c3e34d10d9bacff099fa7c3fadada324eff0314b
   1#include "cache.h"
   2#include "lockfile.h"
   3#include "string-list.h"
   4#include "rerere.h"
   5#include "xdiff-interface.h"
   6#include "dir.h"
   7#include "resolve-undo.h"
   8#include "ll-merge.h"
   9#include "attr.h"
  10#include "pathspec.h"
  11
  12#define RESOLVED 0
  13#define PUNTED 1
  14#define THREE_STAGED 2
  15void *RERERE_RESOLVED = &RERERE_RESOLVED;
  16
  17/* if rerere_enabled == -1, fall back to detection of .git/rr-cache */
  18static int rerere_enabled = -1;
  19
  20/* automatically update cleanly resolved paths to the index */
  21static int rerere_autoupdate;
  22
  23static char *merge_rr_path;
  24
  25const char *rerere_path(const char *hex, const char *file)
  26{
  27        return git_path("rr-cache/%s/%s", hex, file);
  28}
  29
  30static int has_rerere_resolution(const char *hex)
  31{
  32        struct stat st;
  33        return !stat(rerere_path(hex, "postimage"), &st);
  34}
  35
  36/*
  37 * $GIT_DIR/MERGE_RR file is a collection of records, each of which is
  38 * "conflict ID", a HT and pathname, terminated with a NUL, and is
  39 * used to keep track of the set of paths that "rerere" may need to
  40 * work on (i.e. what is left by the previous invocation of "git
  41 * rerere" during the current conflict resolution session).
  42 */
  43static void read_rr(struct string_list *rr)
  44{
  45        struct strbuf buf = STRBUF_INIT;
  46        FILE *in = fopen(merge_rr_path, "r");
  47
  48        if (!in)
  49                return;
  50        while (!strbuf_getwholeline(&buf, in, '\0')) {
  51                char *path;
  52                unsigned char sha1[20];
  53
  54                /* There has to be the hash, tab, path and then NUL */
  55                if (buf.len < 42 || get_sha1_hex(buf.buf, sha1))
  56                        die("corrupt MERGE_RR");
  57
  58                if (buf.buf[40] != '\t')
  59                        die("corrupt MERGE_RR");
  60                buf.buf[40] = '\0';
  61                path = buf.buf + 41;
  62
  63                string_list_insert(rr, path)->util = xstrdup(buf.buf);
  64        }
  65        strbuf_release(&buf);
  66        fclose(in);
  67}
  68
  69static struct lock_file write_lock;
  70
  71static int write_rr(struct string_list *rr, int out_fd)
  72{
  73        int i;
  74        for (i = 0; i < rr->nr; i++) {
  75                struct strbuf buf = STRBUF_INIT;
  76
  77                assert(rr->items[i].util != RERERE_RESOLVED);
  78                if (!rr->items[i].util)
  79                        continue;
  80                strbuf_addf(&buf, "%s\t%s%c",
  81                            (char *)rr->items[i].util,
  82                            rr->items[i].string, 0);
  83                if (write_in_full(out_fd, buf.buf, buf.len) != buf.len)
  84                        die("unable to write rerere record");
  85
  86                strbuf_release(&buf);
  87        }
  88        if (commit_lock_file(&write_lock) != 0)
  89                die("unable to write rerere record");
  90        return 0;
  91}
  92
  93/*
  94 * "rerere" interacts with conflicted file contents using this I/O
  95 * abstraction.  It reads a conflicted contents from one place via
  96 * "getline()" method, and optionally can write it out after
  97 * normalizing the conflicted hunks to the "output".  Subclasses of
  98 * rerere_io embed this structure at the beginning of their own
  99 * rerere_io object.
 100 */
 101struct rerere_io {
 102        int (*getline)(struct strbuf *, struct rerere_io *);
 103        FILE *output;
 104        int wrerror;
 105        /* some more stuff */
 106};
 107
 108static void ferr_write(const void *p, size_t count, FILE *fp, int *err)
 109{
 110        if (!count || *err)
 111                return;
 112        if (fwrite(p, count, 1, fp) != 1)
 113                *err = errno;
 114}
 115
 116static inline void ferr_puts(const char *s, FILE *fp, int *err)
 117{
 118        ferr_write(s, strlen(s), fp, err);
 119}
 120
 121static void rerere_io_putstr(const char *str, struct rerere_io *io)
 122{
 123        if (io->output)
 124                ferr_puts(str, io->output, &io->wrerror);
 125}
 126
 127/*
 128 * Write a conflict marker to io->output (if defined).
 129 */
 130static void rerere_io_putconflict(int ch, int size, struct rerere_io *io)
 131{
 132        char buf[64];
 133
 134        while (size) {
 135                if (size <= sizeof(buf) - 2) {
 136                        memset(buf, ch, size);
 137                        buf[size] = '\n';
 138                        buf[size + 1] = '\0';
 139                        size = 0;
 140                } else {
 141                        int sz = sizeof(buf) - 1;
 142
 143                        /*
 144                         * Make sure we will not write everything out
 145                         * in this round by leaving at least 1 byte
 146                         * for the next round, giving the next round
 147                         * a chance to add the terminating LF.  Yuck.
 148                         */
 149                        if (size <= sz)
 150                                sz -= (sz - size) + 1;
 151                        memset(buf, ch, sz);
 152                        buf[sz] = '\0';
 153                        size -= sz;
 154                }
 155                rerere_io_putstr(buf, io);
 156        }
 157}
 158
 159static void rerere_io_putmem(const char *mem, size_t sz, struct rerere_io *io)
 160{
 161        if (io->output)
 162                ferr_write(mem, sz, io->output, &io->wrerror);
 163}
 164
 165/*
 166 * Subclass of rerere_io that reads from an on-disk file
 167 */
 168struct rerere_io_file {
 169        struct rerere_io io;
 170        FILE *input;
 171};
 172
 173/*
 174 * ... and its getline() method implementation
 175 */
 176static int rerere_file_getline(struct strbuf *sb, struct rerere_io *io_)
 177{
 178        struct rerere_io_file *io = (struct rerere_io_file *)io_;
 179        return strbuf_getwholeline(sb, io->input, '\n');
 180}
 181
 182/*
 183 * Require the exact number of conflict marker letters, no more, no
 184 * less, followed by SP or any whitespace
 185 * (including LF).
 186 */
 187static int is_cmarker(char *buf, int marker_char, int marker_size)
 188{
 189        int want_sp;
 190
 191        /*
 192         * The beginning of our version and the end of their version
 193         * always are labeled like "<<<<< ours" or ">>>>> theirs",
 194         * hence we set want_sp for them.  Note that the version from
 195         * the common ancestor in diff3-style output is not always
 196         * labelled (e.g. "||||| common" is often seen but "|||||"
 197         * alone is also valid), so we do not set want_sp.
 198         */
 199        want_sp = (marker_char == '<') || (marker_char == '>');
 200
 201        while (marker_size--)
 202                if (*buf++ != marker_char)
 203                        return 0;
 204        if (want_sp && *buf != ' ')
 205                return 0;
 206        return isspace(*buf);
 207}
 208
 209/*
 210 * Read contents a file with conflicts, normalize the conflicts
 211 * by (1) discarding the common ancestor version in diff3-style,
 212 * (2) reordering our side and their side so that whichever sorts
 213 * alphabetically earlier comes before the other one, while
 214 * computing the "conflict ID", which is just an SHA-1 hash of
 215 * one side of the conflict, NUL, the other side of the conflict,
 216 * and NUL concatenated together.
 217 *
 218 * Return the number of conflict hunks found.
 219 *
 220 * NEEDSWORK: the logic and theory of operation behind this conflict
 221 * normalization may deserve to be documented somewhere, perhaps in
 222 * Documentation/technical/rerere.txt.
 223 */
 224static int handle_path(unsigned char *sha1, struct rerere_io *io, int marker_size)
 225{
 226        git_SHA_CTX ctx;
 227        int hunk_no = 0;
 228        enum {
 229                RR_CONTEXT = 0, RR_SIDE_1, RR_SIDE_2, RR_ORIGINAL
 230        } hunk = RR_CONTEXT;
 231        struct strbuf one = STRBUF_INIT, two = STRBUF_INIT;
 232        struct strbuf buf = STRBUF_INIT;
 233
 234        if (sha1)
 235                git_SHA1_Init(&ctx);
 236
 237        while (!io->getline(&buf, io)) {
 238                if (is_cmarker(buf.buf, '<', marker_size)) {
 239                        if (hunk != RR_CONTEXT)
 240                                goto bad;
 241                        hunk = RR_SIDE_1;
 242                } else if (is_cmarker(buf.buf, '|', marker_size)) {
 243                        if (hunk != RR_SIDE_1)
 244                                goto bad;
 245                        hunk = RR_ORIGINAL;
 246                } else if (is_cmarker(buf.buf, '=', marker_size)) {
 247                        if (hunk != RR_SIDE_1 && hunk != RR_ORIGINAL)
 248                                goto bad;
 249                        hunk = RR_SIDE_2;
 250                } else if (is_cmarker(buf.buf, '>', marker_size)) {
 251                        if (hunk != RR_SIDE_2)
 252                                goto bad;
 253                        if (strbuf_cmp(&one, &two) > 0)
 254                                strbuf_swap(&one, &two);
 255                        hunk_no++;
 256                        hunk = RR_CONTEXT;
 257                        rerere_io_putconflict('<', marker_size, io);
 258                        rerere_io_putmem(one.buf, one.len, io);
 259                        rerere_io_putconflict('=', marker_size, io);
 260                        rerere_io_putmem(two.buf, two.len, io);
 261                        rerere_io_putconflict('>', marker_size, io);
 262                        if (sha1) {
 263                                git_SHA1_Update(&ctx, one.buf ? one.buf : "",
 264                                            one.len + 1);
 265                                git_SHA1_Update(&ctx, two.buf ? two.buf : "",
 266                                            two.len + 1);
 267                        }
 268                        strbuf_reset(&one);
 269                        strbuf_reset(&two);
 270                } else if (hunk == RR_SIDE_1)
 271                        strbuf_addbuf(&one, &buf);
 272                else if (hunk == RR_ORIGINAL)
 273                        ; /* discard */
 274                else if (hunk == RR_SIDE_2)
 275                        strbuf_addbuf(&two, &buf);
 276                else
 277                        rerere_io_putstr(buf.buf, io);
 278                continue;
 279        bad:
 280                hunk = 99; /* force error exit */
 281                break;
 282        }
 283        strbuf_release(&one);
 284        strbuf_release(&two);
 285        strbuf_release(&buf);
 286
 287        if (sha1)
 288                git_SHA1_Final(sha1, &ctx);
 289        if (hunk != RR_CONTEXT)
 290                return -1;
 291        return hunk_no;
 292}
 293
 294/*
 295 * Scan the path for conflicts, do the "handle_path()" thing above, and
 296 * return the number of conflict hunks found.
 297 */
 298static int handle_file(const char *path, unsigned char *sha1, const char *output)
 299{
 300        int hunk_no = 0;
 301        struct rerere_io_file io;
 302        int marker_size = ll_merge_marker_size(path);
 303
 304        memset(&io, 0, sizeof(io));
 305        io.io.getline = rerere_file_getline;
 306        io.input = fopen(path, "r");
 307        io.io.wrerror = 0;
 308        if (!io.input)
 309                return error("Could not open %s", path);
 310
 311        if (output) {
 312                io.io.output = fopen(output, "w");
 313                if (!io.io.output) {
 314                        fclose(io.input);
 315                        return error("Could not write %s", output);
 316                }
 317        }
 318
 319        hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
 320
 321        fclose(io.input);
 322        if (io.io.wrerror)
 323                error("There were errors while writing %s (%s)",
 324                      path, strerror(io.io.wrerror));
 325        if (io.io.output && fclose(io.io.output))
 326                io.io.wrerror = error("Failed to flush %s: %s",
 327                                      path, strerror(errno));
 328
 329        if (hunk_no < 0) {
 330                if (output)
 331                        unlink_or_warn(output);
 332                return error("Could not parse conflict hunks in %s", path);
 333        }
 334        if (io.io.wrerror)
 335                return -1;
 336        return hunk_no;
 337}
 338
 339/*
 340 * Subclass of rerere_io that reads from an in-core buffer that is a
 341 * strbuf
 342 */
 343struct rerere_io_mem {
 344        struct rerere_io io;
 345        struct strbuf input;
 346};
 347
 348/*
 349 * ... and its getline() method implementation
 350 */
 351static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
 352{
 353        struct rerere_io_mem *io = (struct rerere_io_mem *)io_;
 354        char *ep;
 355        size_t len;
 356
 357        strbuf_release(sb);
 358        if (!io->input.len)
 359                return -1;
 360        ep = memchr(io->input.buf, '\n', io->input.len);
 361        if (!ep)
 362                ep = io->input.buf + io->input.len;
 363        else if (*ep == '\n')
 364                ep++;
 365        len = ep - io->input.buf;
 366        strbuf_add(sb, io->input.buf, len);
 367        strbuf_remove(&io->input, 0, len);
 368        return 0;
 369}
 370
 371static int handle_cache(const char *path, unsigned char *sha1, const char *output)
 372{
 373        mmfile_t mmfile[3] = {{NULL}};
 374        mmbuffer_t result = {NULL, 0};
 375        const struct cache_entry *ce;
 376        int pos, len, i, hunk_no;
 377        struct rerere_io_mem io;
 378        int marker_size = ll_merge_marker_size(path);
 379
 380        /*
 381         * Reproduce the conflicted merge in-core
 382         */
 383        len = strlen(path);
 384        pos = cache_name_pos(path, len);
 385        if (0 <= pos)
 386                return -1;
 387        pos = -pos - 1;
 388
 389        while (pos < active_nr) {
 390                enum object_type type;
 391                unsigned long size;
 392
 393                ce = active_cache[pos++];
 394                if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
 395                        break;
 396                i = ce_stage(ce) - 1;
 397                if (!mmfile[i].ptr) {
 398                        mmfile[i].ptr = read_sha1_file(ce->sha1, &type, &size);
 399                        mmfile[i].size = size;
 400                }
 401        }
 402        for (i = 0; i < 3; i++)
 403                if (!mmfile[i].ptr && !mmfile[i].size)
 404                        mmfile[i].ptr = xstrdup("");
 405
 406        /*
 407         * NEEDSWORK: handle conflicts from merges with
 408         * merge.renormalize set, too
 409         */
 410        ll_merge(&result, path, &mmfile[0], NULL,
 411                 &mmfile[1], "ours",
 412                 &mmfile[2], "theirs", NULL);
 413        for (i = 0; i < 3; i++)
 414                free(mmfile[i].ptr);
 415
 416        memset(&io, 0, sizeof(io));
 417        io.io.getline = rerere_mem_getline;
 418        if (output)
 419                io.io.output = fopen(output, "w");
 420        else
 421                io.io.output = NULL;
 422        strbuf_init(&io.input, 0);
 423        strbuf_attach(&io.input, result.ptr, result.size, result.size);
 424
 425        /*
 426         * Grab the conflict ID and optionally write the original
 427         * contents with conflict markers out.
 428         */
 429        hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
 430        strbuf_release(&io.input);
 431        if (io.io.output)
 432                fclose(io.io.output);
 433        return hunk_no;
 434}
 435
 436/*
 437 * Look at a cache entry at "i" and see if it is not conflicting,
 438 * conflicting and we are willing to handle, or conflicting and
 439 * we are unable to handle, and return the determination in *type.
 440 * Return the cache index to be looked at next, by skipping the
 441 * stages we have already looked at in this invocation of this
 442 * function.
 443 */
 444static int check_one_conflict(int i, int *type)
 445{
 446        const struct cache_entry *e = active_cache[i];
 447
 448        if (!ce_stage(e)) {
 449                *type = RESOLVED;
 450                return i + 1;
 451        }
 452
 453        *type = PUNTED;
 454        while (ce_stage(active_cache[i]) == 1)
 455                i++;
 456
 457        /* Only handle regular files with both stages #2 and #3 */
 458        if (i + 1 < active_nr) {
 459                const struct cache_entry *e2 = active_cache[i];
 460                const struct cache_entry *e3 = active_cache[i + 1];
 461                if (ce_stage(e2) == 2 &&
 462                    ce_stage(e3) == 3 &&
 463                    ce_same_name(e, e3) &&
 464                    S_ISREG(e2->ce_mode) &&
 465                    S_ISREG(e3->ce_mode))
 466                        *type = THREE_STAGED;
 467        }
 468
 469        /* Skip the entries with the same name */
 470        while (i < active_nr && ce_same_name(e, active_cache[i]))
 471                i++;
 472        return i;
 473}
 474
 475/*
 476 * Scan the index and find paths that have conflicts that rerere can
 477 * handle, i.e. the ones that has both stages #2 and #3.
 478 *
 479 * NEEDSWORK: we do not record or replay a previous "resolve by
 480 * deletion" for a delete-modify conflict, as that is inherently risky
 481 * without knowing what modification is being discarded.  The only
 482 * safe case, i.e. both side doing the deletion and modification that
 483 * are identical to the previous round, might want to be handled,
 484 * though.
 485 */
 486static int find_conflict(struct string_list *conflict)
 487{
 488        int i;
 489        if (read_cache() < 0)
 490                return error("Could not read index");
 491
 492        for (i = 0; i < active_nr;) {
 493                int conflict_type;
 494                const struct cache_entry *e = active_cache[i];
 495                i = check_one_conflict(i, &conflict_type);
 496                if (conflict_type == THREE_STAGED)
 497                        string_list_insert(conflict, (const char *)e->name);
 498        }
 499        return 0;
 500}
 501
 502/*
 503 * The merge_rr list is meant to hold outstanding conflicted paths
 504 * that rerere could handle.  Abuse the list by adding other types of
 505 * entries to allow the caller to show "rerere remaining".
 506 *
 507 * - Conflicted paths that rerere does not handle are added
 508 * - Conflicted paths that have been resolved are marked as such
 509 *   by storing RERERE_RESOLVED to .util field (where conflict ID
 510 *   is expected to be stored).
 511 *
 512 * Do *not* write MERGE_RR file out after calling this function.
 513 *
 514 * NEEDSWORK: we may want to fix the caller that implements "rerere
 515 * remaining" to do this without abusing merge_rr.
 516 */
 517int rerere_remaining(struct string_list *merge_rr)
 518{
 519        int i;
 520        if (read_cache() < 0)
 521                return error("Could not read index");
 522
 523        for (i = 0; i < active_nr;) {
 524                int conflict_type;
 525                const struct cache_entry *e = active_cache[i];
 526                i = check_one_conflict(i, &conflict_type);
 527                if (conflict_type == PUNTED)
 528                        string_list_insert(merge_rr, (const char *)e->name);
 529                else if (conflict_type == RESOLVED) {
 530                        struct string_list_item *it;
 531                        it = string_list_lookup(merge_rr, (const char *)e->name);
 532                        if (it != NULL) {
 533                                free(it->util);
 534                                it->util = RERERE_RESOLVED;
 535                        }
 536                }
 537        }
 538        return 0;
 539}
 540
 541/*
 542 * Find the conflict identified by "name"; the change between its
 543 * "preimage" (i.e. a previous contents with conflict markers) and its
 544 * "postimage" (i.e. the corresponding contents with conflicts
 545 * resolved) may apply cleanly to the contents stored in "path", i.e.
 546 * the conflict this time around.
 547 *
 548 * Returns 0 for successful replay of recorded resolution, or non-zero
 549 * for failure.
 550 */
 551static int merge(const char *name, const char *path)
 552{
 553        int ret;
 554        mmfile_t cur = {NULL, 0}, base = {NULL, 0}, other = {NULL, 0};
 555        mmbuffer_t result = {NULL, 0};
 556
 557        /*
 558         * Normalize the conflicts in path and write it out to
 559         * "thisimage" temporary file.
 560         */
 561        if (handle_file(path, NULL, rerere_path(name, "thisimage")) < 0)
 562                return 1;
 563
 564        if (read_mmfile(&cur, rerere_path(name, "thisimage")) ||
 565            read_mmfile(&base, rerere_path(name, "preimage")) ||
 566            read_mmfile(&other, rerere_path(name, "postimage"))) {
 567                ret = 1;
 568                goto out;
 569        }
 570
 571        /*
 572         * A three-way merge. Note that this honors user-customizable
 573         * low-level merge driver settings.
 574         */
 575        ret = ll_merge(&result, path, &base, NULL, &cur, "", &other, "", NULL);
 576        if (!ret) {
 577                FILE *f;
 578
 579                /*
 580                 * A successful replay of recorded resolution.
 581                 * Mark that "postimage" was used to help gc.
 582                 */
 583                if (utime(rerere_path(name, "postimage"), NULL) < 0)
 584                        warning("failed utime() on %s: %s",
 585                                        rerere_path(name, "postimage"),
 586                                        strerror(errno));
 587
 588                /* Update "path" with the resolution */
 589                f = fopen(path, "w");
 590                if (!f)
 591                        return error("Could not open %s: %s", path,
 592                                     strerror(errno));
 593                if (fwrite(result.ptr, result.size, 1, f) != 1)
 594                        error("Could not write %s: %s", path, strerror(errno));
 595                if (fclose(f))
 596                        return error("Writing %s failed: %s", path,
 597                                     strerror(errno));
 598        }
 599
 600out:
 601        free(cur.ptr);
 602        free(base.ptr);
 603        free(other.ptr);
 604        free(result.ptr);
 605
 606        return ret;
 607}
 608
 609static struct lock_file index_lock;
 610
 611static void update_paths(struct string_list *update)
 612{
 613        int i;
 614
 615        hold_locked_index(&index_lock, 1);
 616
 617        for (i = 0; i < update->nr; i++) {
 618                struct string_list_item *item = &update->items[i];
 619                if (add_file_to_cache(item->string, 0))
 620                        exit(128);
 621                fprintf(stderr, "Staged '%s' using previous resolution.\n",
 622                        item->string);
 623        }
 624
 625        if (active_cache_changed) {
 626                if (write_locked_index(&the_index, &index_lock, COMMIT_LOCK))
 627                        die("Unable to write new index file");
 628        } else
 629                rollback_lock_file(&index_lock);
 630}
 631
 632static int do_plain_rerere(struct string_list *rr, int fd)
 633{
 634        struct string_list conflict = STRING_LIST_INIT_DUP;
 635        struct string_list update = STRING_LIST_INIT_DUP;
 636        int i;
 637
 638        find_conflict(&conflict);
 639
 640        /*
 641         * MERGE_RR records paths with conflicts immediately after
 642         * merge failed.  Some of the conflicted paths might have been
 643         * hand resolved in the working tree since then, but the
 644         * initial run would catch all and register their preimages.
 645         */
 646        for (i = 0; i < conflict.nr; i++) {
 647                const char *path = conflict.items[i].string;
 648                if (!string_list_has_string(rr, path)) {
 649                        unsigned char sha1[20];
 650                        char *hex;
 651                        int ret;
 652
 653                        /*
 654                         * Ask handle_file() to scan and assign a
 655                         * conflict ID.  No need to write anything out
 656                         * yet.
 657                         */
 658                        ret = handle_file(path, sha1, NULL);
 659                        if (ret < 1)
 660                                continue;
 661                        hex = xstrdup(sha1_to_hex(sha1));
 662                        string_list_insert(rr, path)->util = hex;
 663
 664                        /*
 665                         * If the directory does not exist, create
 666                         * it.  mkdir_in_gitdir() will fail with
 667                         * EEXIST if there already is one.
 668                         *
 669                         * NEEDSWORK: make sure "gc" does not remove
 670                         * preimage without removing the directory.
 671                         */
 672                        if (mkdir_in_gitdir(git_path("rr-cache/%s", hex)))
 673                                continue;
 674
 675                        /*
 676                         * We are the first to encounter this
 677                         * conflict.  Ask handle_file() to write the
 678                         * normalized contents to the "preimage" file.
 679                         */
 680                        handle_file(path, NULL, rerere_path(hex, "preimage"));
 681                        fprintf(stderr, "Recorded preimage for '%s'\n", path);
 682                }
 683        }
 684
 685        /*
 686         * Some of the paths that had conflicts earlier might have
 687         * been resolved by the user.  Others may be similar to a
 688         * conflict already that was resolved before.
 689         */
 690        for (i = 0; i < rr->nr; i++) {
 691                int ret;
 692                const char *path = rr->items[i].string;
 693                const char *name = (const char *)rr->items[i].util;
 694
 695                /* Is there a recorded resolution we could attempt to apply? */
 696                if (has_rerere_resolution(name)) {
 697                        if (merge(name, path))
 698                                continue;
 699
 700                        if (rerere_autoupdate)
 701                                string_list_insert(&update, path);
 702                        else
 703                                fprintf(stderr,
 704                                        "Resolved '%s' using previous resolution.\n",
 705                                        path);
 706                        goto mark_resolved;
 707                }
 708
 709                /* Let's see if the user has resolved it. */
 710                ret = handle_file(path, NULL, NULL);
 711                if (ret)
 712                        continue;
 713
 714                copy_file(rerere_path(name, "postimage"), path, 0666);
 715                fprintf(stderr, "Recorded resolution for '%s'.\n", path);
 716        mark_resolved:
 717                free(rr->items[i].util);
 718                rr->items[i].util = NULL;
 719        }
 720
 721        if (update.nr)
 722                update_paths(&update);
 723
 724        return write_rr(rr, fd);
 725}
 726
 727static void git_rerere_config(void)
 728{
 729        git_config_get_bool("rerere.enabled", &rerere_enabled);
 730        git_config_get_bool("rerere.autoupdate", &rerere_autoupdate);
 731        git_config(git_default_config, NULL);
 732}
 733
 734static int is_rerere_enabled(void)
 735{
 736        const char *rr_cache;
 737        int rr_cache_exists;
 738
 739        if (!rerere_enabled)
 740                return 0;
 741
 742        rr_cache = git_path("rr-cache");
 743        rr_cache_exists = is_directory(rr_cache);
 744        if (rerere_enabled < 0)
 745                return rr_cache_exists;
 746
 747        if (!rr_cache_exists && mkdir_in_gitdir(rr_cache))
 748                die("Could not create directory %s", rr_cache);
 749        return 1;
 750}
 751
 752int setup_rerere(struct string_list *merge_rr, int flags)
 753{
 754        int fd;
 755
 756        git_rerere_config();
 757        if (!is_rerere_enabled())
 758                return -1;
 759
 760        if (flags & (RERERE_AUTOUPDATE|RERERE_NOAUTOUPDATE))
 761                rerere_autoupdate = !!(flags & RERERE_AUTOUPDATE);
 762        merge_rr_path = git_pathdup("MERGE_RR");
 763        fd = hold_lock_file_for_update(&write_lock, merge_rr_path,
 764                                       LOCK_DIE_ON_ERROR);
 765        read_rr(merge_rr);
 766        return fd;
 767}
 768
 769/*
 770 * The main entry point that is called internally from codepaths that
 771 * perform mergy operations, possibly leaving conflicted index entries
 772 * and working tree files.
 773 */
 774int rerere(int flags)
 775{
 776        struct string_list merge_rr = STRING_LIST_INIT_DUP;
 777        int fd;
 778
 779        fd = setup_rerere(&merge_rr, flags);
 780        if (fd < 0)
 781                return 0;
 782        return do_plain_rerere(&merge_rr, fd);
 783}
 784
 785static int rerere_forget_one_path(const char *path, struct string_list *rr)
 786{
 787        const char *filename;
 788        char *hex;
 789        unsigned char sha1[20];
 790        int ret;
 791        struct string_list_item *item;
 792
 793        /*
 794         * Recreate the original conflict from the stages in the
 795         * index and compute the conflict ID
 796         */
 797        ret = handle_cache(path, sha1, NULL);
 798        if (ret < 1)
 799                return error("Could not parse conflict hunks in '%s'", path);
 800
 801        /* Nuke the recorded resolution for the conflict */
 802        hex = xstrdup(sha1_to_hex(sha1));
 803        filename = rerere_path(hex, "postimage");
 804        if (unlink(filename))
 805                return (errno == ENOENT
 806                        ? error("no remembered resolution for %s", path)
 807                        : error("cannot unlink %s: %s", filename, strerror(errno)));
 808
 809        /*
 810         * Update the preimage so that the user can resolve the
 811         * conflict in the working tree, run us again to record
 812         * the postimage.
 813         */
 814        handle_cache(path, sha1, rerere_path(hex, "preimage"));
 815        fprintf(stderr, "Updated preimage for '%s'\n", path);
 816
 817        /*
 818         * And remember that we can record resolution for this
 819         * conflict when the user is done.
 820         */
 821        item = string_list_insert(rr, path);
 822        free(item->util);
 823        item->util = hex;
 824        fprintf(stderr, "Forgot resolution for %s\n", path);
 825        return 0;
 826}
 827
 828int rerere_forget(struct pathspec *pathspec)
 829{
 830        int i, fd;
 831        struct string_list conflict = STRING_LIST_INIT_DUP;
 832        struct string_list merge_rr = STRING_LIST_INIT_DUP;
 833
 834        if (read_cache() < 0)
 835                return error("Could not read index");
 836
 837        fd = setup_rerere(&merge_rr, RERERE_NOAUTOUPDATE);
 838
 839        /*
 840         * The paths may have been resolved (incorrectly);
 841         * recover the original conflicted state and then
 842         * find the conflicted paths.
 843         */
 844        unmerge_cache(pathspec);
 845        find_conflict(&conflict);
 846        for (i = 0; i < conflict.nr; i++) {
 847                struct string_list_item *it = &conflict.items[i];
 848                if (!match_pathspec(pathspec, it->string,
 849                                    strlen(it->string), 0, NULL, 0))
 850                        continue;
 851                rerere_forget_one_path(it->string, &merge_rr);
 852        }
 853        return write_rr(&merge_rr, fd);
 854}
 855
 856static time_t rerere_created_at(const char *name)
 857{
 858        struct stat st;
 859        return stat(rerere_path(name, "preimage"), &st) ? (time_t) 0 : st.st_mtime;
 860}
 861
 862static time_t rerere_last_used_at(const char *name)
 863{
 864        struct stat st;
 865        return stat(rerere_path(name, "postimage"), &st) ? (time_t) 0 : st.st_mtime;
 866}
 867
 868static void unlink_rr_item(const char *name)
 869{
 870        unlink(rerere_path(name, "thisimage"));
 871        unlink(rerere_path(name, "preimage"));
 872        unlink(rerere_path(name, "postimage"));
 873        rmdir(git_path("rr-cache/%s", name));
 874}
 875
 876void rerere_gc(struct string_list *rr)
 877{
 878        struct string_list to_remove = STRING_LIST_INIT_DUP;
 879        DIR *dir;
 880        struct dirent *e;
 881        int i, cutoff;
 882        time_t now = time(NULL), then;
 883        int cutoff_noresolve = 15;
 884        int cutoff_resolve = 60;
 885
 886        git_config_get_int("gc.rerereresolved", &cutoff_resolve);
 887        git_config_get_int("gc.rerereunresolved", &cutoff_noresolve);
 888        git_config(git_default_config, NULL);
 889        dir = opendir(git_path("rr-cache"));
 890        if (!dir)
 891                die_errno("unable to open rr-cache directory");
 892        while ((e = readdir(dir))) {
 893                if (is_dot_or_dotdot(e->d_name))
 894                        continue;
 895
 896                then = rerere_last_used_at(e->d_name);
 897                if (then) {
 898                        cutoff = cutoff_resolve;
 899                } else {
 900                        then = rerere_created_at(e->d_name);
 901                        if (!then)
 902                                continue;
 903                        cutoff = cutoff_noresolve;
 904                }
 905                if (then < now - cutoff * 86400)
 906                        string_list_append(&to_remove, e->d_name);
 907        }
 908        closedir(dir);
 909        for (i = 0; i < to_remove.nr; i++)
 910                unlink_rr_item(to_remove.items[i].string);
 911        string_list_clear(&to_remove, 0);
 912}
 913
 914void rerere_clear(struct string_list *merge_rr)
 915{
 916        int i;
 917
 918        for (i = 0; i < merge_rr->nr; i++) {
 919                const char *name = (const char *)merge_rr->items[i].util;
 920                if (!has_rerere_resolution(name))
 921                        unlink_rr_item(name);
 922        }
 923        unlink_or_warn(git_path("MERGE_RR"));
 924}