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