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         xecfg.ctxlen = 0;
 219         xecfg.flags = 0;
 220         ecb.outf = xdiff_outf;
 221         ecb.priv = &state;
 222         memset(&state, 0, sizeof(state));
 223         state.xm.consume = consume_line;
 224         state.nmask = nmask;
 225         state.sline = sline;
 226         state.lno = 1;
 227         state.num_parent = num_parent;
 228         state.n = n;
 229
 230         xdl_diff(&parent_file, result_file, &xpp, &xecfg, &ecb);
 231         free(parent_file.ptr);
 232
 233         /* Assign line numbers for this parent.
 234          *
 235          * sline[lno].p_lno[n] records the first line number
 236          * (counting from 1) for parent N if the final hunk display
 237          * started by showing sline[lno] (possibly showing the lost
 238          * lines attached to it first).
 239          */
 240         for (lno = 0,  p_lno = 1; lno <= cnt; lno++) {
 241                 struct lline *ll;
 242                 sline[lno].p_lno[n] = p_lno;
 243
 244                 /* How many lines would this sline advance the p_lno? */
 245                 ll = sline[lno].lost_head;
 246                 while (ll) {
 247                         if (ll->parent_map & nmask)
 248                                 p_lno++; /* '-' means parent had it */
 249                         ll = ll->next;
 250                 }
 251                 if (lno < cnt && !(sline[lno].flag & nmask))
 252                         p_lno++; /* no '+' means parent had it */
 253         }
 254         sline[lno].p_lno[n] = p_lno; /* trailer */
 255 }
 256
 257 static unsigned long context = 3;
 258 static char combine_marker = '@';
 259
 260 static int interesting(struct sline *sline, unsigned long all_mask)
 261 {
 262         /* If some parents lost lines here, or if we have added to
 263          * some parent, it is interesting.
 264          */
 265         return ((sline->flag & all_mask) || sline->lost_head);
 266 }
 267
 268 static unsigned long adjust_hunk_tail(struct sline *sline,
 269                                       unsigned long all_mask,
 270                                       unsigned long hunk_begin,
 271                                       unsigned long i)
 272 {
 273         /* i points at the first uninteresting line.  If the last line
 274          * of the hunk was interesting only because it has some
 275          * deletion, then it is not all that interesting for the
 276          * purpose of giving trailing context lines.  This is because
 277          * we output '-' line and then unmodified sline[i-1] itself in
 278          * that case which gives us one extra context line.
 279          */
 280         if ((hunk_begin + 1 <= i) && !(sline[i-1].flag & all_mask))
 281                 i--;
 282         return i;
 283 }
 284
 285 static unsigned long find_next(struct sline *sline,
 286                                unsigned long mark,
 287                                unsigned long i,
 288                                unsigned long cnt,
 289                                int look_for_uninteresting)
 290 {
 291         /* We have examined up to i-1 and are about to look at i.
 292          * Find next interesting or uninteresting line.  Here,
 293          * "interesting" does not mean interesting(), but marked by
 294          * the give_context() function below (i.e. it includes context
 295          * lines that are not interesting to interesting() function
 296          * that are surrounded by interesting() ones.
 297          */
 298         while (i <= cnt)
 299                 if (look_for_uninteresting
 300                     ? !(sline[i].flag & mark)
 301                     : (sline[i].flag & mark))
 302                         return i;
 303                 else
 304                         i++;
 305         return i;
 306 }
 307
 308 static int give_context(struct sline *sline, unsigned long cnt, int num_parent)
 309 {
 310         unsigned long all_mask = (1UL<<num_parent) - 1;
 311         unsigned long mark = (1UL<<num_parent);
 312         unsigned long i;
 313
 314         /* Two groups of interesting lines may have a short gap of
 315          * uninteresting lines.  Connect such groups to give them a
 316          * bit of context.
 317          *
 318          * We first start from what the interesting() function says,
 319          * and mark them with "mark", and paint context lines with the
 320          * mark.  So interesting() would still say false for such context
 321          * lines but they are treated as "interesting" in the end.
 322          */
 323         i = find_next(sline, mark, 0, cnt, 0);
 324         if (cnt < i)
 325                 return 0;
 326
 327         while (i <= cnt) {
 328                 unsigned long j = (context < i) ? (i - context) : 0;
 329                 unsigned long k;
 330
 331                 /* Paint a few lines before the first interesting line. */
 332                 while (j < i)
 333                         sline[j++].flag |= mark;
 334
 335         again:
 336                 /* we know up to i is to be included.  where does the
 337                  * next uninteresting one start?
 338                  */
 339                 j = find_next(sline, mark, i, cnt, 1);
 340                 if (cnt < j)
 341                         break; /* the rest are all interesting */
 342
 343                 /* lookahead context lines */
 344                 k = find_next(sline, mark, j, cnt, 0);
 345                 j = adjust_hunk_tail(sline, all_mask, i, j);
 346
 347                 if (k < j + context) {
 348                         /* k is interesting and [j,k) are not, but
 349                          * paint them interesting because the gap is small.
 350                          */
 351                         while (j < k)
 352                                 sline[j++].flag |= mark;
 353                         i = k;
 354                         goto again;
 355                 }
 356
 357                 /* j is the first uninteresting line and there is
 358                  * no overlap beyond it within context lines.  Paint
 359                  * the trailing edge a bit.
 360                  */
 361                 i = k;
 362                 k = (j + context < cnt+1) ? j + context : cnt+1;
 363                 while (j < k)
 364                         sline[j++].flag |= mark;
 365         }
 366         return 1;
 367 }
 368
 369 static int make_hunks(struct sline *sline, unsigned long cnt,
 370                        int num_parent, int dense)
 371 {
 372         unsigned long all_mask = (1UL<<num_parent) - 1;
 373         unsigned long mark = (1UL<<num_parent);
 374         unsigned long i;
 375         int has_interesting = 0;
 376
 377         for (i = 0; i <= cnt; i++) {
 378                 if (interesting(&sline[i], all_mask))
 379                         sline[i].flag |= mark;
 380                 else
 381                         sline[i].flag &= ~mark;
 382         }
 383         if (!dense)
 384                 return give_context(sline, cnt, num_parent);
 385
 386         /* Look at each hunk, and if we have changes from only one
 387          * parent, or the changes are the same from all but one
 388          * parent, mark that uninteresting.
 389          */
 390         i = 0;
 391         while (i <= cnt) {
 392                 unsigned long j, hunk_begin, hunk_end;
 393                 unsigned long same_diff;
 394                 while (i <= cnt && !(sline[i].flag & mark))
 395                         i++;
 396                 if (cnt < i)
 397                         break; /* No more interesting hunks */
 398                 hunk_begin = i;
 399                 for (j = i + 1; j <= cnt; j++) {
 400                         if (!(sline[j].flag & mark)) {
 401                                 /* Look beyond the end to see if there
 402                                  * is an interesting line after this
 403                                  * hunk within context span.
 404                                  */
 405                                 unsigned long la; /* lookahead */
 406                                 int contin = 0;
 407                                 la = adjust_hunk_tail(sline, all_mask,
 408                                                      hunk_begin, j);
 409                                 la = (la + context < cnt + 1) ?
 410                                         (la + context) : cnt + 1;
 411                                 while (j <= --la) {
 412                                         if (sline[la].flag & mark) {
 413                                                 contin = 1;
 414                                                 break;
 415                                         }
 416                                 }
 417                                 if (!contin)
 418                                         break;
 419                                 j = la;
 420                         }
 421                 }
 422                 hunk_end = j;
 423
 424                 /* [i..hunk_end) are interesting.  Now is it really
 425                  * interesting?  We check if there are only two versions
 426                  * and the result matches one of them.  That is, we look
 427                  * at:
 428                  *   (+) line, which records lines added to which parents;
 429                  *       this line appears in the result.
 430                  *   (-) line, which records from what parents the line
 431                  *       was removed; this line does not appear in the result.
 432                  * then check the set of parents the result has difference
 433                  * from, from all lines.  If there are lines that has
 434                  * different set of parents that the result has differences
 435                  * from, that means we have more than two versions.
 436                  *
 437                  * Even when we have only two versions, if the result does
 438                  * not match any of the parents, the it should be considered
 439                  * interesting.  In such a case, we would have all '+' line.
 440                  * After passing the above "two versions" test, that would
 441                  * appear as "the same set of parents" to be "all parents".
 442                  */
 443                 same_diff = 0;
 444                 has_interesting = 0;
 445                 for (j = i; j < hunk_end && !has_interesting; j++) {
 446                         unsigned long this_diff = sline[j].flag & all_mask;
 447                         struct lline *ll = sline[j].lost_head;
 448                         if (this_diff) {
 449                                 /* This has some changes.  Is it the
 450                                  * same as others?
 451                                  */
 452                                 if (!same_diff)
 453                                         same_diff = this_diff;
 454                                 else if (same_diff != this_diff) {
 455                                         has_interesting = 1;
 456                                         break;
 457                                 }
 458                         }
 459                         while (ll && !has_interesting) {
 460                                 /* Lost this line from these parents;
 461                                  * who are they?  Are they the same?
 462                                  */
 463                                 this_diff = ll->parent_map;
 464                                 if (!same_diff)
 465                                         same_diff = this_diff;
 466                                 else if (same_diff != this_diff) {
 467                                         has_interesting = 1;
 468                                 }
 469                                 ll = ll->next;
 470                         }
 471                 }
 472
 473                 if (!has_interesting && same_diff != all_mask) {
 474                         /* This hunk is not that interesting after all */
 475                         for (j = hunk_begin; j < hunk_end; j++)
 476                                 sline[j].flag &= ~mark;
 477                 }
 478                 i = hunk_end;
 479         }
 480
 481         has_interesting = give_context(sline, cnt, num_parent);
 482         return has_interesting;
 483 }
 484
 485 static void show_parent_lno(struct sline *sline, unsigned long l0, unsigned long l1, int n, unsigned long null_context)
 486 {
 487         l0 = sline[l0].p_lno[n];
 488         l1 = sline[l1].p_lno[n];
 489         printf(" -%lu,%lu", l0, l1-l0-null_context);
 490 }
 491
 492 static int hunk_comment_line(const char *bol)
 493 {
 494         int ch;
 495
 496         if (!bol)
 497                 return 0;
 498         ch = *bol & 0xff;
 499         return (isalpha(ch) || ch == '_' || ch == '$');
 500 }
 501
 502 static void dump_sline(struct sline *sline, unsigned long cnt, int num_parent,
 503                        int use_color)
 504 {
 505         unsigned long mark = (1UL<<num_parent);
 506         int i;
 507         unsigned long lno = 0;
 508         const char *c_frag = diff_get_color(use_color, DIFF_FRAGINFO);
 509         const char *c_new = diff_get_color(use_color, DIFF_FILE_NEW);
 510         const char *c_old = diff_get_color(use_color, DIFF_FILE_OLD);
 511         const char *c_plain = diff_get_color(use_color, DIFF_PLAIN);
 512         const char *c_reset = diff_get_color(use_color, DIFF_RESET);
 513
 514         if (!cnt)
 515                 return; /* result deleted */
 516
 517         while (1) {
 518                 struct sline *sl = &sline[lno];
 519                 unsigned long hunk_end;
 520                 unsigned long rlines;
 521                 const char *hunk_comment = NULL;
 522                 unsigned long null_context = 0;
 523
 524                 while (lno <= cnt && !(sline[lno].flag & mark)) {
 525                         if (hunk_comment_line(sline[lno].bol))
 526                                 hunk_comment = sline[lno].bol;
 527                         lno++;
 528                 }
 529                 if (cnt < lno)
 530                         break;
 531                 else {
 532                         for (hunk_end = lno + 1; hunk_end <= cnt; hunk_end++)
 533                                 if (!(sline[hunk_end].flag & mark))
 534                                         break;
 535                 }
 536                 rlines = hunk_end - lno;
 537                 if (cnt < hunk_end)
 538                         rlines--; /* pointing at the last delete hunk */
 539
 540                 if (!context) {
 541                         /*
 542                          * Even when running with --unified=0, all
 543                          * lines in the hunk needs to be processed in
 544                          * the loop below in order to show the
 545                          * deletion recorded in lost_head.  However,
 546                          * we do not want to show the resulting line
 547                          * with all blank context markers in such a
 548                          * case.  Compensate.
 549                          */
 550                         unsigned long j;
 551                         for (j = lno; j < hunk_end; j++)
 552                                 if (!(sline[j].flag & (mark-1)))
 553                                         null_context++;
 554                         rlines -= null_context;
 555                 }
 556
 557                 fputs(c_frag, stdout);
 558                 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
 559                 for (i = 0; i < num_parent; i++)
 560                         show_parent_lno(sline, lno, hunk_end, i, null_context);
 561                 printf(" +%lu,%lu ", lno+1, rlines);
 562                 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
 563
 564                 if (hunk_comment) {
 565                         int comment_end = 0;
 566                         for (i = 0; i < 40; i++) {
 567                                 int ch = hunk_comment[i] & 0xff;
 568                                 if (!ch || ch == '\n')
 569                                         break;
 570                                 if (!isspace(ch))
 571                                     comment_end = i;
 572                         }
 573                         if (comment_end)
 574                                 putchar(' ');
 575                         for (i = 0; i < comment_end; i++)
 576                                 putchar(hunk_comment[i]);
 577                 }
 578
 579                 printf("%s\n", c_reset);
 580                 while (lno < hunk_end) {
 581                         struct lline *ll;
 582                         int j;
 583                         unsigned long p_mask;
 584                         sl = &sline[lno++];
 585                         ll = sl->lost_head;
 586                         while (ll) {
 587                                 fputs(c_old, stdout);
 588                                 for (j = 0; j < num_parent; j++) {
 589                                         if (ll->parent_map & (1UL<<j))
 590                                                 putchar('-');
 591                                         else
 592                                                 putchar(' ');
 593                                 }
 594                                 printf("%s%s\n", ll->line, c_reset);
 595                                 ll = ll->next;
 596                         }
 597                         if (cnt < lno)
 598                                 break;
 599                         p_mask = 1;
 600                         if (!(sl->flag & (mark-1))) {
 601                                 /*
 602                                  * This sline was here to hang the
 603                                  * lost lines in front of it.
 604                                  */
 605                                 if (!context)
 606                                         continue;
 607                                 fputs(c_plain, stdout);
 608                         }
 609                         else
 610                                 fputs(c_new, stdout);
 611                         for (j = 0; j < num_parent; j++) {
 612                                 if (p_mask & sl->flag)
 613                                         putchar('+');
 614                                 else
 615                                         putchar(' ');
 616                                 p_mask <<= 1;
 617                         }
 618                         printf("%.*s%s\n", sl->len, sl->bol, c_reset);
 619                 }
 620         }
 621 }
 622
 623 static void reuse_combine_diff(struct sline *sline, unsigned long cnt,
 624                                int i, int j)
 625 {
 626         /* We have already examined parent j and we know parent i
 627          * and parent j are the same, so reuse the combined result
 628          * of parent j for parent i.
 629          */
 630         unsigned long lno, imask, jmask;
 631         imask = (1UL<<i);
 632         jmask = (1UL<<j);
 633
 634         for (lno = 0; lno <= cnt; lno++) {
 635                 struct lline *ll = sline->lost_head;
 636                 sline->p_lno[i] = sline->p_lno[j];
 637                 while (ll) {
 638                         if (ll->parent_map & jmask)
 639                                 ll->parent_map |= imask;
 640                         ll = ll->next;
 641                 }
 642                 if (sline->flag & jmask)
 643                         sline->flag |= imask;
 644                 sline++;
 645         }
 646         /* the overall size of the file (sline[cnt]) */
 647         sline->p_lno[i] = sline->p_lno[j];
 648 }
 649
 650 static void dump_quoted_path(const char *prefix, const char *path,
 651                              const char *c_meta, const char *c_reset)
 652 {
 653         printf("%s%s", c_meta, prefix);
 654         if (quote_c_style(path, NULL, NULL, 0))
 655                 quote_c_style(path, NULL, stdout, 0);
 656         else
 657                 printf("%s", path);
 658         printf("%s\n", c_reset);
 659 }
 660
 661 static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
 662                             int dense, struct rev_info *rev)
 663 {
 664         struct diff_options *opt = &rev->diffopt;
 665         unsigned long result_size, cnt, lno;
 666         char *result, *cp;
 667         struct sline *sline; /* survived lines */
 668         int mode_differs = 0;
 669         int i, show_hunks;
 670         int working_tree_file = is_null_sha1(elem->sha1);
 671         int abbrev = opt->full_index ? 40 : DEFAULT_ABBREV;
 672         mmfile_t result_file;
 673
 674         context = opt->context;
 675         /* Read the result of merge first */
 676         if (!working_tree_file)
 677                 result = grab_blob(elem->sha1, &result_size);
 678         else {
 679                 /* Used by diff-tree to read from the working tree */
 680                 struct stat st;
 681                 int fd = -1;
 682
 683                 if (lstat(elem->path, &st) < 0)
 684                         goto deleted_file;
 685
 686                 if (S_ISLNK(st.st_mode)) {
 687                         size_t len = st.st_size;
 688                         result_size = len;
 689                         result = xmalloc(len + 1);
 690                         if (result_size != readlink(elem->path, result, len)) {
 691                                 error("readlink(%s): %s", elem->path,
 692                                       strerror(errno));
 693                                 return;
 694                         }
 695                         result[len] = 0;
 696                         elem->mode = canon_mode(st.st_mode);
 697                 }
 698                 else if (0 <= (fd = open(elem->path, O_RDONLY)) &&
 699                          !fstat(fd, &st)) {
 700                         size_t len = st.st_size;
 701                         size_t sz = 0;
 702                         int is_file, i;
 703
 704                         elem->mode = canon_mode(st.st_mode);
 705                         /* if symlinks don't work, assume symlink if all parents
 706                          * are symlinks
 707                          */
 708                         is_file = has_symlinks;
 709                         for (i = 0; !is_file && i < num_parent; i++)
 710                                 is_file = !S_ISLNK(elem->parent[i].mode);
 711                         if (!is_file)
 712                                 elem->mode = canon_mode(S_IFLNK);
 713
 714                         result_size = len;
 715                         result = xmalloc(len + 1);
 716                         while (sz < len) {
 717                                 int done = xread(fd, result+sz, len-sz);
 718                                 if (done == 0)
 719                                         break;
 720                                 if (done < 0)
 721                                         die("read error '%s'", elem->path);
 722                                 sz += done;
 723                         }
 724                         result[len] = 0;
 725                 }
 726                 else {
 727                 deleted_file:
 728                         result_size = 0;
 729                         elem->mode = 0;
 730                         result = xcalloc(1, 1);
 731                 }
 732
 733                 if (0 <= fd)
 734                         close(fd);
 735         }
 736
 737         for (cnt = 0, cp = result; cp < result + result_size; cp++) {
 738                 if (*cp == '\n')
 739                         cnt++;
 740         }
 741         if (result_size && result[result_size-1] != '\n')
 742                 cnt++; /* incomplete line */
 743
 744         sline = xcalloc(cnt+2, sizeof(*sline));
 745         sline[0].bol = result;
 746         for (lno = 0; lno <= cnt + 1; lno++) {
 747                 sline[lno].lost_tail = &sline[lno].lost_head;
 748                 sline[lno].flag = 0;
 749         }
 750         for (lno = 0, cp = result; cp < result + result_size; cp++) {
 751                 if (*cp == '\n') {
 752                         sline[lno].len = cp - sline[lno].bol;
 753                         lno++;
 754                         if (lno < cnt)
 755                                 sline[lno].bol = cp + 1;
 756                 }
 757         }
 758         if (result_size && result[result_size-1] != '\n')
 759                 sline[cnt-1].len = result_size - (sline[cnt-1].bol - result);
 760
 761         result_file.ptr = result;
 762         result_file.size = result_size;
 763
 764         /* Even p_lno[cnt+1] is valid -- that is for the end line number
 765          * for deletion hunk at the end.
 766          */
 767         sline[0].p_lno = xcalloc((cnt+2) * num_parent, sizeof(unsigned long));
 768         for (lno = 0; lno <= cnt; lno++)
 769                 sline[lno+1].p_lno = sline[lno].p_lno + num_parent;
 770
 771         for (i = 0; i < num_parent; i++) {
 772                 int j;
 773                 for (j = 0; j < i; j++) {
 774                         if (!hashcmp(elem->parent[i].sha1,
 775                                      elem->parent[j].sha1)) {
 776                                 reuse_combine_diff(sline, cnt, i, j);
 777                                 break;
 778                         }
 779                 }
 780                 if (i <= j)
 781                         combine_diff(elem->parent[i].sha1, &result_file, sline,
 782                                      cnt, i, num_parent);
 783                 if (elem->parent[i].mode != elem->mode)
 784                         mode_differs = 1;
 785         }
 786
 787         show_hunks = make_hunks(sline, cnt, num_parent, dense);
 788
 789         if (show_hunks || mode_differs || working_tree_file) {
 790                 const char *abb;
 791                 int use_color = opt->color_diff;
 792                 const char *c_meta = diff_get_color(use_color, DIFF_METAINFO);
 793                 const char *c_reset = diff_get_color(use_color, DIFF_RESET);
 794                 int added = 0;
 795                 int deleted = 0;
 796
 797                 if (rev->loginfo && !rev->no_commit_id)
 798                         show_log(rev, opt->msg_sep);
 799                 dump_quoted_path(dense ? "diff --cc " : "diff --combined ",
 800                                  elem->path, c_meta, c_reset);
 801                 printf("%sindex ", c_meta);
 802                 for (i = 0; i < num_parent; i++) {
 803                         abb = find_unique_abbrev(elem->parent[i].sha1,
 804                                                  abbrev);
 805                         printf("%s%s", i ? "," : "", abb);
 806                 }
 807                 abb = find_unique_abbrev(elem->sha1, abbrev);
 808                 printf("..%s%s\n", abb, c_reset);
 809
 810                 if (mode_differs) {
 811                         deleted = !elem->mode;
 812
 813                         /* We say it was added if nobody had it */
 814                         added = !deleted;
 815                         for (i = 0; added && i < num_parent; i++)
 816                                 if (elem->parent[i].status !=
 817                                     DIFF_STATUS_ADDED)
 818                                         added = 0;
 819                         if (added)
 820                                 printf("%snew file mode %06o",
 821                                        c_meta, elem->mode);
 822                         else {
 823                                 if (deleted)
 824                                         printf("%sdeleted file ", c_meta);
 825                                 printf("mode ");
 826                                 for (i = 0; i < num_parent; i++) {
 827                                         printf("%s%06o", i ? "," : "",
 828                                                elem->parent[i].mode);
 829                                 }
 830                                 if (elem->mode)
 831                                         printf("..%06o", elem->mode);
 832                         }
 833                         printf("%s\n", c_reset);
 834                 }
 835                 if (added)
 836                         dump_quoted_path("--- /dev/", "null", c_meta, c_reset);
 837                 else
 838                         dump_quoted_path("--- a/", elem->path, c_meta, c_reset);
 839                 if (deleted)
 840                         dump_quoted_path("+++ /dev/", "null", c_meta, c_reset);
 841                 else
 842                         dump_quoted_path("+++ b/", elem->path, c_meta, c_reset);
 843                 dump_sline(sline, cnt, num_parent, opt->color_diff);
 844         }
 845         free(result);
 846
 847         for (lno = 0; lno < cnt; lno++) {
 848                 if (sline[lno].lost_head) {
 849                         struct lline *ll = sline[lno].lost_head;
 850                         while (ll) {
 851                                 struct lline *tmp = ll;
 852                                 ll = ll->next;
 853                                 free(tmp);
 854                         }
 855                 }
 856         }
 857         free(sline[0].p_lno);
 858         free(sline);
 859 }
 860
 861 #define COLONS "::::::::::::::::::::::::::::::::"
 862
 863 static void show_raw_diff(struct combine_diff_path *p, int num_parent, struct rev_info *rev)
 864 {
 865         struct diff_options *opt = &rev->diffopt;
 866         int i, offset;
 867         const char *prefix;
 868         int line_termination, inter_name_termination;
 869
 870         line_termination = opt->line_termination;
 871         inter_name_termination = '\t';
 872         if (!line_termination)
 873                 inter_name_termination = 0;
 874
 875         if (rev->loginfo && !rev->no_commit_id)
 876                 show_log(rev, opt->msg_sep);
 877
 878         if (opt->output_format & DIFF_FORMAT_RAW) {
 879                 offset = strlen(COLONS) - num_parent;
 880                 if (offset < 0)
 881                         offset = 0;
 882                 prefix = COLONS + offset;
 883
 884                 /* Show the modes */
 885                 for (i = 0; i < num_parent; i++) {
 886                         printf("%s%06o", prefix, p->parent[i].mode);
 887                         prefix = " ";
 888                 }
 889                 printf("%s%06o", prefix, p->mode);
 890
 891                 /* Show sha1's */
 892                 for (i = 0; i < num_parent; i++)
 893                         printf(" %s", diff_unique_abbrev(p->parent[i].sha1,
 894                                                          opt->abbrev));
 895                 printf(" %s ", diff_unique_abbrev(p->sha1, opt->abbrev));
 896         }
 897
 898         if (opt->output_format & (DIFF_FORMAT_RAW | DIFF_FORMAT_NAME_STATUS)) {
 899                 for (i = 0; i < num_parent; i++)
 900                         putchar(p->parent[i].status);
 901                 putchar(inter_name_termination);
 902         }
 903
 904         if (line_termination) {
 905                 if (quote_c_style(p->path, NULL, NULL, 0))
 906                         quote_c_style(p->path, NULL, stdout, 0);
 907                 else
 908                         printf("%s", p->path);
 909                 putchar(line_termination);
 910         }
 911         else {
 912                 printf("%s%c", p->path, line_termination);
 913         }
 914 }
 915
 916 void show_combined_diff(struct combine_diff_path *p,
 917                        int num_parent,
 918                        int dense,
 919                        struct rev_info *rev)
 920 {
 921         struct diff_options *opt = &rev->diffopt;
 922         if (!p->len)
 923                 return;
 924         if (opt->output_format & (DIFF_FORMAT_RAW |
 925                                   DIFF_FORMAT_NAME |
 926                                   DIFF_FORMAT_NAME_STATUS))
 927                 show_raw_diff(p, num_parent, rev);
 928         else if (opt->output_format & DIFF_FORMAT_PATCH)
 929                 show_patch_diff(p, num_parent, dense, rev);
 930 }
 931
 932 void diff_tree_combined(const unsigned char *sha1,
 933                         const unsigned char parent[][20],
 934                         int num_parent,
 935                         int dense,
 936                         struct rev_info *rev)
 937 {
 938         struct diff_options *opt = &rev->diffopt;
 939         struct diff_options diffopts;
 940         struct combine_diff_path *p, *paths = NULL;
 941         int i, num_paths, needsep, show_log_first;
 942
 943         diffopts = *opt;
 944         diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
 945         diffopts.recursive = 1;
 946
 947         show_log_first = !!rev->loginfo && !rev->no_commit_id;
 948         needsep = 0;
 949         /* find set of paths that everybody touches */
 950         for (i = 0; i < num_parent; i++) {
 951                 /* show stat against the first parent even
 952                  * when doing combined diff.
 953                  */
 954                 int stat_opt = (opt->output_format &
 955                                 (DIFF_FORMAT_NUMSTAT|DIFF_FORMAT_DIFFSTAT));
 956                 if (i == 0 && stat_opt)
 957                         diffopts.output_format = stat_opt;
 958                 else
 959                         diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
 960                 diff_tree_sha1(parent[i], sha1, "", &diffopts);
 961                 diffcore_std(&diffopts);
 962                 paths = intersect_paths(paths, i, num_parent);
 963
 964                 if (show_log_first && i == 0) {
 965                         show_log(rev, opt->msg_sep);
 966                         if (rev->verbose_header && opt->output_format)
 967                                 putchar(opt->line_termination);
 968                 }
 969                 diff_flush(&diffopts);
 970         }
 971
 972         /* find out surviving paths */
 973         for (num_paths = 0, p = paths; p; p = p->next) {
 974                 if (p->len)
 975                         num_paths++;
 976         }
 977         if (num_paths) {
 978                 if (opt->output_format & (DIFF_FORMAT_RAW |
 979                                           DIFF_FORMAT_NAME |
 980                                           DIFF_FORMAT_NAME_STATUS)) {
 981                         for (p = paths; p; p = p->next) {
 982                                 if (p->len)
 983                                         show_raw_diff(p, num_parent, rev);
 984                         }
 985                         needsep = 1;
 986                 }
 987                 else if (opt->output_format &
 988                          (DIFF_FORMAT_NUMSTAT|DIFF_FORMAT_DIFFSTAT))
 989                         needsep = 1;
 990                 if (opt->output_format & DIFF_FORMAT_PATCH) {
 991                         if (needsep)
 992                                 putchar(opt->line_termination);
 993                         for (p = paths; p; p = p->next) {
 994                                 if (p->len)
 995                                         show_patch_diff(p, num_parent, dense,
 996                                                         rev);
 997                         }
 998                 }
 999         }
1000
1001         /* Clean things up */
1002         while (paths) {
1003                 struct combine_diff_path *tmp = paths;
1004                 paths = paths->next;
1005                 free(tmp);
1006         }
1007 }
1008
1009 void diff_tree_combined_merge(const unsigned char *sha1,
1010                              int dense, struct rev_info *rev)
1011 {
1012         int num_parent;
1013         const unsigned char (*parent)[20];
1014         struct commit *commit = lookup_commit(sha1);
1015         struct commit_list *parents;
1016
1017         /* count parents */
1018         for (parents = commit->parents, num_parent = 0;
1019              parents;
1020              parents = parents->next, num_parent++)
1021                 ; /* nothing */
1022
1023         parent = xmalloc(num_parent * sizeof(*parent));
1024         for (parents = commit->parents, num_parent = 0;
1025              parents;
1026              parents = parents->next, num_parent++)
1027                 hashcpy((unsigned char*)(parent + num_parent),
1028                         parents->item->object.sha1);
1029         diff_tree_combined(sha1, parent, num_parent, dense, rev);
1030 }