tree : empty_tree();
 367         base_tree = base ? base->tree : empty_tree();
 368
 369         for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
 370                 parse_merge_opt(&o, *xopt);
 371
 372         clean = merge_trees(&o,
 373                             head_tree,
 374                             next_tree, base_tree, &result);
 375
 376         if (active_cache_changed &&
 377             (write_cache(index_fd, active_cache, active_nr) ||
 378              commit_locked_index(&index_lock)))
 379                 /* TRANSLATORS: %s will be "revert" or "cherry-pick" */
 380                 die(_("%s: Unable to write new index file"), action_name(opts));
 381         rollback_lock_file(&index_lock);
 382
 383         if (!clean) {
 384                 int i;
 385                 strbuf_addstr(msgbuf, "\nConflicts:\n\n");
 386                 for (i = 0; i < active_nr;) {
 387                         struct cache_entry *ce = active_cache[i++];
 388                         if (ce_stage(ce)) {
 389                                 strbuf_addch(msgbuf, '\t');
 390                                 strbuf_addstr(msgbuf, ce->name);
 391                                 strbuf_addch(msgbuf, '\n');
 392                                 while (i < active_nr && !strcmp(ce->name,
 393                                                 active_cache[i]->name))
 394                                         i++;
 395                         }
 396                 }
 397         }
 398
 399         return !clean;
 400 }
 401
 402 /*
 403  * If we are cherry-pick, and if the merge did not result in
 404  * hand-editing, we will hit this commit and inherit the original
 405  * author date and name.
 406  * If we are revert, or if our cherry-pick results in a hand merge,
 407  * we had better say that the current user is responsible for that.
 408  */
 409 static int run_git_commit(const char *defmsg, struct replay_opts *opts)
 410 {
 411         /* 6 is max possible length of our args array including NULL */
 412         const char *args[6];
 413         int i = 0;
 414
 415         args[i++] = "commit";
 416         args[i++] = "-n";
 417         if (opts->signoff)
 418                 args[i++] = "-s";
 419         if (!opts->edit) {
 420                 args[i++] = "-F";
 421                 args[i++] = defmsg;
 422         }
 423         args[i] = NULL;
 424
 425         return run_command_v_opt(args, RUN_GIT_CMD);
 426 }
 427
 428 static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 429 {
 430         unsigned char head[20];
 431         struct commit *base, *next, *parent;
 432         const char *base_label, *next_label;
 433         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 434         char *defmsg = NULL;
 435         struct strbuf msgbuf = STRBUF_INIT;
 436         int res;
 437
 438         if (opts->no_commit) {
 439                 /*
 440                  * We do not intend to commit immediately.  We just want to
 441                  * merge the differences in, so let's compute the tree
 442                  * that represents the "current" state for merge-recursive
 443                  * to work on.
 444                  */
 445                 if (write_cache_as_tree(head, 0, NULL))
 446                         die (_("Your index file is unmerged."));
 447         } else {
 448                 if (get_sha1("HEAD", head))
 449                         die (_("You do not have a valid HEAD"));
 450                 if (index_differs_from("HEAD", 0))
 451                         die_dirty_index(opts);
 452         }
 453         discard_cache();
 454
 455         if (!commit->parents) {
 456                 parent = NULL;
 457         }
 458         else if (commit->parents->next) {
 459                 /* Reverting or cherry-picking a merge commit */
 460                 int cnt;
 461                 struct commit_list *p;
 462
 463                 if (!opts->mainline)
 464                         die(_("Commit %s is a merge but no -m option was given."),
 465                             sha1_to_hex(commit->object.sha1));
 466
 467                 for (cnt = 1, p = commit->parents;
 468                      cnt != opts->mainline && p;
 469                      cnt++)
 470                         p = p->next;
 471                 if (cnt != opts->mainline || !p)
 472                         die(_("Commit %s does not have parent %d"),
 473                             sha1_to_hex(commit->object.sha1), opts->mainline);
 474                 parent = p->item;
 475         } else if (0 < opts->mainline)
 476                 die(_("Mainline was specified but commit %s is not a merge."),
 477                     sha1_to_hex(commit->object.sha1));
 478         else
 479                 parent = commit->parents->item;
 480
 481         if (opts->allow_ff && parent && !hashcmp(parent->object.sha1, head))
 482                 return fast_forward_to(commit->object.sha1, head);
 483
 484         if (parent && parse_commit(parent) < 0)
 485                 /* TRANSLATORS: The first %s will be "revert" or
 486                    "cherry-pick", the second %s a SHA1 */
 487                 die(_("%s: cannot parse parent commit %s"),
 488                     action_name(opts), sha1_to_hex(parent->object.sha1));
 489
 490         if (get_message(commit, &msg) != 0)
 491                 die(_("Cannot get commit message for %s"),
 492                                 sha1_to_hex(commit->object.sha1));
 493
 494         /*
 495          * "commit" is an existing commit.  We would want to apply
 496          * the difference it introduces since its first parent "prev"
 497          * on top of the current HEAD if we are cherry-pick.  Or the
 498          * reverse of it if we are revert.
 499          */
 500
 501         defmsg = git_pathdup("MERGE_MSG");
 502
 503         if (opts->action == REVERT) {
 504                 base = commit;
 505                 base_label = msg.label;
 506                 next = parent;
 507                 next_label = msg.parent_label;
 508                 strbuf_addstr(&msgbuf, "Revert \"");
 509                 strbuf_addstr(&msgbuf, msg.subject);
 510                 strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
 511                 strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 512
 513                 if (commit->parents && commit->parents->next) {
 514                         strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
 515                         strbuf_addstr(&msgbuf, sha1_to_hex(parent->object.sha1));
 516                 }
 517                 strbuf_addstr(&msgbuf, ".\n");
 518         } else {
 519                 const char *p;
 520
 521                 base = parent;
 522                 base_label = msg.parent_label;
 523                 next = commit;
 524                 next_label = msg.label;
 525
 526                 /*
 527                  * Append the commit log message to msgbuf; it starts
 528                  * after the tree, parent, author, committer
 529                  * information followed by "\n\n".
 530                  */
 531                 p = strstr(msg.message, "\n\n");
 532                 if (p) {
 533                         p += 2;
 534                         strbuf_addstr(&msgbuf, p);
 535                 }
 536
 537                 if (opts->record_origin) {
 538                         strbuf_addstr(&msgbuf, "(cherry picked from commit ");
 539                         strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 540                         strbuf_addstr(&msgbuf, ")\n");
 541                 }
 542                 if (!opts->no_commit)
 543                         write_cherry_pick_head(commit);
 544         }
 545
 546         if (!opts->strategy || !strcmp(opts->strategy, "recursive") || opts->action == REVERT) {
 547                 res = do_recursive_merge(base, next, base_label, next_label,
 548                                          head, &msgbuf, opts);
 549                 write_message(&msgbuf, defmsg);
 550         } else {
 551                 struct commit_list *common = NULL;
 552                 struct commit_list *remotes = NULL;
 553
 554                 write_message(&msgbuf, defmsg);
 555
 556                 commit_list_insert(base, &common);
 557                 commit_list_insert(next, &remotes);
 558                 res = try_merge_command(opts->strategy, opts->xopts_nr, opts->xopts,
 559                                         common, sha1_to_hex(head), remotes);
 560                 free_commit_list(common);
 561                 free_commit_list(remotes);
 562         }
 563
 564         if (res) {
 565                 error(opts->action == REVERT
 566                       ? _("could not revert %s... %s")
 567                       : _("could not apply %s... %s"),
 568                       find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV),
 569                       msg.subject);
 570                 print_advice();
 571                 rerere(opts->allow_rerere_auto);
 572         } else {
 573                 if (!opts->no_commit)
 574                         res = run_git_commit(defmsg, opts);
 575         }
 576
 577         free_message(&msg);
 578         free(defmsg);
 579
 580         return res;
 581 }
 582
 583 static void prepare_revs(struct rev_info *revs, struct replay_opts *opts)
 584 {
 585         int argc;
 586
 587         init_revisions(revs, NULL);
 588         revs->no_walk = 1;
 589         if (opts->action != REVERT)
 590                 revs->reverse = 1;
 591
 592         argc = setup_revisions(opts->commit_argc, opts->commit_argv, revs, NULL);
 593         if (argc > 1)
 594                 usage(*revert_or_cherry_pick_usage(opts));
 595
 596         if (prepare_revision_walk(revs))
 597                 die(_("revision walk setup failed"));
 598
 599         if (!revs->commits)
 600                 die(_("empty commit set passed"));
 601 }
 602
 603 static void read_and_refresh_cache(struct replay_opts *opts)
 604 {
 605         static struct lock_file index_lock;
 606         int index_fd = hold_locked_index(&index_lock, 0);
 607         if (read_index_preload(&the_index, NULL) < 0)
 608                 die(_("git %s: failed to read the index"), action_name(opts));
 609         refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
 610         if (the_index.cache_changed) {
 611                 if (write_index(&the_index, index_fd) ||
 612                     commit_locked_index(&index_lock))
 613                         die(_("git %s: failed to refresh the index"), action_name(opts));
 614         }
 615         rollback_lock_file(&index_lock);
 616 }
 617
 618 /*
 619  * Append a commit to the end of the commit_list.
 620  *
 621  * next starts by pointing to the variable that holds the head of an
 622  * empty commit_list, and is updated to point to the "next" field of
 623  * the last item on the list as new commits are appended.
 624  *
 625  * Usage example:
 626  *
 627  *     struct commit_list *list;
 628  *     struct commit_list **next = &list;
 629  *
 630  *     next = commit_list_append(c1, next);
 631  *     next = commit_list_append(c2, next);
 632  *     assert(commit_list_count(list) == 2);
 633  *     return list;
 634  */
 635 struct commit_list **commit_list_append(struct commit *commit,
 636                                         struct commit_list **next)
 637 {
 638         struct commit_list *new = xmalloc(sizeof(struct commit_list));
 639         new->item = commit;
 640         *next = new;
 641         new->next = NULL;
 642         return &new->next;
 643 }
 644
 645 static int format_todo(struct strbuf *buf, struct commit_list *todo_list,
 646                 struct replay_opts *opts)
 647 {
 648         struct commit_list *cur = NULL;
 649         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 650         const char *sha1_abbrev = NULL;
 651         const char *action_str = opts->action == REVERT ? "revert" : "pick";
 652
 653         for (cur = todo_list; cur; cur = cur->next) {
 654                 sha1_abbrev = find_unique_abbrev(cur->item->object.sha1, DEFAULT_ABBREV);
 655                 if (get_message(cur->item, &msg))
 656                         return error(_("Cannot get commit message for %s"), sha1_abbrev);
 657                 strbuf_addf(buf, "%s %s %s\n", action_str, sha1_abbrev, msg.subject);
 658         }
 659         return 0;
 660 }
 661
 662 static void walk_revs_populate_todo(struct commit_list **todo_list,
 663                                 struct replay_opts *opts)
 664 {
 665         struct rev_info revs;
 666         struct commit *commit;
 667         struct commit_list **next;
 668
 669         prepare_revs(&revs, opts);
 670
 671         next = todo_list;
 672         while ((commit = get_revision(&revs)))
 673                 next = commit_list_append(commit, next);
 674 }
 675
 676 static void create_seq_dir(void)
 677 {
 678         const char *seq_dir = git_path(SEQ_DIR);
 679
 680         if (!(file_exists(seq_dir) && is_directory(seq_dir))
 681                 && mkdir(seq_dir, 0777) < 0)
 682                 die_errno(_("Could not create sequencer directory '%s'."), seq_dir);
 683 }
 684
 685 static void save_head(const char *head)
 686 {
 687         const char *head_file = git_path(SEQ_HEAD_FILE);
 688         static struct lock_file head_lock;
 689         struct strbuf buf = STRBUF_INIT;
 690         int fd;
 691
 692         fd = hold_lock_file_for_update(&head_lock, head_file, LOCK_DIE_ON_ERROR);
 693         strbuf_addf(&buf, "%s\n", head);
 694         if (write_in_full(fd, buf.buf, buf.len) < 0)
 695                 die_errno(_("Could not write to %s."), head_file);
 696         if (commit_lock_file(&head_lock) < 0)
 697                 die(_("Error wrapping up %s."), head_file);
 698 }
 699
 700 static void save_todo(struct commit_list *todo_list, struct replay_opts *opts)
 701 {
 702         const char *todo_file = git_path(SEQ_TODO_FILE);
 703         static struct lock_file todo_lock;
 704         struct strbuf buf = STRBUF_INIT;
 705         int fd;
 706
 707         fd = hold_lock_file_for_update(&todo_lock, todo_file, LOCK_DIE_ON_ERROR);
 708         if (format_todo(&buf, todo_list, opts) < 0)
 709                 die(_("Could not format %s."), todo_file);
 710         if (write_in_full(fd, buf.buf, buf.len) < 0) {
 711                 strbuf_release(&buf);
 712                 die_errno(_("Could not write to %s."), todo_file);
 713         }
 714         if (commit_lock_file(&todo_lock) < 0) {
 715                 strbuf_release(&buf);
 716                 die(_("Error wrapping up %s."), todo_file);
 717         }
 718         strbuf_release(&buf);
 719 }
 720
 721 static void save_opts(struct replay_opts *opts)
 722 {
 723         const char *opts_file = git_path(SEQ_OPTS_FILE);
 724
 725         if (opts->no_commit)
 726                 git_config_set_in_file(opts_file, "options.no-commit", "true");
 727         if (opts->edit)
 728                 git_config_set_in_file(opts_file, "options.edit", "true");
 729         if (opts->signoff)
 730                 git_config_set_in_file(opts_file, "options.signoff", "true");
 731         if (opts->record_origin)
 732                 git_config_set_in_file(opts_file, "options.record-origin", "true");
 733         if (opts->allow_ff)
 734                 git_config_set_in_file(opts_file, "options.allow-ff", "true");
 735         if (opts->mainline) {
 736                 struct strbuf buf = STRBUF_INIT;
 737                 strbuf_addf(&buf, "%d", opts->mainline);
 738                 git_config_set_in_file(opts_file, "options.mainline", buf.buf);
 739                 strbuf_release(&buf);
 740         }
 741         if (opts->strategy)
 742                 git_config_set_in_file(opts_file, "options.strategy", opts->strategy);
 743         if (opts->xopts) {
 744                 int i;
 745                 for (i = 0; i < opts->xopts_nr; i++)
 746                         git_config_set_multivar_in_file(opts_file,
 747                                                         "options.strategy-option",
 748                                                         opts->xopts[i], "^$", 0);
 749         }
 750 }
 751
 752 static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
 753 {
 754         struct commit_list *cur;
 755         int res;
 756
 757         setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
 758         if (opts->allow_ff)
 759                 assert(!(opts->signoff || opts->no_commit ||
 760                                 opts->record_origin || opts->edit));
 761         read_and_refresh_cache(opts);
 762
 763         for (cur = todo_list; cur; cur = cur->next) {
 764                 save_todo(cur, opts);
 765                 res = do_pick_commit(cur->item, opts);
 766                 if (res)
 767                         return res;
 768         }
 769
 770         /*
 771          * Sequence of picks finished successfully; cleanup by
 772          * removing the .git/sequencer directory
 773          */
 774         remove_sequencer_state(1);
 775         return 0;
 776 }
 777
 778 static int pick_revisions(struct replay_opts *opts)
 779 {
 780         struct commit_list *todo_list = NULL;
 781         unsigned char sha1[20];
 782
 783         read_and_refresh_cache(opts);
 784
 785         /*
 786          * Decide what to do depending on the arguments; a fresh
 787          * cherry-pick should be handled differently from an existing
 788          * one that is being continued
 789          */
 790         if (opts->subcommand == REPLAY_RESET) {
 791                 remove_sequencer_state(1);
 792                 return 0;
 793         } else {
 794                 /* Start a new cherry-pick/ revert sequence */
 795                 walk_revs_populate_todo(&todo_list, opts);
 796                 create_seq_dir();
 797                 if (get_sha1("HEAD", sha1)) {
 798                         if (opts->action == REVERT)
 799                                 die(_("Can't revert as initial commit"));
 800                         die(_("Can't cherry-pick into empty head"));
 801                 }
 802                 save_head(sha1_to_hex(sha1));
 803                 save_opts(opts);
 804         }
 805         return pick_commits(todo_list, opts);
 806 }
 807
 808 int cmd_revert(int argc, const char **argv, const char *prefix)
 809 {
 810         struct replay_opts opts;
 811
 812         memset(&opts, 0, sizeof(opts));
 813         if (isatty(0))
 814                 opts.edit = 1;
 815         opts.action = REVERT;
 816         git_config(git_default_config, NULL);
 817         parse_args(argc, argv, &opts);
 818         return pick_revisions(&opts);
 819 }
 820
 821 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 822 {
 823         struct replay_opts opts;
 824
 825         memset(&opts, 0, sizeof(opts));
 826         opts.action = CHERRY_PICK;
 827         git_config(git_default_config, NULL);
 828         parse_args(argc, argv, &opts);
 829         return pick_revisions(&opts);
 830 }