git.oblomov.eu Git - git/blob - 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, REPLAY_CONTINUE };
  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 verify_opt_mutually_compatible(const char *me, ...)
 112 {
 113         const char *opt1, *opt2;
 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 noop;
 137         int reset = 0;
 138         int contin = 0;
 139         struct option options[] = {
 140                 OPT_BOOLEAN(0, "reset", &reset, "forget the current operation"),
 141                 OPT_BOOLEAN(0, "continue", &contin, "continue the current operation"),
 142                 OPT_BOOLEAN('n', "no-commit", &opts->no_commit, "don't automatically commit"),
 143                 OPT_BOOLEAN('e', "edit", &opts->edit, "edit the commit message"),
 144                 { OPTION_BOOLEAN, 'r', NULL, &noop, NULL, "no-op (backward compatibility)",
 145                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN, NULL, 0 },
 146                 OPT_BOOLEAN('s', "signoff", &opts->signoff, "add Signed-off-by:"),
 147                 OPT_INTEGER('m', "mainline", &opts->mainline, "parent number"),
 148                 OPT_RERERE_AUTOUPDATE(&opts->allow_rerere_auto),
 149                 OPT_STRING(0, "strategy", &opts->strategy, "strategy", "merge strategy"),
 150                 OPT_CALLBACK('X', "strategy-option", &opts, "option",
 151                         "option for merge strategy", option_parse_x),
 152                 OPT_END(),
 153                 OPT_END(),
 154                 OPT_END(),
 155         };
 156
 157         if (opts->action == CHERRY_PICK) {
 158                 struct option cp_extra[] = {
 159                         OPT_BOOLEAN('x', NULL, &opts->record_origin, "append commit name"),
 160                         OPT_BOOLEAN(0, "ff", &opts->allow_ff, "allow fast-forward"),
 161                         OPT_END(),
 162                 };
 163                 if (parse_options_concat(options, ARRAY_SIZE(options), cp_extra))
 164                         die(_("program error"));
 165         }
 166
 167         opts->commit_argc = parse_options(argc, argv, NULL, options, usage_str,
 168                                         PARSE_OPT_KEEP_ARGV0 |
 169                                         PARSE_OPT_KEEP_UNKNOWN);
 170
 171         /* Check for incompatible subcommands */
 172         verify_opt_mutually_compatible(me,
 173                                 "--reset", reset,
 174                                 "--continue", contin,
 175                                 NULL);
 176
 177         /* Set the subcommand */
 178         if (reset)
 179                 opts->subcommand = REPLAY_RESET;
 180         else if (contin)
 181                 opts->subcommand = REPLAY_CONTINUE;
 182         else
 183                 opts->subcommand = REPLAY_NONE;
 184
 185         /* Check for incompatible command line arguments */
 186         if (opts->subcommand != REPLAY_NONE) {
 187                 char *this_operation;
 188                 if (opts->subcommand == REPLAY_RESET)
 189                         this_operation = "--reset";
 190                 else
 191                         this_operation = "--continue";
 192
 193                 verify_opt_compatible(me, this_operation,
 194                                 "--no-commit", opts->no_commit,
 195                                 "--signoff", opts->signoff,
 196                                 "--mainline", opts->mainline,
 197                                 "--strategy", opts->strategy ? 1 : 0,
 198                                 "--strategy-option", opts->xopts ? 1 : 0,
 199                                 "-x", opts->record_origin,
 200                                 "--ff", opts->allow_ff,
 201                                 NULL);
 202         }
 203
 204         else if (opts->commit_argc < 2)
 205                 usage_with_options(usage_str, options);
 206
 207         if (opts->allow_ff)
 208                 verify_opt_compatible(me, "--ff",
 209                                 "--signoff", opts->signoff,
 210                                 "--no-commit", opts->no_commit,
 211                                 "-x", opts->record_origin,
 212                                 "--edit", opts->edit,
 213                                 NULL);
 214         opts->commit_argv = argv;
 215 }
 216
 217 struct commit_message {
 218         char *parent_label;
 219         const char *label;
 220         const char *subject;
 221         char *reencoded_message;
 222         const char *message;
 223 };
 224
 225 static int get_message(struct commit *commit, struct commit_message *out)
 226 {
 227         const char *encoding;
 228         const char *abbrev, *subject;
 229         int abbrev_len, subject_len;
 230         char *q;
 231
 232         if (!commit->buffer)
 233                 return -1;
 234         encoding = get_encoding(commit->buffer);
 235         if (!encoding)
 236                 encoding = "UTF-8";
 237         if (!git_commit_encoding)
 238                 git_commit_encoding = "UTF-8";
 239
 240         out->reencoded_message = NULL;
 241         out->message = commit->buffer;
 242         if (strcmp(encoding, git_commit_encoding))
 243                 out->reencoded_message = reencode_string(commit->buffer,
 244                                         git_commit_encoding, encoding);
 245         if (out->reencoded_message)
 246                 out->message = out->reencoded_message;
 247
 248         abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
 249         abbrev_len = strlen(abbrev);
 250
 251         subject_len = find_commit_subject(out->message, &subject);
 252
 253         out->parent_label = xmalloc(strlen("parent of ") + abbrev_len +
 254                               strlen("... ") + subject_len + 1);
 255         q = out->parent_label;
 256         q = mempcpy(q, "parent of ", strlen("parent of "));
 257         out->label = q;
 258         q = mempcpy(q, abbrev, abbrev_len);
 259         q = mempcpy(q, "... ", strlen("... "));
 260         out->subject = q;
 261         q = mempcpy(q, subject, subject_len);
 262         *q = '\0';
 263         return 0;
 264 }
 265
 266 static void free_message(struct commit_message *msg)
 267 {
 268         free(msg->parent_label);
 269         free(msg->reencoded_message);
 270 }
 271
 272 static char *get_encoding(const char *message)
 273 {
 274         const char *p = message, *eol;
 275
 276         while (*p && *p != '\n') {
 277                 for (eol = p + 1; *eol && *eol != '\n'; eol++)
 278                         ; /* do nothing */
 279                 if (!prefixcmp(p, "encoding ")) {
 280                         char *result = xmalloc(eol - 8 - p);
 281                         strlcpy(result, p + 9, eol - 8 - p);
 282                         return result;
 283                 }
 284                 p = eol;
 285                 if (*p == '\n')
 286                         p++;
 287         }
 288         return NULL;
 289 }
 290
 291 static void write_cherry_pick_head(struct commit *commit)
 292 {
 293         int fd;
 294         struct strbuf buf = STRBUF_INIT;
 295
 296         strbuf_addf(&buf, "%s\n", sha1_to_hex(commit->object.sha1));
 297
 298         fd = open(git_path("CHERRY_PICK_HEAD"), O_WRONLY | O_CREAT, 0666);
 299         if (fd < 0)
 300                 die_errno(_("Could not open '%s' for writing"),
 301                           git_path("CHERRY_PICK_HEAD"));
 302         if (write_in_full(fd, buf.buf, buf.len) != buf.len || close(fd))
 303                 die_errno(_("Could not write to '%s'"), git_path("CHERRY_PICK_HEAD"));
 304         strbuf_release(&buf);
 305 }
 306
 307 static void print_advice(void)
 308 {
 309         char *msg = getenv("GIT_CHERRY_PICK_HELP");
 310
 311         if (msg) {
 312                 fprintf(stderr, "%s\n", msg);
 313                 /*
 314                  * A conflict has occured but the porcelain
 315                  * (typically rebase --interactive) wants to take care
 316                  * of the commit itself so remove CHERRY_PICK_HEAD
 317                  */
 318                 unlink(git_path("CHERRY_PICK_HEAD"));
 319                 return;
 320         }
 321
 322         advise("after resolving the conflicts, mark the corrected paths");
 323         advise("with 'git add <paths>' or 'git rm <paths>'");
 324         advise("and commit the result with 'git commit'");
 325 }
 326
 327 static void write_message(struct strbuf *msgbuf, const char *filename)
 328 {
 329         static struct lock_file msg_file;
 330
 331         int msg_fd = hold_lock_file_for_update(&msg_file, filename,
 332                                                LOCK_DIE_ON_ERROR);
 333         if (write_in_full(msg_fd, msgbuf->buf, msgbuf->len) < 0)
 334                 die_errno(_("Could not write to %s."), filename);
 335         strbuf_release(msgbuf);
 336         if (commit_lock_file(&msg_file) < 0)
 337                 die(_("Error wrapping up %s"), filename);
 338 }
 339
 340 static struct tree *empty_tree(void)
 341 {
 342         struct tree *tree = xcalloc(1, sizeof(struct tree));
 343
 344         tree->object.parsed = 1;
 345         tree->object.type = OBJ_TREE;
 346         pretend_sha1_file(NULL, 0, OBJ_TREE, tree->object.sha1);
 347         return tree;
 348 }
 349
 350 static int error_dirty_index(struct replay_opts *opts)
 351 {
 352         if (read_cache_unmerged())
 353                 return error_resolve_conflict(action_name(opts));
 354
 355         /* Different translation strings for cherry-pick and revert */
 356         if (opts->action == CHERRY_PICK)
 357                 error(_("Your local changes would be overwritten by cherry-pick."));
 358         else
 359                 error(_("Your local changes would be overwritten by revert."));
 360
 361         if (advice_commit_before_merge)
 362                 advise(_("Commit your changes or stash them to proceed."));
 363         return -1;
 364 }
 365
 366 static int fast_forward_to(const unsigned char *to, const unsigned char *from)
 367 {
 368         struct ref_lock *ref_lock;
 369
 370         read_cache();
 371         if (checkout_fast_forward(from, to))
 372                 exit(1); /* the callee should have complained already */
 373         ref_lock = lock_any_ref_for_update("HEAD", from, 0);
 374         return write_ref_sha1(ref_lock, to, "cherry-pick");
 375 }
 376
 377 static int do_recursive_merge(struct commit *base, struct commit *next,
 378                               const char *base_label, const char *next_label,
 379                               unsigned char *head, struct strbuf *msgbuf,
 380                               struct replay_opts *opts)
 381 {
 382         struct merge_options o;
 383         struct tree *result, *next_tree, *base_tree, *head_tree;
 384         int clean, index_fd;
 385         const char **xopt;
 386         static struct lock_file index_lock;
 387
 388         index_fd = hold_locked_index(&index_lock, 1);
 389
 390         read_cache();
 391
 392         init_merge_options(&o);
 393         o.ancestor = base ? base_label : "(empty tree)";
 394         o.branch1 = "HEAD";
 395         o.branch2 = next ? next_label : "(empty tree)";
 396
 397         head_tree = parse_tree_indirect(head);
 398         next_tree = next ? next->tree : empty_tree();
 399         base_tree = base ? base->tree : empty_tree();
 400
 401         for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
 402                 parse_merge_opt(&o, *xopt);
 403
 404         clean = merge_trees(&o,
 405                             head_tree,
 406                             next_tree, base_tree, &result);
 407
 408         if (active_cache_changed &&
 409             (write_cache(index_fd, active_cache, active_nr) ||
 410              commit_locked_index(&index_lock)))
 411                 /* TRANSLATORS: %s will be "revert" or "cherry-pick" */
 412                 die(_("%s: Unable to write new index file"), action_name(opts));
 413         rollback_lock_file(&index_lock);
 414
 415         if (!clean) {
 416                 int i;
 417                 strbuf_addstr(msgbuf, "\nConflicts:\n\n");
 418                 for (i = 0; i < active_nr;) {
 419                         struct cache_entry *ce = active_cache[i++];
 420                         if (ce_stage(ce)) {
 421                                 strbuf_addch(msgbuf, '\t');
 422                                 strbuf_addstr(msgbuf, ce->name);
 423                                 strbuf_addch(msgbuf, '\n');
 424                                 while (i < active_nr && !strcmp(ce->name,
 425                                                 active_cache[i]->name))
 426                                         i++;
 427                         }
 428                 }
 429         }
 430
 431         return !clean;
 432 }
 433
 434 /*
 435  * If we are cherry-pick, and if the merge did not result in
 436  * hand-editing, we will hit this commit and inherit the original
 437  * author date and name.
 438  * If we are revert, or if our cherry-pick results in a hand merge,
 439  * we had better say that the current user is responsible for that.
 440  */
 441 static int run_git_commit(const char *defmsg, struct replay_opts *opts)
 442 {
 443         /* 6 is max possible length of our args array including NULL */
 444         const char *args[6];
 445         int i = 0;
 446
 447         args[i++] = "commit";
 448         args[i++] = "-n";
 449         if (opts->signoff)
 450                 args[i++] = "-s";
 451         if (!opts->edit) {
 452                 args[i++] = "-F";
 453                 args[i++] = defmsg;
 454         }
 455         args[i] = NULL;
 456
 457         return run_command_v_opt(args, RUN_GIT_CMD);
 458 }
 459
 460 static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
 461 {
 462         unsigned char head[20];
 463         struct commit *base, *next, *parent;
 464         const char *base_label, *next_label;
 465         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 466         char *defmsg = NULL;
 467         struct strbuf msgbuf = STRBUF_INIT;
 468         int res;
 469
 470         if (opts->no_commit) {
 471                 /*
 472                  * We do not intend to commit immediately.  We just want to
 473                  * merge the differences in, so let's compute the tree
 474                  * that represents the "current" state for merge-recursive
 475                  * to work on.
 476                  */
 477                 if (write_cache_as_tree(head, 0, NULL))
 478                         die (_("Your index file is unmerged."));
 479         } else {
 480                 if (get_sha1("HEAD", head))
 481                         return error(_("You do not have a valid HEAD"));
 482                 if (index_differs_from("HEAD", 0))
 483                         return error_dirty_index(opts);
 484         }
 485         discard_cache();
 486
 487         if (!commit->parents) {
 488                 parent = NULL;
 489         }
 490         else if (commit->parents->next) {
 491                 /* Reverting or cherry-picking a merge commit */
 492                 int cnt;
 493                 struct commit_list *p;
 494
 495                 if (!opts->mainline)
 496                         return error(_("Commit %s is a merge but no -m option was given."),
 497                                 sha1_to_hex(commit->object.sha1));
 498
 499                 for (cnt = 1, p = commit->parents;
 500                      cnt != opts->mainline && p;
 501                      cnt++)
 502                         p = p->next;
 503                 if (cnt != opts->mainline || !p)
 504                         return error(_("Commit %s does not have parent %d"),
 505                                 sha1_to_hex(commit->object.sha1), opts->mainline);
 506                 parent = p->item;
 507         } else if (0 < opts->mainline)
 508                 return error(_("Mainline was specified but commit %s is not a merge."),
 509                         sha1_to_hex(commit->object.sha1));
 510         else
 511                 parent = commit->parents->item;
 512
 513         if (opts->allow_ff && parent && !hashcmp(parent->object.sha1, head))
 514                 return fast_forward_to(commit->object.sha1, head);
 515
 516         if (parent && parse_commit(parent) < 0)
 517                 /* TRANSLATORS: The first %s will be "revert" or
 518                    "cherry-pick", the second %s a SHA1 */
 519                 return error(_("%s: cannot parse parent commit %s"),
 520                         action_name(opts), sha1_to_hex(parent->object.sha1));
 521
 522         if (get_message(commit, &msg) != 0)
 523                 return error(_("Cannot get commit message for %s"),
 524                         sha1_to_hex(commit->object.sha1));
 525
 526         /*
 527          * "commit" is an existing commit.  We would want to apply
 528          * the difference it introduces since its first parent "prev"
 529          * on top of the current HEAD if we are cherry-pick.  Or the
 530          * reverse of it if we are revert.
 531          */
 532
 533         defmsg = git_pathdup("MERGE_MSG");
 534
 535         if (opts->action == REVERT) {
 536                 base = commit;
 537                 base_label = msg.label;
 538                 next = parent;
 539                 next_label = msg.parent_label;
 540                 strbuf_addstr(&msgbuf, "Revert \"");
 541                 strbuf_addstr(&msgbuf, msg.subject);
 542                 strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
 543                 strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 544
 545                 if (commit->parents && commit->parents->next) {
 546                         strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
 547                         strbuf_addstr(&msgbuf, sha1_to_hex(parent->object.sha1));
 548                 }
 549                 strbuf_addstr(&msgbuf, ".\n");
 550         } else {
 551                 const char *p;
 552
 553                 base = parent;
 554                 base_label = msg.parent_label;
 555                 next = commit;
 556                 next_label = msg.label;
 557
 558                 /*
 559                  * Append the commit log message to msgbuf; it starts
 560                  * after the tree, parent, author, committer
 561                  * information followed by "\n\n".
 562                  */
 563                 p = strstr(msg.message, "\n\n");
 564                 if (p) {
 565                         p += 2;
 566                         strbuf_addstr(&msgbuf, p);
 567                 }
 568
 569                 if (opts->record_origin) {
 570                         strbuf_addstr(&msgbuf, "(cherry picked from commit ");
 571                         strbuf_addstr(&msgbuf, sha1_to_hex(commit->object.sha1));
 572                         strbuf_addstr(&msgbuf, ")\n");
 573                 }
 574                 if (!opts->no_commit)
 575                         write_cherry_pick_head(commit);
 576         }
 577
 578         if (!opts->strategy || !strcmp(opts->strategy, "recursive") || opts->action == REVERT) {
 579                 res = do_recursive_merge(base, next, base_label, next_label,
 580                                          head, &msgbuf, opts);
 581                 write_message(&msgbuf, defmsg);
 582         } else {
 583                 struct commit_list *common = NULL;
 584                 struct commit_list *remotes = NULL;
 585
 586                 write_message(&msgbuf, defmsg);
 587
 588                 commit_list_insert(base, &common);
 589                 commit_list_insert(next, &remotes);
 590                 res = try_merge_command(opts->strategy, opts->xopts_nr, opts->xopts,
 591                                         common, sha1_to_hex(head), remotes);
 592                 free_commit_list(common);
 593                 free_commit_list(remotes);
 594         }
 595
 596         if (res) {
 597                 error(opts->action == REVERT
 598                       ? _("could not revert %s... %s")
 599                       : _("could not apply %s... %s"),
 600                       find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV),
 601                       msg.subject);
 602                 print_advice();
 603                 rerere(opts->allow_rerere_auto);
 604         } else {
 605                 if (!opts->no_commit)
 606                         res = run_git_commit(defmsg, opts);
 607         }
 608
 609         free_message(&msg);
 610         free(defmsg);
 611
 612         return res;
 613 }
 614
 615 static void prepare_revs(struct rev_info *revs, struct replay_opts *opts)
 616 {
 617         int argc;
 618
 619         init_revisions(revs, NULL);
 620         revs->no_walk = 1;
 621         if (opts->action != REVERT)
 622                 revs->reverse = 1;
 623
 624         argc = setup_revisions(opts->commit_argc, opts->commit_argv, revs, NULL);
 625         if (argc > 1)
 626                 usage(*revert_or_cherry_pick_usage(opts));
 627
 628         if (prepare_revision_walk(revs))
 629                 die(_("revision walk setup failed"));
 630
 631         if (!revs->commits)
 632                 die(_("empty commit set passed"));
 633 }
 634
 635 static void read_and_refresh_cache(struct replay_opts *opts)
 636 {
 637         static struct lock_file index_lock;
 638         int index_fd = hold_locked_index(&index_lock, 0);
 639         if (read_index_preload(&the_index, NULL) < 0)
 640                 die(_("git %s: failed to read the index"), action_name(opts));
 641         refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
 642         if (the_index.cache_changed) {
 643                 if (write_index(&the_index, index_fd) ||
 644                     commit_locked_index(&index_lock))
 645                         die(_("git %s: failed to refresh the index"), action_name(opts));
 646         }
 647         rollback_lock_file(&index_lock);
 648 }
 649
 650 /*
 651  * Append a commit to the end of the commit_list.
 652  *
 653  * next starts by pointing to the variable that holds the head of an
 654  * empty commit_list, and is updated to point to the "next" field of
 655  * the last item on the list as new commits are appended.
 656  *
 657  * Usage example:
 658  *
 659  *     struct commit_list *list;
 660  *     struct commit_list **next = &list;
 661  *
 662  *     next = commit_list_append(c1, next);
 663  *     next = commit_list_append(c2, next);
 664  *     assert(commit_list_count(list) == 2);
 665  *     return list;
 666  */
 667 struct commit_list **commit_list_append(struct commit *commit,
 668                                         struct commit_list **next)
 669 {
 670         struct commit_list *new = xmalloc(sizeof(struct commit_list));
 671         new->item = commit;
 672         *next = new;
 673         new->next = NULL;
 674         return &new->next;
 675 }
 676
 677 static int format_todo(struct strbuf *buf, struct commit_list *todo_list,
 678                 struct replay_opts *opts)
 679 {
 680         struct commit_list *cur = NULL;
 681         struct commit_message msg = { NULL, NULL, NULL, NULL, NULL };
 682         const char *sha1_abbrev = NULL;
 683         const char *action_str = opts->action == REVERT ? "revert" : "pick";
 684
 685         for (cur = todo_list; cur; cur = cur->next) {
 686                 sha1_abbrev = find_unique_abbrev(cur->item->object.sha1, DEFAULT_ABBREV);
 687                 if (get_message(cur->item, &msg))
 688                         return error(_("Cannot get commit message for %s"), sha1_abbrev);
 689                 strbuf_addf(buf, "%s %s %s\n", action_str, sha1_abbrev, msg.subject);
 690         }
 691         return 0;
 692 }
 693
 694 static struct commit *parse_insn_line(char *start, struct replay_opts *opts)
 695 {
 696         unsigned char commit_sha1[20];
 697         char sha1_abbrev[40];
 698         enum replay_action action;
 699         int insn_len = 0;
 700         char *p, *q;
 701
 702         if (!prefixcmp(start, "pick ")) {
 703                 action = CHERRY_PICK;
 704                 insn_len = strlen("pick");
 705                 p = start + insn_len + 1;
 706         } else if (!prefixcmp(start, "revert ")) {
 707                 action = REVERT;
 708                 insn_len = strlen("revert");
 709                 p = start + insn_len + 1;
 710         } else
 711                 return NULL;
 712
 713         q = strchr(p, ' ');
 714         if (!q)
 715                 return NULL;
 716         q++;
 717
 718         strlcpy(sha1_abbrev, p, q - p);
 719
 720         /*
 721          * Verify that the action matches up with the one in
 722          * opts; we don't support arbitrary instructions
 723          */
 724         if (action != opts->action) {
 725                 const char *action_str;
 726                 action_str = action == REVERT ? "revert" : "cherry-pick";
 727                 error(_("Cannot %s during a %s"), action_str, action_name(opts));
 728                 return NULL;
 729         }
 730
 731         if (get_sha1(sha1_abbrev, commit_sha1) < 0)
 732                 return NULL;
 733
 734         return lookup_commit_reference(commit_sha1);
 735 }
 736
 737 static int parse_insn_buffer(char *buf, struct commit_list **todo_list,
 738                         struct replay_opts *opts)
 739 {
 740         struct commit_list **next = todo_list;
 741         struct commit *commit;
 742         char *p = buf;
 743         int i;
 744
 745         for (i = 1; *p; i++) {
 746                 commit = parse_insn_line(p, opts);
 747                 if (!commit)
 748                         return error(_("Could not parse line %d."), i);
 749                 next = commit_list_append(commit, next);
 750                 p = strchrnul(p, '\n');
 751                 if (*p)
 752                         p++;
 753         }
 754         if (!*todo_list)
 755                 return error(_("No commits parsed."));
 756         return 0;
 757 }
 758
 759 static void read_populate_todo(struct commit_list **todo_list,
 760                         struct replay_opts *opts)
 761 {
 762         const char *todo_file = git_path(SEQ_TODO_FILE);
 763         struct strbuf buf = STRBUF_INIT;
 764         int fd, res;
 765
 766         fd = open(todo_file, O_RDONLY);
 767         if (fd < 0)
 768                 die_errno(_("Could not open %s."), todo_file);
 769         if (strbuf_read(&buf, fd, 0) < 0) {
 770                 close(fd);
 771                 strbuf_release(&buf);
 772                 die(_("Could not read %s."), todo_file);
 773         }
 774         close(fd);
 775
 776         res = parse_insn_buffer(buf.buf, todo_list, opts);
 777         strbuf_release(&buf);
 778         if (res)
 779                 die(_("Unusable instruction sheet: %s"), todo_file);
 780 }
 781
 782 static int populate_opts_cb(const char *key, const char *value, void *data)
 783 {
 784         struct replay_opts *opts = data;
 785         int error_flag = 1;
 786
 787         if (!value)
 788                 error_flag = 0;
 789         else if (!strcmp(key, "options.no-commit"))
 790                 opts->no_commit = git_config_bool_or_int(key, value, &error_flag);
 791         else if (!strcmp(key, "options.edit"))
 792                 opts->edit = git_config_bool_or_int(key, value, &error_flag);
 793         else if (!strcmp(key, "options.signoff"))
 794                 opts->signoff = git_config_bool_or_int(key, value, &error_flag);
 795         else if (!strcmp(key, "options.record-origin"))
 796                 opts->record_origin = git_config_bool_or_int(key, value, &error_flag);
 797         else if (!strcmp(key, "options.allow-ff"))
 798                 opts->allow_ff = git_config_bool_or_int(key, value, &error_flag);
 799         else if (!strcmp(key, "options.mainline"))
 800                 opts->mainline = git_config_int(key, value);
 801         else if (!strcmp(key, "options.strategy"))
 802                 git_config_string(&opts->strategy, key, value);
 803         else if (!strcmp(key, "options.strategy-option")) {
 804                 ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
 805                 opts->xopts[opts->xopts_nr++] = xstrdup(value);
 806         } else
 807                 return error(_("Invalid key: %s"), key);
 808
 809         if (!error_flag)
 810                 return error(_("Invalid value for %s: %s"), key, value);
 811
 812         return 0;
 813 }
 814
 815 static void read_populate_opts(struct replay_opts **opts_ptr)
 816 {
 817         const char *opts_file = git_path(SEQ_OPTS_FILE);
 818
 819         if (!file_exists(opts_file))
 820                 return;
 821         if (git_config_from_file(populate_opts_cb, opts_file, *opts_ptr) < 0)
 822                 die(_("Malformed options sheet: %s"), opts_file);
 823 }
 824
 825 static void walk_revs_populate_todo(struct commit_list **todo_list,
 826                                 struct replay_opts *opts)
 827 {
 828         struct rev_info revs;
 829         struct commit *commit;
 830         struct commit_list **next;
 831
 832         prepare_revs(&revs, opts);
 833
 834         next = todo_list;
 835         while ((commit = get_revision(&revs)))
 836                 next = commit_list_append(commit, next);
 837 }
 838
 839 static int create_seq_dir(void)
 840 {
 841         const char *seq_dir = git_path(SEQ_DIR);
 842
 843         if (file_exists(seq_dir))
 844                 return error(_("%s already exists."), seq_dir);
 845         else if (mkdir(seq_dir, 0777) < 0)
 846                 die_errno(_("Could not create sequencer directory '%s'."), seq_dir);
 847         return 0;
 848 }
 849
 850 static void save_head(const char *head)
 851 {
 852         const char *head_file = git_path(SEQ_HEAD_FILE);
 853         static struct lock_file head_lock;
 854         struct strbuf buf = STRBUF_INIT;
 855         int fd;
 856
 857         fd = hold_lock_file_for_update(&head_lock, head_file, LOCK_DIE_ON_ERROR);
 858         strbuf_addf(&buf, "%s\n", head);
 859         if (write_in_full(fd, buf.buf, buf.len) < 0)
 860                 die_errno(_("Could not write to %s."), head_file);
 861         if (commit_lock_file(&head_lock) < 0)
 862                 die(_("Error wrapping up %s."), head_file);
 863 }
 864
 865 static void save_todo(struct commit_list *todo_list, struct replay_opts *opts)
 866 {
 867         const char *todo_file = git_path(SEQ_TODO_FILE);
 868         static struct lock_file todo_lock;
 869         struct strbuf buf = STRBUF_INIT;
 870         int fd;
 871
 872         fd = hold_lock_file_for_update(&todo_lock, todo_file, LOCK_DIE_ON_ERROR);
 873         if (format_todo(&buf, todo_list, opts) < 0)
 874                 die(_("Could not format %s."), todo_file);
 875         if (write_in_full(fd, buf.buf, buf.len) < 0) {
 876                 strbuf_release(&buf);
 877                 die_errno(_("Could not write to %s."), todo_file);
 878         }
 879         if (commit_lock_file(&todo_lock) < 0) {
 880                 strbuf_release(&buf);
 881                 die(_("Error wrapping up %s."), todo_file);
 882         }
 883         strbuf_release(&buf);
 884 }
 885
 886 static void save_opts(struct replay_opts *opts)
 887 {
 888         const char *opts_file = git_path(SEQ_OPTS_FILE);
 889
 890         if (opts->no_commit)
 891                 git_config_set_in_file(opts_file, "options.no-commit", "true");
 892         if (opts->edit)
 893                 git_config_set_in_file(opts_file, "options.edit", "true");
 894         if (opts->signoff)
 895                 git_config_set_in_file(opts_file, "options.signoff", "true");
 896         if (opts->record_origin)
 897                 git_config_set_in_file(opts_file, "options.record-origin", "true");
 898         if (opts->allow_ff)
 899                 git_config_set_in_file(opts_file, "options.allow-ff", "true");
 900         if (opts->mainline) {
 901                 struct strbuf buf = STRBUF_INIT;
 902                 strbuf_addf(&buf, "%d", opts->mainline);
 903                 git_config_set_in_file(opts_file, "options.mainline", buf.buf);
 904                 strbuf_release(&buf);
 905         }
 906         if (opts->strategy)
 907                 git_config_set_in_file(opts_file, "options.strategy", opts->strategy);
 908         if (opts->xopts) {
 909                 int i;
 910                 for (i = 0; i < opts->xopts_nr; i++)
 911                         git_config_set_multivar_in_file(opts_file,
 912                                                         "options.strategy-option",
 913                                                         opts->xopts[i], "^$", 0);
 914         }
 915 }
 916
 917 static int pick_commits(struct commit_list *todo_list, struct replay_opts *opts)
 918 {
 919         struct commit_list *cur;
 920         int res;
 921
 922         setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
 923         if (opts->allow_ff)
 924                 assert(!(opts->signoff || opts->no_commit ||
 925                                 opts->record_origin || opts->edit));
 926         read_and_refresh_cache(opts);
 927
 928         for (cur = todo_list; cur; cur = cur->next) {
 929                 save_todo(cur, opts);
 930                 res = do_pick_commit(cur->item, opts);
 931                 if (res) {
 932                         if (!cur->next)
 933                                 /*
 934                                  * An error was encountered while
 935                                  * picking the last commit; the
 936                                  * sequencer state is useless now --
 937                                  * the user simply needs to resolve
 938                                  * the conflict and commit
 939                                  */
 940                                 remove_sequencer_state(0);
 941                         return res;
 942                 }
 943         }
 944
 945         /*
 946          * Sequence of picks finished successfully; cleanup by
 947          * removing the .git/sequencer directory
 948          */
 949         remove_sequencer_state(1);
 950         return 0;
 951 }
 952
 953 static int pick_revisions(struct replay_opts *opts)
 954 {
 955         struct commit_list *todo_list = NULL;
 956         unsigned char sha1[20];
 957
 958         read_and_refresh_cache(opts);
 959
 960         /*
 961          * Decide what to do depending on the arguments; a fresh
 962          * cherry-pick should be handled differently from an existing
 963          * one that is being continued
 964          */
 965         if (opts->subcommand == REPLAY_RESET) {
 966                 remove_sequencer_state(1);
 967                 return 0;
 968         } else if (opts->subcommand == REPLAY_CONTINUE) {
 969                 if (!file_exists(git_path(SEQ_TODO_FILE)))
 970                         goto error;
 971                 read_populate_opts(&opts);
 972                 read_populate_todo(&todo_list, opts);
 973
 974                 /* Verify that the conflict has been resolved */
 975                 if (!index_differs_from("HEAD", 0))
 976                         todo_list = todo_list->next;
 977         } else {
 978                 /*
 979                  * Start a new cherry-pick/ revert sequence; but
 980                  * first, make sure that an existing one isn't in
 981                  * progress
 982                  */
 983
 984                 walk_revs_populate_todo(&todo_list, opts);
 985                 if (create_seq_dir() < 0) {
 986                         error(_("A cherry-pick or revert is in progress."));
 987                         advise(_("Use --continue to continue the operation"));
 988                         advise(_("or --reset to forget about it"));
 989                         return -1;
 990                 }
 991                 if (get_sha1("HEAD", sha1)) {
 992                         if (opts->action == REVERT)
 993                                 return error(_("Can't revert as initial commit"));
 994                         return error(_("Can't cherry-pick into empty head"));
 995                 }
 996                 save_head(sha1_to_hex(sha1));
 997                 save_opts(opts);
 998         }
 999         return pick_commits(todo_list, opts);
1000 error:
1001         return error(_("No %s in progress"), action_name(opts));
1002 }
1003
1004 int cmd_revert(int argc, const char **argv, const char *prefix)
1005 {
1006         struct replay_opts opts;
1007         int res;
1008
1009         memset(&opts, 0, sizeof(opts));
1010         if (isatty(0))
1011                 opts.edit = 1;
1012         opts.action = REVERT;
1013         git_config(git_default_config, NULL);
1014         parse_args(argc, argv, &opts);
1015         res = pick_revisions(&opts);
1016         if (res < 0)
1017                 die(_("revert failed"));
1018         return res;
1019 }
1020
1021 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
1022 {
1023         struct replay_opts opts;
1024         int res;
1025
1026         memset(&opts, 0, sizeof(opts));
1027         opts.action = CHERRY_PICK;
1028         git_config(git_default_config, NULL);
1029         parse_args(argc, argv, &opts);
1030         res = pick_revisions(&opts);
1031         if (res < 0)
1032                 die(_("cherry-pick failed"));
1033         return res;
1034 }