combine-diff.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "diff.h"
   4 #include "diffcore.h"
   5 #include "quote.h"
   6
   7 static int uninteresting(struct diff_filepair *p)
   8 {
   9         if (diff_unmodified_pair(p))
  10                 return 1;
  11         if (!S_ISREG(p->one->mode) || !S_ISREG(p->two->mode))
  12                 return 1;
  13         return 0;
  14 }
  15
  16 static struct combine_diff_path *intersect_paths(struct combine_diff_path *curr, int n, int num_parent)
  17 {
  18         struct diff_queue_struct *q = &diff_queued_diff;
  19         struct combine_diff_path *p;
  20         int i;
  21
  22         if (!n) {
  23                 struct combine_diff_path *list = NULL, **tail = &list;
  24                 for (i = 0; i < q->nr; i++) {
  25                         int len;
  26                         const char *path;
  27                         if (uninteresting(q->queue[i]))
  28                                 continue;
  29                         path = q->queue[i]->two->path;
  30                         len = strlen(path);
  31                         p = xmalloc(combine_diff_path_size(num_parent, len));
  32                         p->path = (char*) &(p->parent[num_parent]);
  33                         memcpy(p->path, path, len);
  34                         p->path[len] = 0;
  35                         p->len = len;
  36                         p->next = NULL;
  37                         memset(p->parent, 0,
  38                                sizeof(p->parent[0]) * num_parent);
  39
  40                         memcpy(p->sha1, q->queue[i]->two->sha1, 20);
  41                         p->mode = q->queue[i]->two->mode;
  42                         memcpy(p->parent[n].sha1, q->queue[i]->one->sha1, 20);
  43                         p->parent[n].mode = q->queue[i]->one->mode;
  44                         *tail = p;
  45                         tail = &p->next;
  46                 }
  47                 return list;
  48         }
  49
  50         for (p = curr; p; p = p->next) {
  51                 int found = 0;
  52                 if (!p->len)
  53                         continue;
  54                 for (i = 0; i < q->nr; i++) {
  55                         const char *path;
  56                         int len;
  57
  58                         if (uninteresting(q->queue[i]))
  59                                 continue;
  60                         path = q->queue[i]->two->path;
  61                         len = strlen(path);
  62                         if (len == p->len && !memcmp(path, p->path, len)) {
  63                                 found = 1;
  64                                 memcpy(p->parent[n].sha1,
  65                                        q->queue[i]->one->sha1, 20);
  66                                 p->parent[n].mode = q->queue[i]->one->mode;
  67                                 break;
  68                         }
  69                 }
  70                 if (!found)
  71                         p->len = 0;
  72         }
  73         return curr;
  74 }
  75
  76 /* Lines lost from parent */
  77 struct lline {
  78         struct lline *next;
  79         int len;
  80         unsigned long parent_map;
  81         char line[FLEX_ARRAY];
  82 };
  83
  84 /* Lines surviving in the merge result */
  85 struct sline {
  86         struct lline *lost_head, **lost_tail;
  87         char *bol;
  88         int len;
  89         /* bit 0 up to (N-1) are on if the parent has this line (i.e.
  90          * we did not change it).
  91          * bit N is used for "interesting" lines, including context.
  92          */
  93         unsigned long flag;
  94         unsigned long *p_lno;
  95 };
  96
  97 static char *grab_blob(const unsigned char *sha1, unsigned long *size)
  98 {
  99         char *blob;
 100         char type[20];
 101         if (!memcmp(sha1, null_sha1, 20)) {
 102                 /* deleted blob */
 103                 *size = 0;
 104                 return xcalloc(1, 1);
 105         }
 106         blob = read_sha1_file(sha1, type, size);
 107         if (strcmp(type, "blob"))
 108                 die("object '%s' is not a blob!", sha1_to_hex(sha1));
 109         return blob;
 110 }
 111
 112 #define TMPPATHLEN 50
 113 #define MAXLINELEN 10240
 114
 115 static void write_to_temp_file(char *tmpfile, void *blob, unsigned long size)
 116 {
 117         int fd = git_mkstemp(tmpfile, TMPPATHLEN, ".diff_XXXXXX");
 118         if (fd < 0)
 119                 die("unable to create temp-file");
 120         if (write(fd, blob, size) != size)
 121                 die("unable to write temp-file");
 122         close(fd);
 123 }
 124
 125 static void write_temp_blob(char *tmpfile, const unsigned char *sha1)
 126 {
 127         unsigned long size;
 128         void *blob;
 129         blob = grab_blob(sha1, &size);
 130         write_to_temp_file(tmpfile, blob, size);
 131         free(blob);
 132 }
 133
 134 static int parse_num(char **cp_p, unsigned int *num_p)
 135 {
 136         char *cp = *cp_p;
 137         unsigned int num = 0;
 138         int read_some;
 139
 140         while ('0' <= *cp && *cp <= '9')
 141                 num = num * 10 + *cp++ - '0';
 142         if (!(read_some = cp - *cp_p))
 143                 return -1;
 144         *cp_p = cp;
 145         *num_p = num;
 146         return 0;
 147 }
 148
 149 static int parse_hunk_header(char *line, int len,
 150                              unsigned int *ob, unsigned int *on,
 151                              unsigned int *nb, unsigned int *nn)
 152 {
 153         char *cp;
 154         cp = line + 4;
 155         if (parse_num(&cp, ob)) {
 156         bad_line:
 157                 return error("malformed diff output: %s", line);
 158         }
 159         if (*cp == ',') {
 160                 cp++;
 161                 if (parse_num(&cp, on))
 162                         goto bad_line;
 163         }
 164         else
 165                 *on = 1;
 166         if (*cp++ != ' ' || *cp++ != '+')
 167                 goto bad_line;
 168         if (parse_num(&cp, nb))
 169                 goto bad_line;
 170         if (*cp == ',') {
 171                 cp++;
 172                 if (parse_num(&cp, nn))
 173                         goto bad_line;
 174         }
 175         else
 176                 *nn = 1;
 177         return -!!memcmp(cp, " @@", 3);
 178 }
 179
 180 static void append_lost(struct sline *sline, int n, const char *line)
 181 {
 182         struct lline *lline;
 183         int len = strlen(line);
 184         unsigned long this_mask = (1UL<<n);
 185         if (line[len-1] == '\n')
 186                 len--;
 187
 188         /* Check to see if we can squash things */
 189         if (sline->lost_head) {
 190                 struct lline *last_one = NULL;
 191                 /* We cannot squash it with earlier one */
 192                 for (lline = sline->lost_head;
 193                      lline;
 194                      lline = lline->next)
 195                         if (lline->parent_map & this_mask)
 196                                 last_one = lline;
 197                 lline = last_one ? last_one->next : sline->lost_head;
 198                 while (lline) {
 199                         if (lline->len == len &&
 200                             !memcmp(lline->line, line, len)) {
 201                                 lline->parent_map |= this_mask;
 202                                 return;
 203                         }
 204                         lline = lline->next;
 205                 }
 206         }
 207
 208         lline = xmalloc(sizeof(*lline) + len + 1);
 209         lline->len = len;
 210         lline->next = NULL;
 211         lline->parent_map = this_mask;
 212         memcpy(lline->line, line, len);
 213         lline->line[len] = 0;
 214         *sline->lost_tail = lline;
 215         sline->lost_tail = &lline->next;
 216 }
 217
 218 static void combine_diff(const unsigned char *parent, const char *ourtmp,
 219                          struct sline *sline, int cnt, int n, int num_parent)
 220 {
 221         FILE *in;
 222         char parent_tmp[TMPPATHLEN];
 223         char cmd[TMPPATHLEN * 2 + 1024];
 224         char line[MAXLINELEN];
 225         unsigned int lno, ob, on, nb, nn, p_lno;
 226         unsigned long nmask = (1UL << n);
 227         struct sline *lost_bucket = NULL;
 228
 229         write_temp_blob(parent_tmp, parent);
 230         sprintf(cmd, "diff --unified=0 -La/x -Lb/x '%s' '%s'",
 231                 parent_tmp, ourtmp);
 232         in = popen(cmd, "r");
 233         if (!in)
 234                 die("cannot spawn %s", cmd);
 235
 236         lno = 1;
 237         while (fgets(line, sizeof(line), in) != NULL) {
 238                 int len = strlen(line);
 239                 if (5 < len && !memcmp("@@ -", line, 4)) {
 240                         if (parse_hunk_header(line, len,
 241                                               &ob, &on, &nb, &nn))
 242                                 break;
 243                         lno = nb;
 244                         if (!nb)
 245                                 /* @@ -1,2 +0,0 @@ to remove the
 246                                  * first two lines...
 247                                  */
 248                                 nb = 1;
 249                         if (nn == 0)
 250                                 /* @@ -X,Y +N,0 @@ removed Y lines
 251                                  * that would have come *after* line N
 252                                  * in the result.  Our lost buckets hang
 253                                  * to the line after the removed lines,
 254                                  */
 255                                 lost_bucket = &sline[nb];
 256                         else
 257                                 lost_bucket = &sline[nb-1];
 258                         if (!sline[nb-1].p_lno)
 259                                 sline[nb-1].p_lno =
 260                                         xcalloc(num_parent,
 261                                                 sizeof(unsigned long));
 262                         sline[nb-1].p_lno[n] = ob;
 263                         continue;
 264                 }
 265                 if (!lost_bucket)
 266                         continue; /* not in any hunk yet */
 267                 switch (line[0]) {
 268                 case '-':
 269                         append_lost(lost_bucket, n, line+1);
 270                         break;
 271                 case '+':
 272                         sline[lno-1].flag |= nmask;
 273                         lno++;
 274                         break;
 275                 }
 276         }
 277         fclose(in);
 278         unlink(parent_tmp);
 279
 280         /* Assign line numbers for this parent.
 281          *
 282          * sline[lno].p_lno[n] records the first line number
 283          * (counting from 1) for parent N if the final hunk display
 284          * started by showing sline[lno] (possibly showing the lost
 285          * lines attached to it first).
 286          */
 287         for (lno = 0,  p_lno = 1; lno < cnt; lno++) {
 288                 struct lline *ll;
 289                 sline[lno].p_lno[n] = p_lno;
 290
 291                 /* How many lines would this sline advance the p_lno? */
 292                 ll = sline[lno].lost_head;
 293                 while (ll) {
 294                         if (ll->parent_map & nmask)
 295                                 p_lno++; /* '-' means parent had it */
 296                         ll = ll->next;
 297                 }
 298                 if (!(sline[lno].flag & nmask))
 299                         p_lno++; /* no '+' means parent had it */
 300         }
 301         sline[lno].p_lno[n] = p_lno; /* trailer */
 302 }
 303
 304 static unsigned long context = 3;
 305 static char combine_marker = '@';
 306
 307 static int interesting(struct sline *sline, unsigned long all_mask)
 308 {
 309         /* If some parents lost lines here, or if we have added to
 310          * some parent, it is interesting.
 311          */
 312         return ((sline->flag & all_mask) || sline->lost_head);
 313 }
 314
 315 static unsigned long adjust_hunk_tail(struct sline *sline,
 316                                       unsigned long all_mask,
 317                                       unsigned long hunk_begin,
 318                                       unsigned long i)
 319 {
 320         /* i points at the first uninteresting line.  If the last line
 321          * of the hunk was interesting only because it has some
 322          * deletion, then it is not all that interesting for the
 323          * purpose of giving trailing context lines.  This is because
 324          * we output '-' line and then unmodified sline[i-1] itself in
 325          * that case which gives us one extra context line.
 326          */
 327         if ((hunk_begin + 1 <= i) && !(sline[i-1].flag & all_mask))
 328                 i--;
 329         return i;
 330 }
 331
 332 static unsigned long find_next(struct sline *sline,
 333                                unsigned long mark,
 334                                unsigned long i,
 335                                unsigned long cnt,
 336                                int uninteresting)
 337 {
 338         /* We have examined up to i-1 and are about to look at i.
 339          * Find next interesting or uninteresting line.  Here,
 340          * "interesting" does not mean interesting(), but marked by
 341          * the give_context() function below (i.e. it includes context
 342          * lines that are not interesting to interesting() function
 343          * that are surrounded by interesting() ones.
 344          */
 345         while (i < cnt)
 346                 if (uninteresting
 347                     ? !(sline[i].flag & mark)
 348                     : (sline[i].flag & mark))
 349                         return i;
 350                 else
 351                         i++;
 352         return cnt;
 353 }
 354
 355 static int give_context(struct sline *sline, unsigned long cnt, int num_parent)
 356 {
 357         unsigned long all_mask = (1UL<<num_parent) - 1;
 358         unsigned long mark = (1UL<<num_parent);
 359         unsigned long i;
 360
 361         /* Two groups of interesting lines may have a short gap of
 362          * unintersting lines.  Connect such groups to give them a
 363          * bit of context.
 364          *
 365          * We first start from what the interesting() function says,
 366          * and mark them with "mark", and paint context lines with the
 367          * mark.  So interesting() would still say false for such context
 368          * lines but they are treated as "interesting" in the end.
 369          */
 370         i = find_next(sline, mark, 0, cnt, 0);
 371         if (cnt <= i)
 372                 return 0;
 373
 374         while (i < cnt) {
 375                 unsigned long j = (context < i) ? (i - context) : 0;
 376                 unsigned long k;
 377
 378                 /* Paint a few lines before the first interesting line. */
 379                 while (j < i)
 380                         sline[j++].flag |= mark;
 381
 382         again:
 383                 /* we know up to i is to be included.  where does the
 384                  * next uninteresting one start?
 385                  */
 386                 j = find_next(sline, mark, i, cnt, 1);
 387                 if (cnt <= j)
 388                         break; /* the rest are all interesting */
 389
 390                 /* lookahead context lines */
 391                 k = find_next(sline, mark, j, cnt, 0);
 392                 j = adjust_hunk_tail(sline, all_mask, i, j);
 393
 394                 if (k < j + context) {
 395                         /* k is interesting and [j,k) are not, but
 396                          * paint them interesting because the gap is small.
 397                          */
 398                         while (j < k)
 399                                 sline[j++].flag |= mark;
 400                         i = k;
 401                         goto again;
 402                 }
 403
 404                 /* j is the first uninteresting line and there is
 405                  * no overlap beyond it within context lines.  Paint
 406                  * the trailing edge a bit.
 407                  */
 408                 i = k;
 409                 k = (j + context < cnt) ? j + context : cnt;
 410                 while (j < k)
 411                         sline[j++].flag |= mark;
 412         }
 413         return 1;
 414 }
 415
 416 static int make_hunks(struct sline *sline, unsigned long cnt,
 417                        int num_parent, int dense)
 418 {
 419         unsigned long all_mask = (1UL<<num_parent) - 1;
 420         unsigned long mark = (1UL<<num_parent);
 421         unsigned long i;
 422         int has_interesting = 0;
 423
 424         for (i = 0; i < cnt; i++) {
 425                 if (interesting(&sline[i], all_mask))
 426                         sline[i].flag |= mark;
 427                 else
 428                         sline[i].flag &= ~mark;
 429         }
 430         if (!dense)
 431                 return give_context(sline, cnt, num_parent);
 432
 433         /* Look at each hunk, and if we have changes from only one
 434          * parent, or the changes are the same from all but one
 435          * parent, mark that uninteresting.
 436          */
 437         i = 0;
 438         while (i < cnt) {
 439                 unsigned long j, hunk_begin, hunk_end;
 440                 unsigned long same_diff;
 441                 while (i < cnt && !(sline[i].flag & mark))
 442                         i++;
 443                 if (cnt <= i)
 444                         break; /* No more interesting hunks */
 445                 hunk_begin = i;
 446                 for (j = i + 1; j < cnt; j++) {
 447                         if (!(sline[j].flag & mark)) {
 448                                 /* Look beyond the end to see if there
 449                                  * is an interesting line after this
 450                                  * hunk within context span.
 451                                  */
 452                                 unsigned long la; /* lookahead */
 453                                 int contin = 0;
 454                                 la = adjust_hunk_tail(sline, all_mask,
 455                                                      hunk_begin, j);
 456                                 la = (la + context < cnt) ?
 457                                         (la + context) : cnt;
 458                                 while (j <= --la) {
 459                                         if (sline[la].flag & mark) {
 460                                                 contin = 1;
 461                                                 break;
 462                                         }
 463                                 }
 464                                 if (!contin)
 465                                         break;
 466                                 j = la;
 467                         }
 468                 }
 469                 hunk_end = j;
 470
 471                 /* [i..hunk_end) are interesting.  Now is it really
 472                  * interesting?  We check if there are only two versions
 473                  * and the result matches one of them.  That is, we look
 474                  * at:
 475                  *   (+) line, which records lines added to which parents;
 476                  *       this line appears in the result.
 477                  *   (-) line, which records from what parents the line
 478                  *       was removed; this line does not appear in the result.
 479                  * then check the set of parents the result has difference
 480                  * from, from all lines.  If there are lines that has
 481                  * different set of parents that the result has differences
 482                  * from, that means we have more than two versions.
 483                  *
 484                  * Even when we have only two versions, if the result does
 485                  * not match any of the parents, the it should be considered
 486                  * interesting.  In such a case, we would have all '+' line.
 487                  * After passing the above "two versions" test, that would
 488                  * appear as "the same set of parents" to be "all parents".
 489                  */
 490                 same_diff = 0;
 491                 has_interesting = 0;
 492                 for (j = i; j < hunk_end && !has_interesting; j++) {
 493                         unsigned long this_diff = sline[j].flag & all_mask;
 494                         struct lline *ll = sline[j].lost_head;
 495                         if (this_diff) {
 496                                 /* This has some changes.  Is it the
 497                                  * same as others?
 498                                  */
 499                                 if (!same_diff)
 500                                         same_diff = this_diff;
 501                                 else if (same_diff != this_diff) {
 502                                         has_interesting = 1;
 503                                         break;
 504                                 }
 505                         }
 506                         while (ll && !has_interesting) {
 507                                 /* Lost this line from these parents;
 508                                  * who are they?  Are they the same?
 509                                  */
 510                                 this_diff = ll->parent_map;
 511                                 if (!same_diff)
 512                                         same_diff = this_diff;
 513                                 else if (same_diff != this_diff) {
 514                                         has_interesting = 1;
 515                                 }
 516                                 ll = ll->next;
 517                         }
 518                 }
 519
 520                 if (!has_interesting && same_diff != all_mask) {
 521                         /* This hunk is not that interesting after all */
 522                         for (j = hunk_begin; j < hunk_end; j++)
 523                                 sline[j].flag &= ~mark;
 524                 }
 525                 i = hunk_end;
 526         }
 527
 528         has_interesting = give_context(sline, cnt, num_parent);
 529         return has_interesting;
 530 }
 531
 532 static void show_parent_lno(struct sline *sline, unsigned long l0, unsigned long l1, unsigned long cnt, int n)
 533 {
 534         l0 = sline[l0].p_lno[n];
 535         l1 = sline[l1].p_lno[n];
 536         printf(" -%lu,%lu", l0, l1-l0);
 537 }
 538
 539 static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent)
 540 {
 541         unsigned long mark = (1UL<<num_parent);
 542         int i;
 543         unsigned long lno = 0;
 544
 545         while (1) {
 546                 struct sline *sl = &sline[lno];
 547                 int hunk_end;
 548                 while (lno < cnt && !(sline[lno].flag & mark))
 549                         lno++;
 550                 if (cnt <= lno)
 551                         break;
 552                 for (hunk_end = lno + 1; hunk_end < cnt; hunk_end++)
 553                         if (!(sline[hunk_end].flag & mark))
 554                                 break;
 555                 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
 556                 for (i = 0; i < num_parent; i++)
 557                         show_parent_lno(sline, lno, hunk_end, cnt, i);
 558                 printf(" +%lu,%lu ", lno+1, hunk_end-lno);
 559                 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
 560                 putchar('\n');
 561                 while (lno < hunk_end) {
 562                         struct lline *ll;
 563                         int j;
 564                         unsigned long p_mask;
 565                         sl = &sline[lno++];
 566                         ll = sl->lost_head;
 567                         while (ll) {
 568                                 for (j = 0; j < num_parent; j++) {
 569                                         if (ll->parent_map & (1UL<<j))
 570                                                 putchar('-');
 571                                         else
 572                                                 putchar(' ');
 573                                 }
 574                                 puts(ll->line);
 575                                 ll = ll->next;
 576                         }
 577                         p_mask = 1;
 578                         for (j = 0; j < num_parent; j++) {
 579                                 if (p_mask & sl->flag)
 580                                         putchar('+');
 581                                 else
 582                                         putchar(' ');
 583                                 p_mask <<= 1;
 584                         }
 585                         printf("%.*s\n", sl->len, sl->bol);
 586                 }
 587         }
 588 }
 589
 590 static void reuse_combine_diff(struct sline *sline, unsigned long cnt,
 591                                int i, int j)
 592 {
 593         /* We have already examined parent j and we know parent i
 594          * and parent j are the same, so reuse the combined result
 595          * of parent j for parent i.
 596          */
 597         unsigned long lno, imask, jmask;
 598         imask = (1UL<<i);
 599         jmask = (1UL<<j);
 600
 601         for (lno = 0; lno < cnt; lno++) {
 602                 struct lline *ll = sline->lost_head;
 603                 sline->p_lno[i] = sline->p_lno[j];
 604                 while (ll) {
 605                         if (ll->parent_map & jmask)
 606                                 ll->parent_map |= imask;
 607                         ll = ll->next;
 608                 }
 609                 if (sline->flag & jmask)
 610                         sline->flag |= imask;
 611                 sline++;
 612         }
 613 }
 614
 615 int show_combined_diff(struct combine_diff_path *elem, int num_parent,
 616                        int dense, const char *header)
 617 {
 618         unsigned long size, cnt, lno;
 619         char *result, *cp, *ep;
 620         struct sline *sline; /* survived lines */
 621         int mode_differs = 0;
 622         int i, show_hunks, shown_header = 0;
 623         char ourtmp_buf[TMPPATHLEN];
 624         char *ourtmp = ourtmp_buf;
 625
 626         /* Read the result of merge first */
 627         if (memcmp(elem->sha1, null_sha1, 20)) {
 628                 result = grab_blob(elem->sha1, &size);
 629                 write_to_temp_file(ourtmp, result, size);
 630         }
 631         else {
 632                 /* Used by diff-tree to read from the working tree */
 633                 struct stat st;
 634                 int fd;
 635                 ourtmp = elem->path;
 636                 if (0 <= (fd = open(ourtmp, O_RDONLY)) &&
 637                     !fstat(fd, &st)) {
 638                         int len = st.st_size;
 639                         int cnt = 0;
 640
 641                         size = len;
 642                         result = xmalloc(len + 1);
 643                         while (cnt < len) {
 644                                 int done = xread(fd, result+cnt, len-cnt);
 645                                 if (done == 0)
 646                                         break;
 647                                 if (done < 0)
 648                                         die("read error '%s'", ourtmp);
 649                                 cnt += done;
 650                         }
 651                         result[len] = 0;
 652                 }
 653                 else {
 654                         /* deleted file */
 655                         size = 0;
 656                         result = xmalloc(1);
 657                         result[0] = 0;
 658                         ourtmp = "/dev/null";
 659                 }
 660                 if (0 <= fd)
 661                         close(fd);
 662         }
 663
 664         for (cnt = 0, cp = result; cp - result < size; cp++) {
 665                 if (*cp == '\n')
 666                         cnt++;
 667         }
 668         if (result[size-1] != '\n')
 669                 cnt++; /* incomplete line */
 670
 671         sline = xcalloc(cnt+1, sizeof(*sline));
 672         ep = result;
 673         sline[0].bol = result;
 674         for (lno = 0, cp = result; cp - result < size; cp++) {
 675                 if (*cp == '\n') {
 676                         sline[lno].lost_tail = &sline[lno].lost_head;
 677                         sline[lno].len = cp - sline[lno].bol;
 678                         sline[lno].flag = 0;
 679                         lno++;
 680                         if (lno < cnt)
 681                                 sline[lno].bol = cp + 1;
 682                 }
 683         }
 684         if (result[size-1] != '\n') {
 685                 sline[cnt-1].lost_tail = &sline[cnt-1].lost_head;
 686                 sline[cnt-1].len = size - (sline[cnt-1].bol - result);
 687                 sline[cnt-1].flag = 0;
 688         }
 689
 690         sline[0].p_lno = xcalloc((cnt+1) * num_parent, sizeof(unsigned long));
 691         for (lno = 0; lno < cnt; lno++)
 692                 sline[lno+1].p_lno = sline[lno].p_lno + num_parent;
 693
 694         for (i = 0; i < num_parent; i++) {
 695                 int j;
 696                 for (j = 0; j < i; j++) {
 697                         if (!memcmp(elem->parent[i].sha1,
 698                                     elem->parent[j].sha1, 20)) {
 699                                 reuse_combine_diff(sline, cnt, i, j);
 700                                 break;
 701                         }
 702                 }
 703                 if (i <= j)
 704                         combine_diff(elem->parent[i].sha1, ourtmp, sline,
 705                                      cnt, i, num_parent);
 706                 if (elem->parent[i].mode != elem->mode)
 707                         mode_differs = 1;
 708         }
 709
 710         show_hunks = make_hunks(sline, cnt, num_parent, dense);
 711
 712         if (show_hunks || mode_differs) {
 713                 const char *abb;
 714                 char null_abb[DEFAULT_ABBREV + 1];
 715
 716                 memset(null_abb, '0', DEFAULT_ABBREV);
 717                 null_abb[DEFAULT_ABBREV] = 0;
 718                 if (header) {
 719                         shown_header++;
 720                         puts(header);
 721                 }
 722                 printf("diff --%s ", dense ? "cc" : "combined");
 723                 if (quote_c_style(elem->path, NULL, NULL, 0))
 724                         quote_c_style(elem->path, NULL, stdout, 0);
 725                 else
 726                         printf("%s", elem->path);
 727                 putchar('\n');
 728                 printf("index ");
 729                 for (i = 0; i < num_parent; i++) {
 730                         if (elem->parent[i].mode != elem->mode)
 731                                 mode_differs = 1;
 732                         if (memcmp(elem->parent[i].sha1, null_sha1, 20))
 733                                 abb = find_unique_abbrev(elem->parent[i].sha1,
 734                                                          DEFAULT_ABBREV);
 735                         else
 736                                 abb = null_abb;
 737                         printf("%s%s", i ? "," : "", abb);
 738                 }
 739                 if (memcmp(elem->sha1, null_sha1, 20))
 740                         abb = find_unique_abbrev(elem->sha1, DEFAULT_ABBREV);
 741                 else
 742                         abb = null_abb;
 743                 printf("..%s\n", abb);
 744
 745                 if (mode_differs) {
 746                         printf("mode ");
 747                         for (i = 0; i < num_parent; i++) {
 748                                 printf("%s%06o", i ? "," : "",
 749                                        elem->parent[i].mode);
 750                         }
 751                         printf("..%06o\n", elem->mode);
 752                 }
 753                 /* if (show_hunks) perhaps */
 754                 dump_sline(sline, cnt, num_parent);
 755         }
 756         if (ourtmp == ourtmp_buf)
 757                 unlink(ourtmp);
 758         free(result);
 759
 760         for (i = 0; i < cnt; i++) {
 761                 if (sline[i].lost_head) {
 762                         struct lline *ll = sline[i].lost_head;
 763                         while (ll) {
 764                                 struct lline *tmp = ll;
 765                                 ll = ll->next;
 766                                 free(tmp);
 767                         }
 768                 }
 769         }
 770         free(sline[0].p_lno);
 771         free(sline);
 772         return shown_header;
 773 }
 774
 775 int diff_tree_combined_merge(const unsigned char *sha1,
 776                              const char *header, int dense)
 777 {
 778         struct commit *commit = lookup_commit(sha1);
 779         struct diff_options diffopts;
 780         struct commit_list *parents;
 781         struct combine_diff_path *p, *paths = NULL;
 782         int num_parent, i, num_paths;
 783
 784         diff_setup(&diffopts);
 785         diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
 786         diffopts.recursive = 1;
 787
 788         /* count parents */
 789         for (parents = commit->parents, num_parent = 0;
 790              parents;
 791              parents = parents->next, num_parent++)
 792                 ; /* nothing */
 793
 794         /* find set of paths that everybody touches */
 795         for (parents = commit->parents, i = 0;
 796              parents;
 797              parents = parents->next, i++) {
 798                 struct commit *parent = parents->item;
 799                 diff_tree_sha1(parent->object.sha1, commit->object.sha1, "",
 800                                &diffopts);
 801                 paths = intersect_paths(paths, i, num_parent);
 802                 diff_flush(&diffopts);
 803         }
 804
 805         /* find out surviving paths */
 806         for (num_paths = 0, p = paths; p; p = p->next) {
 807                 if (p->len)
 808                         num_paths++;
 809         }
 810         if (num_paths) {
 811                 for (p = paths; p; p = p->next) {
 812                         if (!p->len)
 813                                 continue;
 814                         if (show_combined_diff(p, num_parent, dense, header))
 815                                 header = NULL;
 816                 }
 817         }
 818
 819         /* Clean things up */
 820         while (paths) {
 821                 struct combine_diff_path *tmp = paths;
 822                 paths = paths->next;
 823                 free(tmp);
 824         }
 825         return 0;
 826 }