git.oblomov.eu Git - git/blob - combine-diff.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "blob.h"
   4 #include "diff.h"
   5 #include "diffcore.h"
   6 #include "quote.h"
   7 #include "xdiff-interface.h"
   8 #include "log-tree.h"
   9
  10 static struct combine_diff_path *intersect_paths(struct combine_diff_path *curr, int n, int num_parent)
  11 {
  12         struct diff_queue_struct *q = &diff_queued_diff;
  13         struct combine_diff_path *p;
  14         int i;
  15
  16         if (!n) {
  17                 struct combine_diff_path *list = NULL, **tail = &list;
  18                 for (i = 0; i < q->nr; i++) {
  19                         int len;
  20                         const char *path;
  21                         if (diff_unmodified_pair(q->queue[i]))
  22                                 continue;
  23                         path = q->queue[i]->two->path;
  24                         len = strlen(path);
  25                         p = xmalloc(combine_diff_path_size(num_parent, len));
  26                         p->path = (char*) &(p->parent[num_parent]);
  27                         memcpy(p->path, path, len);
  28                         p->path[len] = 0;
  29                         p->len = len;
  30                         p->next = NULL;
  31                         memset(p->parent, 0,
  32                                sizeof(p->parent[0]) * num_parent);
  33
  34                         hashcpy(p->sha1, q->queue[i]->two->sha1);
  35                         p->mode = q->queue[i]->two->mode;
  36                         hashcpy(p->parent[n].sha1, q->queue[i]->one->sha1);
  37                         p->parent[n].mode = q->queue[i]->one->mode;
  38                         p->parent[n].status = q->queue[i]->status;
  39                         *tail = p;
  40                         tail = &p->next;
  41                 }
  42                 return list;
  43         }
  44
  45         for (p = curr; p; p = p->next) {
  46                 int found = 0;
  47                 if (!p->len)
  48                         continue;
  49                 for (i = 0; i < q->nr; i++) {
  50                         const char *path;
  51                         int len;
  52
  53                         if (diff_unmodified_pair(q->queue[i]))
  54                                 continue;
  55                         path = q->queue[i]->two->path;
  56                         len = strlen(path);
  57                         if (len == p->len && !memcmp(path, p->path, len)) {
  58                                 found = 1;
  59                                 hashcpy(p->parent[n].sha1, q->queue[i]->one->sha1);
  60                                 p->parent[n].mode = q->queue[i]->one->mode;
  61                                 p->parent[n].status = q->queue[i]->status;
  62                                 break;
  63                         }
  64                 }
  65                 if (!found)
  66                         p->len = 0;
  67         }
  68         return curr;
  69 }
  70
  71 /* Lines lost from parent */
  72 struct lline {
  73         struct lline *next;
  74         int len;
  75         unsigned long parent_map;
  76         char line[FLEX_ARRAY];
  77 };
  78
  79 /* Lines surviving in the merge result */
  80 struct sline {
  81         struct lline *lost_head, **lost_tail;
  82         char *bol;
  83         int len;
  84         /* bit 0 up to (N-1) are on if the parent has this line (i.e.
  85          * we did not change it).
  86          * bit N is used for "interesting" lines, including context.
  87          */
  88         unsigned long flag;
  89         unsigned long *p_lno;
  90 };
  91
  92 static char *grab_blob(const unsigned char *sha1, unsigned long *size)
  93 {
  94         char *blob;
  95         enum object_type type;
  96         if (is_null_sha1(sha1)) {
  97                 /* deleted blob */
  98                 *size = 0;
  99                 return xcalloc(1, 1);
 100         }
 101         blob = read_sha1_file(sha1, &type, size);
 102         if (type != OBJ_BLOB)
 103                 die("object '%s' is not a blob!", sha1_to_hex(sha1));
 104         return blob;
 105 }
 106
 107 static void append_lost(struct sline *sline, int n, const char *line, int len)
 108 {
 109         struct lline *lline;
 110         unsigned long this_mask = (1UL<<n);
 111         if (line[len-1] == '\n')
 112                 len--;
 113
 114         /* Check to see if we can squash things */
 115         if (sline->lost_head) {
 116                 struct lline *last_one = NULL;
 117                 /* We cannot squash it with earlier one */
 118                 for (lline = sline->lost_head;
 119                      lline;
 120                      lline = lline->next)
 121                         if (lline->parent_map & this_mask)
 122                                 last_one = lline;
 123                 lline = last_one ? last_one->next : sline->lost_head;
 124                 while (lline) {
 125                         if (lline->len == len &&
 126                             !memcmp(lline->line, line, len)) {
 127                                 lline->parent_map |= this_mask;
 128                                 return;
 129                         }
 130                         lline = lline->next;
 131                 }
 132         }
 133
 134         lline = xmalloc(sizeof(*lline) + len + 1);
 135         lline->len = len;
 136         lline->next = NULL;
 137         lline->parent_map = this_mask;
 138         memcpy(lline->line, line, len);
 139         lline->line[len] = 0;
 140         *sline->lost_tail = lline;
 141         sline->lost_tail = &lline->next;
 142 }
 143
 144 struct combine_diff_state {
 145         struct xdiff_emit_state xm;
 146
 147         unsigned int lno;
 148         int ob, on, nb, nn;
 149         unsigned long nmask;
 150         int num_parent;
 151         int n;
 152         struct sline *sline;
 153         struct sline *lost_bucket;
 154 };
 155
 156 static void consume_line(void *state_, char *line, unsigned long len)
 157 {
 158         struct combine_diff_state *state = state_;
 159         if (5 < len && !memcmp("@@ -", line, 4)) {
 160                 if (parse_hunk_header(line, len,
 161                                       &state->ob, &state->on,
 162                                       &state->nb, &state->nn))
 163                         return;
 164                 state->lno = state->nb;
 165                 if (!state->nb)
 166                         /* @@ -1,2 +0,0 @@ to remove the
 167                          * first two lines...
 168                          */
 169                         state->nb = 1;
 170                 if (state->nn == 0)
 171                         /* @@ -X,Y +N,0 @@ removed Y lines
 172                          * that would have come *after* line N
 173                          * in the result.  Our lost buckets hang
 174                          * to the line after the removed lines,
 175                          */
 176                         state->lost_bucket = &state->sline[state->nb];
 177                 else
 178                         state->lost_bucket = &state->sline[state->nb-1];
 179                 if (!state->sline[state->nb-1].p_lno)
 180                         state->sline[state->nb-1].p_lno =
 181                                 xcalloc(state->num_parent,
 182                                         sizeof(unsigned long));
 183                 state->sline[state->nb-1].p_lno[state->n] = state->ob;
 184                 return;
 185         }
 186         if (!state->lost_bucket)
 187                 return; /* not in any hunk yet */
 188         switch (line[0]) {
 189         case '-':
 190                 append_lost(state->lost_bucket, state->n, line+1, len-1);
 191                 break;
 192         case '+':
 193                 state->sline[state->lno-1].flag |= state->nmask;
 194                 state->lno++;
 195                 break;
 196         }
 197 }
 198
 199 static void combine_diff(const unsigned char *parent, mmfile_t *result_file,
 200                          struct sline *sline, unsigned int cnt, int n,
 201                          int num_parent)
 202 {
 203         unsigned int p_lno, lno;
 204         unsigned long nmask = (1UL << n);
 205         xpparam_t xpp;
 206         xdemitconf_t xecfg;
 207         mmfile_t parent_file;
 208         xdemitcb_t ecb;
 209         struct combine_diff_state state;
 210         unsigned long sz;
 211
 212         if (!cnt)
 213                 return; /* result deleted */
 214
 215         parent_file.ptr = grab_blob(parent, &sz);
 216         parent_file.size = sz;
 217         xpp.flags = XDF_NEED_MINIMAL;
 218         memset(&xecfg, 0, sizeof(xecfg));
 219         ecb.outf = xdiff_outf;
 220         ecb.priv = &state;
 221         memset(&state, 0, sizeof(state));
 222         state.xm.consume = consume_line;
 223         state.nmask = nmask;
 224         state.sline = sline;
 225         state.lno = 1;
 226         state.num_parent = num_parent;
 227         state.n = n;
 228
 229         xdl_diff(&parent_file, result_file, &xpp, &xecfg, &ecb);
 230         free(parent_file.ptr);
 231
 232         /* Assign line numbers for this parent.
 233          *
 234          * sline[lno].p_lno[n] records the first line number
 235          * (counting from 1) for parent N if the final hunk display
 236          * started by showing sline[lno] (possibly showing the lost
 237          * lines attached to it first).
 238          */
 239         for (lno = 0,  p_lno = 1; lno <= cnt; lno++) {
 240                 struct lline *ll;
 241                 sline[lno].p_lno[n] = p_lno;
 242
 243                 /* How many lines would this sline advance the p_lno? */
 244                 ll = sline[lno].lost_head;
 245                 while (ll) {
 246                         if (ll->parent_map & nmask)
 247                                 p_lno++; /* '-' means parent had it */
 248                         ll = ll->next;
 249                 }
 250                 if (lno < cnt && !(sline[lno].flag & nmask))
 251                         p_lno++; /* no '+' means parent had it */
 252         }
 253         sline[lno].p_lno[n] = p_lno; /* trailer */
 254 }
 255
 256 static unsigned long context = 3;
 257 static char combine_marker = '@';
 258
 259 static int interesting(struct sline *sline, unsigned long all_mask)
 260 {
 261         /* If some parents lost lines here, or if we have added to
 262          * some parent, it is interesting.
 263          */
 264         return ((sline->flag & all_mask) || sline->lost_head);
 265 }
 266
 267 static unsigned long adjust_hunk_tail(struct sline *sline,
 268                                       unsigned long all_mask,
 269                                       unsigned long hunk_begin,
 270                                       unsigned long i)
 271 {
 272         /* i points at the first uninteresting line.  If the last line
 273          * of the hunk was interesting only because it has some
 274          * deletion, then it is not all that interesting for the
 275          * purpose of giving trailing context lines.  This is because
 276          * we output '-' line and then unmodified sline[i-1] itself in
 277          * that case which gives us one extra context line.
 278          */
 279         if ((hunk_begin + 1 <= i) && !(sline[i-1].flag & all_mask))
 280                 i--;
 281         return i;
 282 }
 283
 284 static unsigned long find_next(struct sline *sline,
 285                                unsigned long mark,
 286                                unsigned long i,
 287                                unsigned long cnt,
 288                                int look_for_uninteresting)
 289 {
 290         /* We have examined up to i-1 and are about to look at i.
 291          * Find next interesting or uninteresting line.  Here,
 292          * "interesting" does not mean interesting(), but marked by
 293          * the give_context() function below (i.e. it includes context
 294          * lines that are not interesting to interesting() function
 295          * that are surrounded by interesting() ones.
 296          */
 297         while (i <= cnt)
 298                 if (look_for_uninteresting
 299                     ? !(sline[i].flag & mark)
 300                     : (sline[i].flag & mark))
 301                         return i;
 302                 else
 303                         i++;
 304         return i;
 305 }
 306
 307 static int give_context(struct sline *sline, unsigned long cnt, int num_parent)
 308 {
 309         unsigned long all_mask = (1UL<<num_parent) - 1;
 310         unsigned long mark = (1UL<<num_parent);
 311         unsigned long i;
 312
 313         /* Two groups of interesting lines may have a short gap of
 314          * uninteresting lines.  Connect such groups to give them a
 315          * bit of context.
 316          *
 317          * We first start from what the interesting() function says,
 318          * and mark them with "mark", and paint context lines with the
 319          * mark.  So interesting() would still say false for such context
 320          * lines but they are treated as "interesting" in the end.
 321          */
 322         i = find_next(sline, mark, 0, cnt, 0);
 323         if (cnt < i)
 324                 return 0;
 325
 326         while (i <= cnt) {
 327                 unsigned long j = (context < i) ? (i - context) : 0;
 328                 unsigned long k;
 329
 330                 /* Paint a few lines before the first interesting line. */
 331                 while (j < i)
 332                         sline[j++].flag |= mark;
 333
 334         again:
 335                 /* we know up to i is to be included.  where does the
 336                  * next uninteresting one start?
 337                  */
 338                 j = find_next(sline, mark, i, cnt, 1);
 339                 if (cnt < j)
 340                         break; /* the rest are all interesting */
 341
 342                 /* lookahead context lines */
 343                 k = find_next(sline, mark, j, cnt, 0);
 344                 j = adjust_hunk_tail(sline, all_mask, i, j);
 345
 346                 if (k < j + context) {
 347                         /* k is interesting and [j,k) are not, but
 348                          * paint them interesting because the gap is small.
 349                          */
 350                         while (j < k)
 351                                 sline[j++].flag |= mark;
 352                         i = k;
 353                         goto again;
 354                 }
 355
 356                 /* j is the first uninteresting line and there is
 357                  * no overlap beyond it within context lines.  Paint
 358                  * the trailing edge a bit.
 359                  */
 360                 i = k;
 361                 k = (j + context < cnt+1) ? j + context : cnt+1;
 362                 while (j < k)
 363                         sline[j++].flag |= mark;
 364         }
 365         return 1;
 366 }
 367
 368 static int make_hunks(struct sline *sline, unsigned long cnt,
 369                        int num_parent, int dense)
 370 {
 371         unsigned long all_mask = (1UL<<num_parent) - 1;
 372         unsigned long mark = (1UL<<num_parent);
 373         unsigned long i;
 374         int has_interesting = 0;
 375
 376         for (i = 0; i <= cnt; i++) {
 377                 if (interesting(&sline[i], all_mask))
 378                         sline[i].flag |= mark;
 379                 else
 380                         sline[i].flag &= ~mark;
 381         }
 382         if (!dense)
 383                 return give_context(sline, cnt, num_parent);
 384
 385         /* Look at each hunk, and if we have changes from only one
 386          * parent, or the changes are the same from all but one
 387          * parent, mark that uninteresting.
 388          */
 389         i = 0;
 390         while (i <= cnt) {
 391                 unsigned long j, hunk_begin, hunk_end;
 392                 unsigned long same_diff;
 393                 while (i <= cnt && !(sline[i].flag & mark))
 394                         i++;
 395                 if (cnt < i)
 396                         break; /* No more interesting hunks */
 397                 hunk_begin = i;
 398                 for (j = i + 1; j <= cnt; j++) {
 399                         if (!(sline[j].flag & mark)) {
 400                                 /* Look beyond the end to see if there
 401                                  * is an interesting line after this
 402                                  * hunk within context span.
 403                                  */
 404                                 unsigned long la; /* lookahead */
 405                                 int contin = 0;
 406                                 la = adjust_hunk_tail(sline, all_mask,
 407                                                      hunk_begin, j);
 408                                 la = (la + context < cnt + 1) ?
 409                                         (la + context) : cnt + 1;
 410                                 while (j <= --la) {
 411                                         if (sline[la].flag & mark) {
 412                                                 contin = 1;
 413                                                 break;
 414                                         }
 415                                 }
 416                                 if (!contin)
 417                                         break;
 418                                 j = la;
 419                         }
 420                 }
 421                 hunk_end = j;
 422
 423                 /* [i..hunk_end) are interesting.  Now is it really
 424                  * interesting?  We check if there are only two versions
 425                  * and the result matches one of them.  That is, we look
 426                  * at:
 427                  *   (+) line, which records lines added to which parents;
 428                  *       this line appears in the result.
 429                  *   (-) line, which records from what parents the line
 430                  *       was removed; this line does not appear in the result.
 431                  * then check the set of parents the result has difference
 432                  * from, from all lines.  If there are lines that has
 433                  * different set of parents that the result has differences
 434                  * from, that means we have more than two versions.
 435                  *
 436                  * Even when we have only two versions, if the result does
 437                  * not match any of the parents, the it should be considered
 438                  * interesting.  In such a case, we would have all '+' line.
 439                  * After passing the above "two versions" test, that would
 440                  * appear as "the same set of parents" to be "all parents".
 441                  */
 442                 same_diff = 0;
 443                 has_interesting = 0;
 444                 for (j = i; j < hunk_end && !has_interesting; j++) {
 445                         unsigned long this_diff = sline[j].flag & all_mask;
 446                         struct lline *ll = sline[j].lost_head;
 447                         if (this_diff) {
 448                                 /* This has some changes.  Is it the
 449                                  * same as others?
 450                                  */
 451                                 if (!same_diff)
 452                                         same_diff = this_diff;
 453                                 else if (same_diff != this_diff) {
 454                                         has_interesting = 1;
 455                                         break;
 456                                 }
 457                         }
 458                         while (ll && !has_interesting) {
 459                                 /* Lost this line from these parents;
 460                                  * who are they?  Are they the same?
 461                                  */
 462                                 this_diff = ll->parent_map;
 463                                 if (!same_diff)
 464                                         same_diff = this_diff;
 465                                 else if (same_diff != this_diff) {
 466                                         has_interesting = 1;
 467                                 }
 468                                 ll = ll->next;
 469                         }
 470                 }
 471
 472                 if (!has_interesting && same_diff != all_mask) {
 473                         /* This hunk is not that interesting after all */
 474                         for (j = hunk_begin; j < hunk_end; j++)
 475                                 sline[j].flag &= ~mark;
 476                 }
 477                 i = hunk_end;
 478         }
 479
 480         has_interesting = give_context(sline, cnt, num_parent);
 481         return has_interesting;
 482 }
 483
 484 static void show_parent_lno(struct sline *sline, unsigned long l0, unsigned long l1, int n, unsigned long null_context)
 485 {
 486         l0 = sline[l0].p_lno[n];
 487         l1 = sline[l1].p_lno[n];
 488         printf(" -%lu,%lu", l0, l1-l0-null_context);
 489 }
 490
 491 static int hunk_comment_line(const char *bol)
 492 {
 493         int ch;
 494
 495         if (!bol)
 496                 return 0;
 497         ch = *bol & 0xff;
 498         return (isalpha(ch) || ch == '_' || ch == '$');
 499 }
 500
 501 static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
 502                        int use_color)
 503 {
 504         unsigned long mark = (1UL<<num_parent);
 505         int i;
 506         unsigned long lno = 0;
 507         const char *c_frag = diff_get_color(use_color, DIFF_FRAGINFO);
 508         const char *c_new = diff_get_color(use_color, DIFF_FILE_NEW);
 509         const char *c_old = diff_get_color(use_color, DIFF_FILE_OLD);
 510         const char *c_plain = diff_get_color(use_color, DIFF_PLAIN);
 511         const char *c_reset = diff_get_color(use_color, DIFF_RESET);
 512
 513         if (!cnt)
 514                 return; /* result deleted */
 515
 516         while (1) {
 517                 struct sline *sl = &sline[lno];
 518                 unsigned long hunk_end;
 519                 unsigned long rlines;
 520                 const char *hunk_comment = NULL;
 521                 unsigned long null_context = 0;
 522
 523                 while (lno <= cnt && !(sline[lno].flag & mark)) {
 524                         if (hunk_comment_line(sline[lno].bol))
 525                                 hunk_comment = sline[lno].bol;
 526                         lno++;
 527                 }
 528                 if (cnt < lno)
 529                         break;
 530                 else {
 531                         for (hunk_end = lno + 1; hunk_end <= cnt; hunk_end++)
 532                                 if (!(sline[hunk_end].flag & mark))
 533                                         break;
 534                 }
 535                 rlines = hunk_end - lno;
 536                 if (cnt < hunk_end)
 537                         rlines--; /* pointing at the last delete hunk */
 538
 539                 if (!context) {
 540                         /*
 541                          * Even when running with --unified=0, all
 542                          * lines in the hunk needs to be processed in
 543                          * the loop below in order to show the
 544                          * deletion recorded in lost_head.  However,
 545                          * we do not want to show the resulting line
 546                          * with all blank context markers in such a
 547                          * case.  Compensate.
 548                          */
 549                         unsigned long j;
 550                         for (j = lno; j < hunk_end; j++)
 551                                 if (!(sline[j].flag & (mark-1)))
 552                                         null_context++;
 553                         rlines -= null_context;
 554                 }
 555
 556                 fputs(c_frag, stdout);
 557                 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
 558                 for (i = 0; i < num_parent; i++)
 559                         show_parent_lno(sline, lno, hunk_end, i, null_context);
 560                 printf(" +%lu,%lu ", lno+1, rlines);
 561                 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
 562
 563                 if (hunk_comment) {
 564                         int comment_end = 0;
 565                         for (i = 0; i < 40; i++) {
 566                                 int ch = hunk_comment[i] & 0xff;
 567                                 if (!ch || ch == '\n')
 568                                         break;
 569                                 if (!isspace(ch))
 570                                     comment_end = i;
 571                         }
 572                         if (comment_end)
 573                                 putchar(' ');
 574                         for (i = 0; i < comment_end; i++)
 575                                 putchar(hunk_comment[i]);
 576                 }
 577
 578                 printf("%s\n", c_reset);
 579                 while (lno < hunk_end) {
 580                         struct lline *ll;
 581                         int j;
 582                         unsigned long p_mask;
 583                         sl = &sline[lno++];
 584                         ll = sl->lost_head;
 585                         while (ll) {
 586                                 fputs(c_old, stdout);
 587                                 for (j = 0; j < num_parent; j++) {
 588                                         if (ll->parent_map & (1UL<<j))
 589                                                 putchar('-');
 590                                         else
 591                                                 putchar(' ');
 592                                 }
 593                                 printf("%s%s\n", ll->line, c_reset);
 594                                 ll = ll->next;
 595                         }
 596                         if (cnt < lno)
 597                                 break;
 598                         p_mask = 1;
 599                         if (!(sl->flag & (mark-1))) {
 600                                 /*
 601                                  * This sline was here to hang the
 602                                  * lost lines in front of it.
 603                                  */
 604                                 if (!context)
 605                                         continue;
 606                                 fputs(c_plain, stdout);
 607                         }
 608                         else
 609                                 fputs(c_new, stdout);
 610                         for (j = 0; j < num_parent; j++) {
 611                                 if (p_mask & sl->flag)
 612                                         putchar('+');
 613                                 else
 614                                         putchar(' ');
 615                                 p_mask <<= 1;
 616                         }
 617                         printf("%.*s%s\n", sl->len, sl->bol, c_reset);
 618                 }
 619         }
 620 }
 621
 622 static void reuse_combine_diff(struct sline *sline, unsigned long cnt,
 623                                int i, int j)
 624 {
 625         /* We have already examined parent j and we know parent i
 626          * and parent j are the same, so reuse the combined result
 627          * of parent j for parent i.
 628          */
 629         unsigned long lno, imask, jmask;
 630         imask = (1UL<<i);
 631         jmask = (1UL<<j);
 632
 633         for (lno = 0; lno <= cnt; lno++) {
 634                 struct lline *ll = sline->lost_head;
 635                 sline->p_lno[i] = sline->p_lno[j];
 636                 while (ll) {
 637                         if (ll->parent_map & jmask)
 638                                 ll->parent_map |= imask;
 639                         ll = ll->next;
 640                 }
 641                 if (sline->flag & jmask)
 642                         sline->flag |= imask;
 643                 sline++;
 644         }
 645         /* the overall size of the file (sline[cnt]) */
 646         sline->p_lno[i] = sline->p_lno[j];
 647 }
 648
 649 static void dump_quoted_path(const char *prefix, const char *path,
 650                              const char *c_meta, const char *c_reset)
 651 {
 652         printf("%s%s", c_meta, prefix);
 653         quote_c_style(path, NULL, stdout, 0);
 654         printf("%s\n", c_reset);
 655 }
 656
 657 static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
 658                             int dense, struct rev_info *rev)
 659 {
 660         struct diff_options *opt = &rev->diffopt;
 661         unsigned long result_size, cnt, lno;
 662         char *result, *cp;
 663         struct sline *sline; /* survived lines */
 664         int mode_differs = 0;
 665         int i, show_hunks;
 666         int working_tree_file = is_null_sha1(elem->sha1);
 667         int abbrev = opt->full_index ? 40 : DEFAULT_ABBREV;
 668         mmfile_t result_file;
 669
 670         context = opt->context;
 671         /* Read the result of merge first */
 672         if (!working_tree_file)
 673                 result = grab_blob(elem->sha1, &result_size);
 674         else {
 675                 /* Used by diff-tree to read from the working tree */
 676                 struct stat st;
 677                 int fd = -1;
 678
 679                 if (lstat(elem->path, &st) < 0)
 680                         goto deleted_file;
 681
 682                 if (S_ISLNK(st.st_mode)) {
 683                         size_t len = xsize_t(st.st_size);
 684                         result_size = len;
 685                         result = xmalloc(len + 1);
 686                         if (result_size != readlink(elem->path, result, len)) {
 687                                 error("readlink(%s): %s", elem->path,
 688                                       strerror(errno));
 689                                 return;
 690                         }
 691                         result[len] = 0;
 692                         elem->mode = canon_mode(st.st_mode);
 693                 }
 694                 else if (0 <= (fd = open(elem->path, O_RDONLY)) &&
 695                          !fstat(fd, &st)) {
 696                         size_t len = xsize_t(st.st_size);
 697                         size_t sz = 0;
 698                         int is_file, i;
 699
 700                         elem->mode = canon_mode(st.st_mode);
 701                         /* if symlinks don't work, assume symlink if all parents
 702                          * are symlinks
 703                          */
 704                         is_file = has_symlinks;
 705                         for (i = 0; !is_file && i < num_parent; i++)
 706                                 is_file = !S_ISLNK(elem->parent[i].mode);
 707                         if (!is_file)
 708                                 elem->mode = canon_mode(S_IFLNK);
 709
 710                         result_size = len;
 711                         result = xmalloc(len + 1);
 712                         while (sz < len) {
 713                                 ssize_t done = xread(fd, result+sz, len-sz);
 714                                 if (done == 0)
 715                                         break;
 716                                 if (done < 0)
 717                                         die("read error '%s'", elem->path);
 718                                 sz += done;
 719                         }
 720                         result[len] = 0;
 721                 }
 722                 else {
 723                 deleted_file:
 724                         result_size = 0;
 725                         elem->mode = 0;
 726                         result = xcalloc(1, 1);
 727                 }
 728
 729                 if (0 <= fd)
 730                         close(fd);
 731         }
 732
 733         for (cnt = 0, cp = result; cp < result + result_size; cp++) {
 734                 if (*cp == '\n')
 735                         cnt++;
 736         }
 737         if (result_size && result[result_size-1] != '\n')
 738                 cnt++; /* incomplete line */
 739
 740         sline = xcalloc(cnt+2, sizeof(*sline));
 741         sline[0].bol = result;
 742         for (lno = 0; lno <= cnt + 1; lno++) {
 743                 sline[lno].lost_tail = &sline[lno].lost_head;
 744                 sline[lno].flag = 0;
 745         }
 746         for (lno = 0, cp = result; cp < result + result_size; cp++) {
 747                 if (*cp == '\n') {
 748                         sline[lno].len = cp - sline[lno].bol;
 749                         lno++;
 750                         if (lno < cnt)
 751                                 sline[lno].bol = cp + 1;
 752                 }
 753         }
 754         if (result_size && result[result_size-1] != '\n')
 755                 sline[cnt-1].len = result_size - (sline[cnt-1].bol - result);
 756
 757         result_file.ptr = result;
 758         result_file.size = result_size;
 759
 760         /* Even p_lno[cnt+1] is valid -- that is for the end line number
 761          * for deletion hunk at the end.
 762          */
 763         sline[0].p_lno = xcalloc((cnt+2) * num_parent, sizeof(unsigned long));
 764         for (lno = 0; lno <= cnt; lno++)
 765                 sline[lno+1].p_lno = sline[lno].p_lno + num_parent;
 766
 767         for (i = 0; i < num_parent; i++) {
 768                 int j;
 769                 for (j = 0; j < i; j++) {
 770                         if (!hashcmp(elem->parent[i].sha1,
 771                                      elem->parent[j].sha1)) {
 772                                 reuse_combine_diff(sline, cnt, i, j);
 773                                 break;
 774                         }
 775                 }
 776                 if (i <= j)
 777                         combine_diff(elem->parent[i].sha1, &result_file, sline,
 778                                      cnt, i, num_parent);
 779                 if (elem->parent[i].mode != elem->mode)
 780                         mode_differs = 1;
 781         }
 782
 783         show_hunks = make_hunks(sline, cnt, num_parent, dense);
 784
 785         if (show_hunks || mode_differs || working_tree_file) {
 786                 const char *abb;
 787                 int use_color = opt->color_diff;
 788                 const char *c_meta = diff_get_color(use_color, DIFF_METAINFO);
 789                 const char *c_reset = diff_get_color(use_color, DIFF_RESET);
 790                 int added = 0;
 791                 int deleted = 0;
 792
 793                 if (rev->loginfo && !rev->no_commit_id)
 794                         show_log(rev, opt->msg_sep);
 795                 dump_quoted_path(dense ? "diff --cc " : "diff --combined ",
 796                                  elem->path, c_meta, c_reset);
 797                 printf("%sindex ", c_meta);
 798                 for (i = 0; i < num_parent; i++) {
 799                         abb = find_unique_abbrev(elem->parent[i].sha1,
 800                                                  abbrev);
 801                         printf("%s%s", i ? "," : "", abb);
 802                 }
 803                 abb = find_unique_abbrev(elem->sha1, abbrev);
 804                 printf("..%s%s\n", abb, c_reset);
 805
 806                 if (mode_differs) {
 807                         deleted = !elem->mode;
 808
 809                         /* We say it was added if nobody had it */
 810                         added = !deleted;
 811                         for (i = 0; added && i < num_parent; i++)
 812                                 if (elem->parent[i].status !=
 813                                     DIFF_STATUS_ADDED)
 814                                         added = 0;
 815                         if (added)
 816                                 printf("%snew file mode %06o",
 817                                        c_meta, elem->mode);
 818                         else {
 819                                 if (deleted)
 820                                         printf("%sdeleted file ", c_meta);
 821                                 printf("mode ");
 822                                 for (i = 0; i < num_parent; i++) {
 823                                         printf("%s%06o", i ? "," : "",
 824                                                elem->parent[i].mode);
 825                                 }
 826                                 if (elem->mode)
 827                                         printf("..%06o", elem->mode);
 828                         }
 829                         printf("%s\n", c_reset);
 830                 }
 831                 if (added)
 832                         dump_quoted_path("--- /dev/", "null", c_meta, c_reset);
 833                 else
 834                         dump_quoted_path("--- a/", elem->path, c_meta, c_reset);
 835                 if (deleted)
 836                         dump_quoted_path("+++ /dev/", "null", c_meta, c_reset);
 837                 else
 838                         dump_quoted_path("+++ b/", elem->path, c_meta, c_reset);
 839                 dump_sline(sline, cnt, num_parent, opt->color_diff);
 840         }
 841         free(result);
 842
 843         for (lno = 0; lno < cnt; lno++) {
 844                 if (sline[lno].lost_head) {
 845                         struct lline *ll = sline[lno].lost_head;
 846                         while (ll) {
 847                                 struct lline *tmp = ll;
 848                                 ll = ll->next;
 849                                 free(tmp);
 850                         }
 851                 }
 852         }
 853         free(sline[0].p_lno);
 854         free(sline);
 855 }
 856
 857 #define COLONS "::::::::::::::::::::::::::::::::"
 858
 859 static void show_raw_diff(struct combine_diff_path *p, int num_parent, struct rev_info *rev)
 860 {
 861         struct diff_options *opt = &rev->diffopt;
 862         int i, offset;
 863         const char *prefix;
 864         int line_termination, inter_name_termination;
 865
 866         line_termination = opt->line_termination;
 867         inter_name_termination = '\t';
 868         if (!line_termination)
 869                 inter_name_termination = 0;
 870
 871         if (rev->loginfo && !rev->no_commit_id)
 872                 show_log(rev, opt->msg_sep);
 873
 874         if (opt->output_format & DIFF_FORMAT_RAW) {
 875                 offset = strlen(COLONS) - num_parent;
 876                 if (offset < 0)
 877                         offset = 0;
 878                 prefix = COLONS + offset;
 879
 880                 /* Show the modes */
 881                 for (i = 0; i < num_parent; i++) {
 882                         printf("%s%06o", prefix, p->parent[i].mode);
 883                         prefix = " ";
 884                 }
 885                 printf("%s%06o", prefix, p->mode);
 886
 887                 /* Show sha1's */
 888                 for (i = 0; i < num_parent; i++)
 889                         printf(" %s", diff_unique_abbrev(p->parent[i].sha1,
 890                                                          opt->abbrev));
 891                 printf(" %s ", diff_unique_abbrev(p->sha1, opt->abbrev));
 892         }
 893
 894         if (opt->output_format & (DIFF_FORMAT_RAW | DIFF_FORMAT_NAME_STATUS)) {
 895                 for (i = 0; i < num_parent; i++)
 896                         putchar(p->parent[i].status);
 897                 putchar(inter_name_termination);
 898         }
 899
 900         write_name_quoted(p->path, stdout, line_termination);
 901 }
 902
 903 void show_combined_diff(struct combine_diff_path *p,
 904                        int num_parent,
 905                        int dense,
 906                        struct rev_info *rev)
 907 {
 908         struct diff_options *opt = &rev->diffopt;
 909         if (!p->len)
 910                 return;
 911         if (opt->output_format & (DIFF_FORMAT_RAW |
 912                                   DIFF_FORMAT_NAME |
 913                                   DIFF_FORMAT_NAME_STATUS))
 914                 show_raw_diff(p, num_parent, rev);
 915         else if (opt->output_format & DIFF_FORMAT_PATCH)
 916                 show_patch_diff(p, num_parent, dense, rev);
 917 }
 918
 919 void diff_tree_combined(const unsigned char *sha1,
 920                         const unsigned char parent[][20],
 921                         int num_parent,
 922                         int dense,
 923                         struct rev_info *rev)
 924 {
 925         struct diff_options *opt = &rev->diffopt;
 926         struct diff_options diffopts;
 927         struct combine_diff_path *p, *paths = NULL;
 928         int i, num_paths, needsep, show_log_first;
 929
 930         diffopts = *opt;
 931         diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
 932         diffopts.recursive = 1;
 933         diffopts.allow_external = 0;
 934
 935         show_log_first = !!rev->loginfo && !rev->no_commit_id;
 936         needsep = 0;
 937         /* find set of paths that everybody touches */
 938         for (i = 0; i < num_parent; i++) {
 939                 /* show stat against the first parent even
 940                  * when doing combined diff.
 941                  */
 942                 int stat_opt = (opt->output_format &
 943                                 (DIFF_FORMAT_NUMSTAT|DIFF_FORMAT_DIFFSTAT));
 944                 if (i == 0 && stat_opt)
 945                         diffopts.output_format = stat_opt;
 946                 else
 947                         diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
 948                 diff_tree_sha1(parent[i], sha1, "", &diffopts);
 949                 diffcore_std(&diffopts);
 950                 paths = intersect_paths(paths, i, num_parent);
 951
 952                 if (show_log_first && i == 0) {
 953                         show_log(rev, opt->msg_sep);
 954                         if (rev->verbose_header && opt->output_format)
 955                                 putchar(opt->line_termination);
 956                 }
 957                 diff_flush(&diffopts);
 958         }
 959
 960         /* find out surviving paths */
 961         for (num_paths = 0, p = paths; p; p = p->next) {
 962                 if (p->len)
 963                         num_paths++;
 964         }
 965         if (num_paths) {
 966                 if (opt->output_format & (DIFF_FORMAT_RAW |
 967                                           DIFF_FORMAT_NAME |
 968                                           DIFF_FORMAT_NAME_STATUS)) {
 969                         for (p = paths; p; p = p->next) {
 970                                 if (p->len)
 971                                         show_raw_diff(p, num_parent, rev);
 972                         }
 973                         needsep = 1;
 974                 }
 975                 else if (opt->output_format &
 976                          (DIFF_FORMAT_NUMSTAT|DIFF_FORMAT_DIFFSTAT))
 977                         needsep = 1;
 978                 if (opt->output_format & DIFF_FORMAT_PATCH) {
 979                         if (needsep)
 980                                 putchar(opt->line_termination);
 981                         for (p = paths; p; p = p->next) {
 982                                 if (p->len)
 983                                         show_patch_diff(p, num_parent, dense,
 984                                                         rev);
 985                         }
 986                 }
 987         }
 988
 989         /* Clean things up */
 990         while (paths) {
 991                 struct combine_diff_path *tmp = paths;
 992                 paths = paths->next;
 993                 free(tmp);
 994         }
 995 }
 996
 997 void diff_tree_combined_merge(const unsigned char *sha1,
 998                              int dense, struct rev_info *rev)
 999 {
1000         int num_parent;
1001         const unsigned char (*parent)[20];
1002         struct commit *commit = lookup_commit(sha1);
1003         struct commit_list *parents;
1004
1005         /* count parents */
1006         for (parents = commit->parents, num_parent = 0;
1007              parents;
1008              parents = parents->next, num_parent++)
1009                 ; /* nothing */
1010
1011         parent = xmalloc(num_parent * sizeof(*parent));
1012         for (parents = commit->parents, num_parent = 0;
1013              parents;
1014              parents = parents->next, num_parent++)
1015                 hashcpy((unsigned char*)(parent + num_parent),
1016                         parents->item->object.sha1);
1017         diff_tree_combined(sha1, parent, num_parent, dense, rev);
1018 }