combine-diff: add a bit more comments.
[git/git.git] / combine-diff.c
CommitLineData
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1#include "cache.h"
2#include "commit.h"
3#include "diff.h"
4#include "diffcore.h"
5#include "quote.h"
6
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7static 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
ea726d02 16static struct combine_diff_path *intersect_paths(struct combine_diff_path *curr, int n, int num_parent)
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17{
18 struct diff_queue_struct *q = &diff_queued_diff;
ea726d02 19 struct combine_diff_path *p;
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20 int i;
21
22 if (!n) {
ea726d02 23 struct combine_diff_path *list = NULL, **tail = &list;
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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
32 p = xmalloc(sizeof(*p) + len + 1 + num_parent * 20);
33 p->path = (char*) &(p->parent_sha1[num_parent][0]);
34 memcpy(p->path, path, len);
35 p->path[len] = 0;
36 p->len = len;
37 p->next = NULL;
38 memcpy(p->sha1, q->queue[i]->two->sha1, 20);
39 memcpy(p->parent_sha1[n], q->queue[i]->one->sha1, 20);
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40 *tail = p;
41 tail = &p->next;
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42 }
43 return list;
44 }
45
46 for (p = curr; p; p = p->next) {
47 int found = 0;
48 if (!p->len)
49 continue;
50 for (i = 0; i < q->nr; i++) {
51 const char *path;
52 int len;
53
54 if (uninteresting(q->queue[i]))
55 continue;
56 path = q->queue[i]->two->path;
57 len = strlen(path);
58 if (len == p->len && !memcmp(path, p->path, len)) {
59 found = 1;
60 memcpy(p->parent_sha1[n],
61 q->queue[i]->one->sha1, 20);
62 break;
63 }
64 }
65 if (!found)
66 p->len = 0;
67 }
68 return curr;
69}
70
b469d8b6 71/* Lines lost from parent */
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72struct lline {
73 struct lline *next;
74 int len;
75 unsigned long parent_map;
76 char line[FLEX_ARRAY];
77};
78
b469d8b6 79/* Lines surviving in the merge result */
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80struct sline {
81 struct lline *lost_head, **lost_tail;
82 char *bol;
83 int len;
b469d8b6
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84 /* bit 0 up to (N-1) are on if the parent does _not_
85 * have this line (i.e. we changed it).
86 * bit N is used for "interesting" lines, including context.
87 */
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88 unsigned long flag;
89};
90
91static char *grab_blob(const unsigned char *sha1, unsigned long *size)
92{
93 char *blob;
94 char type[20];
95 if (!memcmp(sha1, null_sha1, 20)) {
96 /* deleted blob */
97 *size = 0;
98 return xcalloc(1, 1);
99 }
100 blob = read_sha1_file(sha1, type, size);
101 if (strcmp(type, "blob"))
102 die("object '%s' is not a blob!", sha1_to_hex(sha1));
103 return blob;
104}
105
106#define TMPPATHLEN 50
107#define MAXLINELEN 10240
108
109static void write_to_temp_file(char *tmpfile, void *blob, unsigned long size)
110{
111 int fd = git_mkstemp(tmpfile, TMPPATHLEN, ".diff_XXXXXX");
112 if (fd < 0)
113 die("unable to create temp-file");
114 if (write(fd, blob, size) != size)
115 die("unable to write temp-file");
116 close(fd);
117}
118
119static void write_temp_blob(char *tmpfile, const unsigned char *sha1)
120{
121 unsigned long size;
122 void *blob;
123 blob = grab_blob(sha1, &size);
124 write_to_temp_file(tmpfile, blob, size);
125 free(blob);
126}
127
128static int parse_num(char **cp_p, unsigned int *num_p)
129{
130 char *cp = *cp_p;
131 unsigned int num = 0;
132 int read_some;
133
134 while ('0' <= *cp && *cp <= '9')
135 num = num * 10 + *cp++ - '0';
136 if (!(read_some = cp - *cp_p))
137 return -1;
138 *cp_p = cp;
139 *num_p = num;
140 return 0;
141}
142
143static int parse_hunk_header(char *line, int len,
144 unsigned int *ob, unsigned int *on,
145 unsigned int *nb, unsigned int *nn)
146{
147 char *cp;
148 cp = line + 4;
149 if (parse_num(&cp, ob)) {
150 bad_line:
151 return error("malformed diff output: %s", line);
152 }
153 if (*cp == ',') {
154 cp++;
155 if (parse_num(&cp, on))
156 goto bad_line;
157 }
158 else
159 *on = 1;
160 if (*cp++ != ' ' || *cp++ != '+')
161 goto bad_line;
162 if (parse_num(&cp, nb))
163 goto bad_line;
164 if (*cp == ',') {
165 cp++;
166 if (parse_num(&cp, nn))
167 goto bad_line;
168 }
169 else
170 *nn = 1;
171 return -!!memcmp(cp, " @@", 3);
172}
173
174static void append_lost(struct sline *sline, int n, const char *line)
175{
176 struct lline *lline;
177 int len = strlen(line);
178 unsigned long this_mask = (1UL<<n);
179 if (line[len-1] == '\n')
180 len--;
181
182 /* Check to see if we can squash things */
183 if (sline->lost_head) {
184 struct lline *last_one = NULL;
185 /* We cannot squash it with earlier one */
186 for (lline = sline->lost_head;
187 lline;
188 lline = lline->next)
189 if (lline->parent_map & this_mask)
190 last_one = lline;
191 lline = last_one ? last_one->next : sline->lost_head;
192 while (lline) {
193 if (lline->len == len &&
194 !memcmp(lline->line, line, len)) {
195 lline->parent_map |= this_mask;
196 return;
197 }
198 lline = lline->next;
199 }
200 }
201
202 lline = xmalloc(sizeof(*lline) + len + 1);
203 lline->len = len;
204 lline->next = NULL;
205 lline->parent_map = this_mask;
206 memcpy(lline->line, line, len);
207 lline->line[len] = 0;
5290a0f8 208 *sline->lost_tail = lline;
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209 sline->lost_tail = &lline->next;
210}
211
212static void combine_diff(const unsigned char *parent, const char *ourtmp,
213 struct sline *sline, int cnt, int n)
214{
215 FILE *in;
216 char parent_tmp[TMPPATHLEN];
217 char cmd[TMPPATHLEN * 2 + 1024];
218 char line[MAXLINELEN];
219 unsigned int lno, ob, on, nb, nn;
220 unsigned long pmask = ~(1UL << n);
221 struct sline *lost_bucket = NULL;
222
223 write_temp_blob(parent_tmp, parent);
224 sprintf(cmd, "diff --unified=0 -La/x -Lb/x '%s' '%s'",
225 parent_tmp, ourtmp);
226 in = popen(cmd, "r");
227 if (!in)
228 return;
229
230 lno = 1;
231 while (fgets(line, sizeof(line), in) != NULL) {
232 int len = strlen(line);
233 if (5 < len && !memcmp("@@ -", line, 4)) {
234 if (parse_hunk_header(line, len,
235 &ob, &on, &nb, &nn))
236 break;
237 lno = nb;
238 if (!nb) {
239 /* @@ -1,2 +0,0 @@ to remove the
240 * first two lines...
241 */
242 nb = 1;
243 }
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244 if (nn == 0)
245 lost_bucket = &sline[nb];
246 else
247 lost_bucket = &sline[nb-1];
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248 continue;
249 }
250 if (!lost_bucket)
b469d8b6 251 continue; /* not in any hunk yet */
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252 switch (line[0]) {
253 case '-':
254 append_lost(lost_bucket, n, line+1);
255 break;
256 case '+':
257 sline[lno-1].flag &= pmask;
258 lno++;
259 break;
260 }
261 }
262 fclose(in);
263 unlink(parent_tmp);
264}
265
266static unsigned long context = 3;
267static char combine_marker = '@';
268
269static int interesting(struct sline *sline, unsigned long all_mask)
270{
271 return ((sline->flag & all_mask) != all_mask || sline->lost_head);
272}
273
3ec1909f
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274static unsigned long adjust_hunk_tail(struct sline *sline,
275 unsigned long all_mask,
276 unsigned long hunk_begin,
277 unsigned long i)
278{
279 /* i points at the first uninteresting line.
280 * If the last line of the hunk was interesting
281 * only because it has some deletion, then
282 * it is not all that interesting for the
283 * purpose of giving trailing context lines.
284 */
285 if ((hunk_begin + 1 <= i) &&
286 ((sline[i-1].flag & all_mask) == all_mask))
287 i--;
288 return i;
289}
290
291static unsigned long next_interesting(struct sline *sline,
292 unsigned long mark,
293 unsigned long i,
294 unsigned long cnt,
295 int uninteresting)
296{
297 while (i < cnt)
298 if (uninteresting ?
299 !(sline[i].flag & mark) :
300 (sline[i].flag & mark))
301 return i;
302 else
303 i++;
304 return cnt;
305}
306
307static int give_context(struct sline *sline, unsigned long cnt, int num_parent)
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308{
309 unsigned long all_mask = (1UL<<num_parent) - 1;
310 unsigned long mark = (1UL<<num_parent);
311 unsigned long i;
312
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313 i = next_interesting(sline, mark, 0, cnt, 0);
314 if (cnt <= i)
315 return 0;
316
af3feefa 317 while (i < cnt) {
3ec1909f
JH
318 unsigned long j = (context < i) ? (i - context) : 0;
319 unsigned long k;
320 while (j < i)
321 sline[j++].flag |= mark;
322
323 again:
324 j = next_interesting(sline, mark, i, cnt, 1);
325 if (cnt <= j)
326 break; /* the rest are all interesting */
327
328 /* lookahead context lines */
329 k = next_interesting(sline, mark, j, cnt, 0);
330 j = adjust_hunk_tail(sline, all_mask, i, j);
331
332 if (k < j + context) {
333 /* k is interesting and [j,k) are not, but
334 * paint them interesting because the gap is small.
335 */
336 while (j < k)
af3feefa 337 sline[j++].flag |= mark;
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338 i = k;
339 goto again;
af3feefa 340 }
3ec1909f
JH
341
342 /* j is the first uninteresting line and there is
343 * no overlap beyond it within context lines.
344 */
345 i = k;
346 k = (j + context < cnt) ? j + context : cnt;
347 while (j < k)
348 sline[j++].flag |= mark;
349 }
350 return 1;
351}
352
353static int make_hunks(struct sline *sline, unsigned long cnt,
354 int num_parent, int dense)
355{
356 unsigned long all_mask = (1UL<<num_parent) - 1;
357 unsigned long mark = (1UL<<num_parent);
358 unsigned long i;
359 int has_interesting = 0;
360
361 for (i = 0; i < cnt; i++) {
362 if (interesting(&sline[i], all_mask))
363 sline[i].flag |= mark;
364 else
365 sline[i].flag &= ~mark;
af3feefa 366 }
d8f4790e 367 if (!dense)
3ec1909f 368 return give_context(sline, cnt, num_parent);
d8f4790e 369
263eee29
JH
370 /* Look at each hunk, and if we have changes from only one
371 * parent, or the changes are the same from all but one
372 * parent, mark that uninteresting.
d8f4790e
JH
373 */
374 i = 0;
375 while (i < cnt) {
3ec1909f 376 unsigned long j, hunk_begin, hunk_end;
bf1c32bd 377 unsigned long same_diff;
d8f4790e
JH
378 while (i < cnt && !(sline[i].flag & mark))
379 i++;
380 if (cnt <= i)
381 break; /* No more interesting hunks */
3ec1909f
JH
382 hunk_begin = i;
383 for (j = i + 1; j < cnt; j++) {
384 if (!(sline[j].flag & mark)) {
385 /* Look beyond the end to see if there
386 * is an interesting line after this
387 * hunk within context span.
388 */
389 unsigned long la; /* lookahead */
390 int contin = 0;
391 la = adjust_hunk_tail(sline, all_mask,
392 hunk_begin, j);
393 la = (la + context < cnt) ?
394 (la + context) : cnt;
395 while (j <= --la) {
396 if (sline[la].flag & mark) {
397 contin = 1;
398 break;
399 }
400 }
401 if (!contin)
402 break;
403 j = la;
404 }
405 }
406 hunk_end = j;
407
bf1c32bd 408 /* [i..hunk_end) are interesting. Now is it really
fd4b1d21
JH
409 * interesting? We check if there are only two versions
410 * and the result matches one of them. That is, we look
411 * at:
412 * (+) line, which records lines added to which parents;
413 * this line appears in the result.
414 * (-) line, which records from what parents the line
415 * was removed; this line does not appear in the result.
416 * then check the set of parents the result has difference
417 * from, from all lines. If there are lines that has
418 * different set of parents that the result has differences
419 * from, that means we have more than two versions.
420 *
421 * Even when we have only two versions, if the result does
422 * not match any of the parents, the it should be considered
423 * interesting. In such a case, we would have all '+' line.
424 * After passing the above "two versions" test, that would
425 * appear as "the same set of parents" to be "all parents".
d8f4790e 426 */
bf1c32bd
JH
427 same_diff = 0;
428 has_interesting = 0;
429 for (j = i; j < hunk_end && !has_interesting; j++) {
430 unsigned long this_diff = ~sline[j].flag & all_mask;
431 struct lline *ll = sline[j].lost_head;
432 if (this_diff) {
433 /* This has some changes. Is it the
434 * same as others?
435 */
436 if (!same_diff)
437 same_diff = this_diff;
438 else if (same_diff != this_diff) {
439 has_interesting = 1;
440 break;
441 }
442 }
443 while (ll && !has_interesting) {
444 /* Lost this line from these parents;
445 * who are they? Are they the same?
446 */
447 this_diff = ll->parent_map;
448 if (!same_diff)
449 same_diff = this_diff;
450 else if (same_diff != this_diff) {
451 has_interesting = 1;
452 }
453 ll = ll->next;
454 }
d8f4790e 455 }
bf1c32bd 456
fd4b1d21 457 if (!has_interesting && same_diff != all_mask) {
d8f4790e 458 /* This hunk is not that interesting after all */
3ec1909f 459 for (j = hunk_begin; j < hunk_end; j++)
d8f4790e
JH
460 sline[j].flag &= ~mark;
461 }
462 i = hunk_end;
463 }
3ec1909f
JH
464
465 has_interesting = give_context(sline, cnt, num_parent);
8828cdcb 466 return has_interesting;
af3feefa
JH
467}
468
469static void dump_sline(struct sline *sline, int cnt, int num_parent)
470{
471 unsigned long mark = (1UL<<num_parent);
472 int i;
473 int lno = 0;
474
475 while (1) {
476 struct sline *sl = &sline[lno];
477 int hunk_end;
478 while (lno < cnt && !(sline[lno].flag & mark))
479 lno++;
480 if (cnt <= lno)
481 break;
482 for (hunk_end = lno + 1; hunk_end < cnt; hunk_end++)
483 if (!(sline[hunk_end].flag & mark))
484 break;
485 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
486 printf(" +%d,%d ", lno+1, hunk_end-lno);
487 for (i = 0; i <= num_parent; i++) putchar(combine_marker);
488 putchar('\n');
489 while (lno < hunk_end) {
490 struct lline *ll;
491 int j;
492 sl = &sline[lno++];
493 ll = sl->lost_head;
494 while (ll) {
495 for (j = 0; j < num_parent; j++) {
496 if (ll->parent_map & (1UL<<j))
497 putchar('-');
498 else
499 putchar(' ');
500 }
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JH
501 puts(ll->line);
502 ll = ll->next;
503 }
504 for (j = 0; j < num_parent; j++) {
505 if ((1UL<<j) & sl->flag)
506 putchar(' ');
507 else
508 putchar('+');
509 }
e2283409 510 printf("%.*s\n", sl->len, sl->bol);
af3feefa
JH
511 }
512 }
513}
514
3c39e9bd
JH
515static void reuse_combine_diff(struct sline *sline, unsigned long cnt,
516 int i, int j)
517{
518 /* We have already examined parent j and we know parent i
519 * and parent j are the same, so reuse the combined result
520 * of parent j for parent i.
521 */
522 unsigned long lno, imask, jmask;
523 imask = (1UL<<i);
524 jmask = (1UL<<j);
525
526 for (lno = 0; lno < cnt; lno++) {
527 struct lline *ll = sline->lost_head;
528 while (ll) {
529 if (ll->parent_map & jmask)
530 ll->parent_map |= imask;
531 ll = ll->next;
532 }
533 if (!(sline->flag & jmask))
534 sline->flag &= ~imask;
535 sline++;
536 }
537}
538
ea726d02
JH
539int show_combined_diff(struct combine_diff_path *elem, int num_parent,
540 int dense, const char *header, int show_empty)
af3feefa
JH
541{
542 unsigned long size, cnt, lno;
543 char *result, *cp, *ep;
544 struct sline *sline; /* survived lines */
8828cdcb 545 int i, show_hunks, shown_header = 0;
ea726d02
JH
546 char ourtmp_buf[TMPPATHLEN];
547 char *ourtmp = ourtmp_buf;
af3feefa
JH
548
549 /* Read the result of merge first */
ea726d02
JH
550 if (memcmp(elem->sha1, null_sha1, 20)) {
551 result = grab_blob(elem->sha1, &size);
552 write_to_temp_file(ourtmp, result, size);
553 }
554 else {
555 struct stat st;
556 int fd;
557 ourtmp = elem->path;
558 if (0 <= (fd = open(ourtmp, O_RDONLY)) &&
559 !fstat(fd, &st)) {
560 int len = st.st_size;
561 int cnt = 0;
562
563 size = len;
564 result = xmalloc(len + 1);
565 while (cnt < len) {
566 int done = xread(fd, result+cnt, len-cnt);
567 if (done == 0)
568 break;
569 if (done < 0)
570 die("read error '%s'", ourtmp);
571 cnt += done;
572 }
573 result[len] = 0;
574 }
575 else {
576 /* deleted file */
577 size = 0;
578 result = xmalloc(1);
579 result[0] = 0;
580 ourtmp = "/dev/null";
581 }
582 if (0 <= fd)
583 close(fd);
584 }
af3feefa
JH
585
586 for (cnt = 0, cp = result; cp - result < size; cp++) {
587 if (*cp == '\n')
588 cnt++;
589 }
590 if (result[size-1] != '\n')
591 cnt++; /* incomplete line */
592
593 sline = xcalloc(cnt, sizeof(*sline));
594 ep = result;
595 sline[0].bol = result;
596 for (lno = 0, cp = result; cp - result < size; cp++) {
597 if (*cp == '\n') {
5290a0f8 598 sline[lno].lost_tail = &sline[lno].lost_head;
af3feefa
JH
599 sline[lno].len = cp - sline[lno].bol;
600 sline[lno].flag = (1UL<<num_parent) - 1;
601 lno++;
602 if (lno < cnt)
603 sline[lno].bol = cp + 1;
604 }
605 }
606 if (result[size-1] != '\n') {
5290a0f8 607 sline[cnt-1].lost_tail = &sline[cnt-1].lost_head;
af3feefa
JH
608 sline[cnt-1].len = size - (sline[cnt-1].bol - result);
609 sline[cnt-1].flag = (1UL<<num_parent) - 1;
610 }
611
3c39e9bd
JH
612 for (i = 0; i < num_parent; i++) {
613 int j;
614 for (j = 0; j < i; j++) {
615 if (!memcmp(elem->parent_sha1[i],
616 elem->parent_sha1[j], 20)) {
617 reuse_combine_diff(sline, cnt, i, j);
618 break;
619 }
620 }
621 if (i <= j)
622 combine_diff(elem->parent_sha1[i], ourtmp, sline,
623 cnt, i);
624 }
af3feefa 625
8828cdcb 626 show_hunks = make_hunks(sline, cnt, num_parent, dense);
af3feefa 627
8828cdcb
JH
628 if (header && (show_hunks || show_empty)) {
629 shown_header++;
630 puts(header);
631 }
632 if (show_hunks) {
633 printf("diff --%s ", dense ? "cc" : "combined");
634 if (quote_c_style(elem->path, NULL, NULL, 0))
635 quote_c_style(elem->path, NULL, stdout, 0);
636 else
637 printf("%s", elem->path);
638 putchar('\n');
823bcd6e
JH
639 printf("index ");
640 for (i = 0; i < num_parent; i++) {
641 printf("%s%s",
642 i ? ".." : "",
643 find_unique_abbrev(elem->parent_sha1[i],
644 DEFAULT_ABBREV));
645 }
646 printf("->%s\n",
647 find_unique_abbrev(elem->sha1, DEFAULT_ABBREV));
8828cdcb
JH
648 dump_sline(sline, cnt, num_parent);
649 }
ea726d02
JH
650 if (ourtmp == ourtmp_buf)
651 unlink(ourtmp);
af3feefa
JH
652 free(result);
653
654 for (i = 0; i < cnt; i++) {
655 if (sline[i].lost_head) {
656 struct lline *ll = sline[i].lost_head;
657 while (ll) {
658 struct lline *tmp = ll;
659 ll = ll->next;
660 free(tmp);
661 }
662 }
663 }
664 free(sline);
8828cdcb 665 return shown_header;
af3feefa
JH
666}
667
668int diff_tree_combined_merge(const unsigned char *sha1,
d8f4790e
JH
669 const char *header,
670 int show_empty_merge, int dense)
af3feefa
JH
671{
672 struct commit *commit = lookup_commit(sha1);
673 struct diff_options diffopts;
674 struct commit_list *parents;
ea726d02 675 struct combine_diff_path *p, *paths = NULL;
af3feefa
JH
676 int num_parent, i, num_paths;
677
678 diff_setup(&diffopts);
679 diffopts.output_format = DIFF_FORMAT_NO_OUTPUT;
680 diffopts.recursive = 1;
681
682 /* count parents */
683 for (parents = commit->parents, num_parent = 0;
684 parents;
685 parents = parents->next, num_parent++)
686 ; /* nothing */
687
688 /* find set of paths that everybody touches */
689 for (parents = commit->parents, i = 0;
690 parents;
691 parents = parents->next, i++) {
692 struct commit *parent = parents->item;
693 diff_tree_sha1(parent->object.sha1, commit->object.sha1, "",
694 &diffopts);
695 paths = intersect_paths(paths, i, num_parent);
696 diff_flush(&diffopts);
697 }
698
699 /* find out surviving paths */
700 for (num_paths = 0, p = paths; p; p = p->next) {
701 if (p->len)
702 num_paths++;
703 }
704 if (num_paths || show_empty_merge) {
af3feefa
JH
705 for (p = paths; p; p = p->next) {
706 if (!p->len)
707 continue;
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708 if (show_combined_diff(p, num_parent, dense, header,
709 show_empty_merge))
710 header = NULL;
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711 }
712 }
713
714 /* Clean things up */
715 while (paths) {
ea726d02 716 struct combine_diff_path *tmp = paths;
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717 paths = paths->next;
718 free(tmp);
719 }
720 return 0;
721}