diff.c

   1 /*
   2  * Copyright (C) 2005 Junio C Hamano
   3  */
   4 #include <sys/types.h>
   5 #include <sys/wait.h>
   6 #include <signal.h>
   7 #include <limits.h>
   8 #include "cache.h"
   9 #include "diff.h"
  10 #include "delta.h"
  11
  12 static const char *diff_opts = "-pu";
  13 static unsigned char null_sha1[20] = { 0, };
  14
  15 static const char *external_diff(void)
  16 {
  17         static const char *external_diff_cmd = NULL;
  18         static int done_preparing = 0;
  19
  20         if (done_preparing)
  21                 return external_diff_cmd;
  22
  23         /*
  24          * Default values above are meant to match the
  25          * Linux kernel development style.  Examples of
  26          * alternative styles you can specify via environment
  27          * variables are:
  28          *
  29          * GIT_DIFF_OPTS="-c";
  30          */
  31         if (gitenv("GIT_EXTERNAL_DIFF"))
  32                 external_diff_cmd = gitenv("GIT_EXTERNAL_DIFF");
  33
  34         /* In case external diff fails... */
  35         diff_opts = gitenv("GIT_DIFF_OPTS") ? : diff_opts;
  36
  37         done_preparing = 1;
  38         return external_diff_cmd;
  39 }
  40
  41 /* Help to copy the thing properly quoted for the shell safety.
  42  * any single quote is replaced with '\'', and the caller is
  43  * expected to enclose the result within a single quote pair.
  44  *
  45  * E.g.
  46  *  original     sq_expand     result
  47  *  name     ==> name      ==> 'name'
  48  *  a b      ==> a b       ==> 'a b'
  49  *  a'b      ==> a'\''b    ==> 'a'\''b'
  50  */
  51 static char *sq_expand(const char *src)
  52 {
  53         static char *buf = NULL;
  54         int cnt, c;
  55         const char *cp;
  56         char *bp;
  57
  58         /* count bytes needed to store the quoted string. */
  59         for (cnt = 1, cp = src; *cp; cnt++, cp++)
  60                 if (*cp == '\'')
  61                         cnt += 3;
  62
  63         buf = xmalloc(cnt);
  64         bp = buf;
  65         while ((c = *src++)) {
  66                 if (c != '\'')
  67                         *bp++ = c;
  68                 else {
  69                         bp = strcpy(bp, "'\\''");
  70                         bp += 4;
  71                 }
  72         }
  73         *bp = 0;
  74         return buf;
  75 }
  76
  77 static struct diff_tempfile {
  78         const char *name;
  79         char hex[41];
  80         char mode[10];
  81         char tmp_path[50];
  82 } diff_temp[2];
  83
  84 struct diff_spec {
  85         unsigned char blob_sha1[20];
  86         unsigned short mode;     /* file mode */
  87         unsigned sha1_valid : 1; /* if true, use blob_sha1 and trust mode;
  88                                   * however with a NULL SHA1, read them
  89                                   * from the file system.
  90                                   * if false, use the name and read mode from
  91                                   * the filesystem.
  92                                   */
  93         unsigned file_valid : 1; /* if false the file does not even exist */
  94 };
  95
  96 static void builtin_diff(const char *name_a,
  97                          const char *name_b,
  98                          struct diff_tempfile *temp)
  99 {
 100         int i, next_at;
 101         const char *diff_cmd = "diff -L'%s%s' -L'%s%s'";
 102         const char *diff_arg  = "'%s' '%s'||:"; /* "||:" is to return 0 */
 103         const char *input_name_sq[2];
 104         const char *path0[2];
 105         const char *path1[2];
 106         const char *name_sq[2];
 107         char *cmd;
 108
 109         name_sq[0] = sq_expand(name_a);
 110         name_sq[1] = sq_expand(name_b);
 111
 112         /* diff_cmd and diff_arg have 6 %s in total which makes
 113          * the sum of these strings 12 bytes larger than required.
 114          * we use 2 spaces around diff-opts, and we need to count
 115          * terminating NUL, so we subtract 9 here.
 116          */
 117         int cmd_size = (strlen(diff_cmd) + strlen(diff_opts) +
 118                         strlen(diff_arg) - 9);
 119         for (i = 0; i < 2; i++) {
 120                 input_name_sq[i] = sq_expand(temp[i].name);
 121                 if (!strcmp(temp[i].name, "/dev/null")) {
 122                         path0[i] = "/dev/null";
 123                         path1[i] = "";
 124                 } else {
 125                         path0[i] = i ? "b/" : "a/";
 126                         path1[i] = name_sq[i];
 127                 }
 128                 cmd_size += (strlen(path0[i]) + strlen(path1[i]) +
 129                              strlen(input_name_sq[i]));
 130         }
 131
 132         cmd = xmalloc(cmd_size);
 133
 134         next_at = 0;
 135         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 136                             diff_cmd,
 137                             path0[0], path1[0], path0[1], path1[1]);
 138         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 139                             " %s ", diff_opts);
 140         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 141                             diff_arg, input_name_sq[0], input_name_sq[1]);
 142
 143         printf("diff --git a/%s b/%s\n", name_a, name_b);
 144         if (!path1[0][0])
 145                 printf("new file mode %s\n", temp[1].mode);
 146         else if (!path1[1][0])
 147                 printf("deleted file mode %s\n", temp[0].mode);
 148         else {
 149                 if (strcmp(temp[0].mode, temp[1].mode)) {
 150                         printf("old mode %s\n", temp[0].mode);
 151                         printf("new mode %s\n", temp[1].mode);
 152                 }
 153                 if (strcmp(name_a, name_b)) {
 154                         printf("rename old %s\n", name_a);
 155                         printf("rename new %s\n", name_b);
 156                 }
 157                 if (strncmp(temp[0].mode, temp[1].mode, 3))
 158                         /* we do not run diff between different kind
 159                          * of objects.
 160                          */
 161                         exit(0);
 162         }
 163         fflush(NULL);
 164         execlp("/bin/sh","sh", "-c", cmd, NULL);
 165 }
 166
 167 /*
 168  * Given a name and sha1 pair, if the dircache tells us the file in
 169  * the work tree has that object contents, return true, so that
 170  * prepare_temp_file() does not have to inflate and extract.
 171  */
 172 static int work_tree_matches(const char *name, const unsigned char *sha1)
 173 {
 174         struct cache_entry *ce;
 175         struct stat st;
 176         int pos, len;
 177
 178         /* We do not read the cache ourselves here, because the
 179          * benchmark with my previous version that always reads cache
 180          * shows that it makes things worse for diff-tree comparing
 181          * two linux-2.6 kernel trees in an already checked out work
 182          * tree.  This is because most diff-tree comparisons deal with
 183          * only a small number of files, while reading the cache is
 184          * expensive for a large project, and its cost outweighs the
 185          * savings we get by not inflating the object to a temporary
 186          * file.  Practically, this code only helps when we are used
 187          * by diff-cache --cached, which does read the cache before
 188          * calling us.
 189          */
 190         if (!active_cache)
 191                 return 0;
 192
 193         len = strlen(name);
 194         pos = cache_name_pos(name, len);
 195         if (pos < 0)
 196                 return 0;
 197         ce = active_cache[pos];
 198         if ((lstat(name, &st) < 0) ||
 199             !S_ISREG(st.st_mode) ||
 200             ce_match_stat(ce, &st) ||
 201             memcmp(sha1, ce->sha1, 20))
 202                 return 0;
 203         return 1;
 204 }
 205
 206 static void prep_temp_blob(struct diff_tempfile *temp,
 207                            void *blob,
 208                            unsigned long size,
 209                            unsigned char *sha1,
 210                            int mode)
 211 {
 212         int fd;
 213
 214         strcpy(temp->tmp_path, ".diff_XXXXXX");
 215         fd = mkstemp(temp->tmp_path);
 216         if (fd < 0)
 217                 die("unable to create temp-file");
 218         if (write(fd, blob, size) != size)
 219                 die("unable to write temp-file");
 220         close(fd);
 221         temp->name = temp->tmp_path;
 222         strcpy(temp->hex, sha1_to_hex(sha1));
 223         temp->hex[40] = 0;
 224         sprintf(temp->mode, "%06o", mode);
 225 }
 226
 227 static void prepare_temp_file(const char *name,
 228                               struct diff_tempfile *temp,
 229                               struct diff_spec *one)
 230 {
 231         if (!one->file_valid) {
 232         not_a_valid_file:
 233                 /* A '-' entry produces this for file-2, and
 234                  * a '+' entry produces this for file-1.
 235                  */
 236                 temp->name = "/dev/null";
 237                 strcpy(temp->hex, ".");
 238                 strcpy(temp->mode, ".");
 239                 return;
 240         }
 241
 242         if (!one->sha1_valid ||
 243             work_tree_matches(name, one->blob_sha1)) {
 244                 struct stat st;
 245                 temp->name = name;
 246                 if (lstat(temp->name, &st) < 0) {
 247                         if (errno == ENOENT)
 248                                 goto not_a_valid_file;
 249                         die("stat(%s): %s", temp->name, strerror(errno));
 250                 }
 251                 if (S_ISLNK(st.st_mode)) {
 252                         int ret;
 253                         char *buf, buf_[1024];
 254                         buf = ((sizeof(buf_) < st.st_size) ?
 255                                xmalloc(st.st_size) : buf_);
 256                         ret = readlink(name, buf, st.st_size);
 257                         if (ret < 0)
 258                                 die("readlink(%s)", name);
 259                         prep_temp_blob(temp, buf, st.st_size,
 260                                        (one->sha1_valid ?
 261                                         one->blob_sha1 : null_sha1),
 262                                        (one->sha1_valid ?
 263                                         one->mode : S_IFLNK));
 264                 }
 265                 else {
 266                         if (!one->sha1_valid)
 267                                 strcpy(temp->hex, sha1_to_hex(null_sha1));
 268                         else
 269                                 strcpy(temp->hex, sha1_to_hex(one->blob_sha1));
 270                         sprintf(temp->mode, "%06o",
 271                                 S_IFREG |ce_permissions(st.st_mode));
 272                 }
 273                 return;
 274         }
 275         else {
 276                 void *blob;
 277                 char type[20];
 278                 unsigned long size;
 279
 280                 blob = read_sha1_file(one->blob_sha1, type, &size);
 281                 if (!blob || strcmp(type, "blob"))
 282                         die("unable to read blob object for %s (%s)",
 283                             name, sha1_to_hex(one->blob_sha1));
 284                 prep_temp_blob(temp, blob, size, one->blob_sha1, one->mode);
 285                 free(blob);
 286         }
 287 }
 288
 289 static void remove_tempfile(void)
 290 {
 291         int i;
 292
 293         for (i = 0; i < 2; i++)
 294                 if (diff_temp[i].name == diff_temp[i].tmp_path) {
 295                         unlink(diff_temp[i].name);
 296                         diff_temp[i].name = NULL;
 297                 }
 298 }
 299
 300 static void remove_tempfile_on_signal(int signo)
 301 {
 302         remove_tempfile();
 303 }
 304
 305 static int detect_rename;
 306 static int reverse_diff;
 307 static const char **pathspec;
 308 static int speccnt;
 309 static int diff_rename_minimum_score;
 310
 311 static int matches_pathspec(const char *name)
 312 {
 313         int i;
 314         int namelen;
 315
 316         if (speccnt == 0)
 317                 return 1;
 318
 319         namelen = strlen(name);
 320         for (i = 0; i < speccnt; i++) {
 321                 int speclen = strlen(pathspec[i]);
 322                 if (! strncmp(pathspec[i], name, speclen) &&
 323                     speclen <= namelen &&
 324                     (name[speclen] == 0 || name[speclen] == '/'))
 325                         return 1;
 326         }
 327         return 0;
 328 }
 329
 330 /* An external diff command takes:
 331  *
 332  * diff-cmd name infile1 infile1-sha1 infile1-mode \
 333  *               infile2 infile2-sha1 infile2-mode [ rename-to ]
 334  *
 335  */
 336 static void run_external_diff(const char *name,
 337                               const char *other,
 338                               struct diff_spec *one,
 339                               struct diff_spec *two)
 340 {
 341         struct diff_tempfile *temp = diff_temp;
 342         pid_t pid;
 343         int status;
 344         static int atexit_asked = 0;
 345
 346         if (reverse_diff) {
 347                 struct diff_spec *tmp_spec;
 348                 tmp_spec = one; one = two; two = tmp_spec;
 349                 if (other) {
 350                         const char *tmp;
 351                         tmp = name; name = other; other = tmp;
 352                 }
 353         }
 354
 355         if (!matches_pathspec(name) && (!other || !matches_pathspec(other)))
 356                 return;
 357
 358         if (one && two) {
 359                 prepare_temp_file(name, &temp[0], one);
 360                 prepare_temp_file(other ? : name, &temp[1], two);
 361                 if (! atexit_asked &&
 362                     (temp[0].name == temp[0].tmp_path ||
 363                      temp[1].name == temp[1].tmp_path)) {
 364                         atexit_asked = 1;
 365                         atexit(remove_tempfile);
 366                 }
 367                 signal(SIGINT, remove_tempfile_on_signal);
 368         }
 369
 370         fflush(NULL);
 371         pid = fork();
 372         if (pid < 0)
 373                 die("unable to fork");
 374         if (!pid) {
 375                 const char *pgm = external_diff();
 376                 if (pgm) {
 377                         if (one && two) {
 378                                 const char *exec_arg[9];
 379                                 const char **arg = &exec_arg[0];
 380                                 *arg++ = pgm;
 381                                 *arg++ = name;
 382                                 *arg++ = temp[0].name;
 383                                 *arg++ = temp[0].hex;
 384                                 *arg++ = temp[0].mode;
 385                                 *arg++ = temp[1].name;
 386                                 *arg++ = temp[1].hex;
 387                                 *arg++ = temp[1].mode;
 388                                 if (other)
 389                                         *arg++ = other;
 390                                 *arg = 0;
 391                                 execvp(pgm, (char *const*) exec_arg);
 392                         }
 393                         else
 394                                 execlp(pgm, pgm, name, NULL);
 395                 }
 396                 /*
 397                  * otherwise we use the built-in one.
 398                  */
 399                 if (one && two)
 400                         builtin_diff(name, other ? : name, temp);
 401                 else
 402                         printf("* Unmerged path %s\n", name);
 403                 exit(0);
 404         }
 405         if (waitpid(pid, &status, 0) < 0 ||
 406             !WIFEXITED(status) || WEXITSTATUS(status)) {
 407                 /* Earlier we did not check the exit status because
 408                  * diff exits non-zero if files are different, and
 409                  * we are not interested in knowing that.  It was a
 410                  * mistake which made it harder to quit a diff-*
 411                  * session that uses the git-apply-patch-script as
 412                  * the GIT_EXTERNAL_DIFF.  A custom GIT_EXTERNAL_DIFF
 413                  * should also exit non-zero only when it wants to
 414                  * abort the entire diff-* session.
 415                  */
 416                 remove_tempfile();
 417                 fprintf(stderr, "external diff died, stopping at %s.\n", name);
 418                 exit(1);
 419         }
 420         remove_tempfile();
 421 }
 422
 423 /*
 424  * We do not detect circular renames.  Just hold created and deleted
 425  * entries and later attempt to match them up.  If they do not match,
 426  * then spit them out as deletes or creates as original.
 427  */
 428
 429 static struct diff_spec_hold {
 430         struct diff_spec_hold *next;
 431         struct diff_spec it;
 432         unsigned long size;
 433         int flags;
 434 #define MATCHED 1
 435 #define SHOULD_FREE 2
 436 #define SHOULD_MUNMAP 4
 437         void *data;
 438         char path[1];
 439 } *createdfile, *deletedfile;
 440
 441 static void hold_diff(const char *name,
 442                       struct diff_spec *one,
 443                       struct diff_spec *two)
 444 {
 445         struct diff_spec_hold **list, *elem;
 446
 447         if (one->file_valid && two->file_valid)
 448                 die("internal error");
 449
 450         if (!detect_rename) {
 451                 run_external_diff(name, NULL, one, two);
 452                 return;
 453         }
 454         elem = xmalloc(sizeof(*elem) + strlen(name));
 455         strcpy(elem->path, name);
 456         elem->size = 0;
 457         elem->data = NULL;
 458         elem->flags = 0;
 459         if (one->file_valid) {
 460                 list = &deletedfile;
 461                 elem->it = *one;
 462         }
 463         else {
 464                 list = &createdfile;
 465                 elem->it = *two;
 466         }
 467         elem->next = *list;
 468         *list = elem;
 469 }
 470
 471 static int populate_data(struct diff_spec_hold *s)
 472 {
 473         char type[20];
 474
 475         if (s->data)
 476                 return 0;
 477         if (s->it.sha1_valid) {
 478                 s->data = read_sha1_file(s->it.blob_sha1, type, &s->size);
 479                 s->flags |= SHOULD_FREE;
 480         }
 481         else {
 482                 struct stat st;
 483                 int fd;
 484                 fd = open(s->path, O_RDONLY);
 485                 if (fd < 0)
 486                         return -1;
 487                 if (fstat(fd, &st)) {
 488                         close(fd);
 489                         return -1;
 490                 }
 491                 s->size = st.st_size;
 492                 s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
 493                 close(fd);
 494                 if (!s->size)
 495                         s->data = "";
 496                 else
 497                         s->flags |= SHOULD_MUNMAP;
 498         }
 499         return 0;
 500 }
 501
 502 static void free_data(struct diff_spec_hold *s)
 503 {
 504         if (s->flags & SHOULD_FREE)
 505                 free(s->data);
 506         else if (s->flags & SHOULD_MUNMAP)
 507                 munmap(s->data, s->size);
 508         s->flags &= ~(SHOULD_FREE|SHOULD_MUNMAP);
 509 }
 510
 511 static void flush_remaining_diff(struct diff_spec_hold *elem,
 512                                  int on_created_list)
 513 {
 514         static struct diff_spec null_file_spec;
 515
 516         null_file_spec.file_valid = 0;
 517         for ( ; elem ; elem = elem->next) {
 518                 free_data(elem);
 519                 if (elem->flags & MATCHED)
 520                         continue;
 521                 if (on_created_list)
 522                         run_external_diff(elem->path, NULL,
 523                                           &null_file_spec, &elem->it);
 524                 else
 525                         run_external_diff(elem->path, NULL,
 526                                           &elem->it, &null_file_spec);
 527         }
 528 }
 529
 530 static int is_exact_match(struct diff_spec_hold *src,
 531                           struct diff_spec_hold *dst)
 532 {
 533         if (src->it.sha1_valid && dst->it.sha1_valid &&
 534             !memcmp(src->it.blob_sha1, dst->it.blob_sha1, 20))
 535                 return 1;
 536         if (populate_data(src) || populate_data(dst))
 537                 /* this is an error but will be caught downstream */
 538                 return 0;
 539         if (src->size == dst->size &&
 540             !memcmp(src->data, dst->data, src->size))
 541                 return 1;
 542         return 0;
 543 }
 544
 545 #define MINIMUM_SCORE 5000
 546 int estimate_similarity(struct diff_spec_hold *src, struct diff_spec_hold *dst)
 547 {
 548         /* src points at a deleted file and dst points at a created
 549          * file.  They may be quite similar, in which case we want to
 550          * say src is renamed to dst.
 551          *
 552          * Compare them and return how similar they are, representing
 553          * the score as an integer between 0 and 10000.  10000 is
 554          * reserved for the case where they match exactly.
 555          */
 556         void *delta;
 557         unsigned long delta_size;
 558
 559         delta_size = ((src->size < dst->size) ?
 560                       (dst->size - src->size) : (src->size - dst->size));
 561
 562         /* We would not consider rename followed by more than
 563          * 20% edits; that is, delta_size must be smaller than
 564          * (src->size + dst->size)/2 * 0.2, which means...
 565          */
 566         if ((src->size + dst->size) < delta_size * 10)
 567                 return 0;
 568
 569         delta = diff_delta(src->data, src->size,
 570                            dst->data, dst->size,
 571                            &delta_size);
 572         free(delta);
 573
 574         /* This "delta" is really xdiff with adler32 and all the
 575          * overheads but it is a quick and dirty approximation.
 576          *
 577          * Now we will give some score to it.  Let's say 20% edit gets
 578          * 5000 points and 0% edit gets 9000 points.  That is, every
 579          * 1/20000 edit gets 1 point penalty.  The amount of penalty is:
 580          *
 581          * (delta_size * 2 / (src->size + dst->size)) * 20000
 582          *
 583          */
 584         return 9000 - (40000 * delta_size / (src->size+dst->size));
 585 }
 586
 587 struct diff_score {
 588         struct diff_spec_hold *src;
 589         struct diff_spec_hold *dst;
 590         int score;
 591 };
 592
 593 static int score_compare(const void *a_, const void *b_)
 594 {
 595         const struct diff_score *a = a_, *b = b_;
 596         return b->score - a->score;
 597 }
 598
 599 static void flush_rename_pair(struct diff_spec_hold *src,
 600                               struct diff_spec_hold *dst)
 601 {
 602         src->flags |= MATCHED;
 603         dst->flags |= MATCHED;
 604         free_data(src);
 605         free_data(dst);
 606         run_external_diff(src->path, dst->path,
 607                           &src->it, &dst->it);
 608 }
 609
 610 static void free_held_diff(struct diff_spec_hold *list)
 611 {
 612         struct diff_spec_hold *h;
 613         for (h = list; list; list = h) {
 614                 h = list->next;
 615                 free_data(list);
 616                 free(list);
 617         }
 618 }
 619
 620 void diff_flush(void)
 621 {
 622         int num_create, num_delete, c, d;
 623         struct diff_spec_hold *elem, *src, *dst;
 624         struct diff_score *mx;
 625
 626         /* We really want to cull the candidates list early
 627          * with cheap tests in order to avoid doing deltas.
 628          */
 629         for (dst = createdfile; dst; dst = dst->next) {
 630                 for (src = deletedfile; src; src = src->next) {
 631                         if (! is_exact_match(src, dst))
 632                                 continue;
 633                         flush_rename_pair(src, dst);
 634                         break;
 635                 }
 636         }
 637
 638         /* Count surviving candidates */
 639         for (num_create = 0, elem = createdfile; elem; elem = elem->next)
 640                 if (!(elem->flags & MATCHED))
 641                         num_create++;
 642
 643         for (num_delete = 0, elem = deletedfile; elem; elem = elem->next)
 644                 if (!(elem->flags & MATCHED))
 645                         num_delete++;
 646
 647         if (num_create == 0 ||  num_delete == 0)
 648                 goto exit_path;
 649
 650         mx = xmalloc(sizeof(*mx) * num_create * num_delete);
 651         for (c = 0, dst = createdfile; dst; dst = dst->next) {
 652                 int base = c * num_delete;
 653                 if (dst->flags & MATCHED)
 654                         continue;
 655                 for (d = 0, src = deletedfile; src; src = src->next) {
 656                         struct diff_score *m = &mx[base+d];
 657                         if (src->flags & MATCHED)
 658                                 continue;
 659                         m->src = src;
 660                         m->dst = dst;
 661                         m->score = estimate_similarity(src, dst);
 662                         d++;
 663                 }
 664                 c++;
 665         }
 666         qsort(mx, num_create*num_delete, sizeof(*mx), score_compare);
 667
 668         for (c = 0; c < num_create * num_delete; c++) {
 669                 src = mx[c].src;
 670                 dst = mx[c].dst;
 671                 if ((src->flags & MATCHED) || (dst->flags & MATCHED))
 672                         continue;
 673         }
 674
 675         for (c = 0; c < num_create * num_delete; c++) {
 676                 src = mx[c].src;
 677                 dst = mx[c].dst;
 678                 if ((src->flags & MATCHED) || (dst->flags & MATCHED))
 679                         continue;
 680                 if (mx[c].score < diff_rename_minimum_score)
 681                         break;
 682                 flush_rename_pair(src, dst);
 683         }
 684
 685  exit_path:
 686         flush_remaining_diff(createdfile, 1);
 687         flush_remaining_diff(deletedfile, 0);
 688         free_held_diff(createdfile);
 689         free_held_diff(deletedfile);
 690         createdfile = deletedfile = NULL;
 691 }
 692
 693 void diff_setup(int detect_rename_, int minimum_score_, int reverse_diff_,
 694                 const char **pathspec_, int speccnt_)
 695 {
 696         free_held_diff(createdfile);
 697         free_held_diff(deletedfile);
 698         createdfile = deletedfile = NULL;
 699
 700         detect_rename = detect_rename_;
 701         reverse_diff = reverse_diff_;
 702         pathspec = pathspec_;
 703         speccnt = speccnt_;
 704         diff_rename_minimum_score = minimum_score_ ? : MINIMUM_SCORE;
 705 }
 706
 707 void diff_addremove(int addremove, unsigned mode,
 708                     const unsigned char *sha1,
 709                     const char *base, const char *path)
 710 {
 711         char concatpath[PATH_MAX];
 712         struct diff_spec spec[2], *one, *two;
 713
 714         memcpy(spec[0].blob_sha1, sha1, 20);
 715         spec[0].mode = mode;
 716         spec[0].sha1_valid = !!memcmp(sha1, null_sha1, 20);
 717         spec[0].file_valid = 1;
 718         spec[1].file_valid = 0;
 719
 720         if (addremove == '+') {
 721                 one = spec + 1; two = spec;
 722         } else {
 723                 one = spec; two = one + 1;
 724         }
 725
 726         if (path) {
 727                 strcpy(concatpath, base);
 728                 strcat(concatpath, path);
 729         }
 730         hold_diff(path ? concatpath : base, one, two);
 731 }
 732
 733 void diff_change(unsigned old_mode, unsigned new_mode,
 734                  const unsigned char *old_sha1,
 735                  const unsigned char *new_sha1,
 736                  const char *base, const char *path) {
 737         char concatpath[PATH_MAX];
 738         struct diff_spec spec[2];
 739
 740         if (path) {
 741                 strcpy(concatpath, base);
 742                 strcat(concatpath, path);
 743         }
 744
 745         memcpy(spec[0].blob_sha1, old_sha1, 20);
 746         spec[0].mode = old_mode;
 747         memcpy(spec[1].blob_sha1, new_sha1, 20);
 748         spec[1].mode = new_mode;
 749         spec[0].sha1_valid = !!memcmp(old_sha1, null_sha1, 20);
 750         spec[1].sha1_valid = !!memcmp(new_sha1, null_sha1, 20);
 751         spec[1].file_valid = spec[0].file_valid = 1;
 752
 753         /* We do not look at changed files as candidate for
 754          * rename detection ever.
 755          */
 756         run_external_diff(path ? concatpath : base, NULL, &spec[0], &spec[1]);
 757 }
 758
 759 void diff_unmerge(const char *path)
 760 {
 761         run_external_diff(path, NULL, NULL, NULL);
 762 }