1 /*
2  * Copyright (c) 2017 Stefan Sperling <stsp@openbsd.org>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/queue.h>
18 #include <sys/stat.h>
19 
20 #include <stdio.h>
21 #include <stdlib.h>
22 #include <string.h>
23 #include <limits.h>
24 #include <sha1.h>
25 #include <zlib.h>
26 
27 #include "got_object.h"
28 #include "got_repository.h"
29 #include "got_error.h"
30 #include "got_diff.h"
31 #include "got_opentemp.h"
32 #include "got_path.h"
33 
34 #include "got_lib_diff.h"
35 #include "got_lib_delta.h"
36 #include "got_lib_inflate.h"
37 #include "got_lib_object.h"
38 
39 static const struct got_error *
40 diff_blobs(struct got_blob_object *blob1, struct got_blob_object *blob2,
41     const char *label1, const char *label2, int diff_context, FILE *outfile,
42     struct got_diff_changes *changes)
43 {
44 	struct got_diff_state ds;
45 	struct got_diff_args args;
46 	const struct got_error *err = NULL;
47 	FILE *f1 = NULL, *f2 = NULL;
48 	char hex1[SHA1_DIGEST_STRING_LENGTH];
49 	char hex2[SHA1_DIGEST_STRING_LENGTH];
50 	char *idstr1 = NULL, *idstr2 = NULL;
51 	size_t size1, size2;
52 	int res, flags = 0;
53 
54 	if (blob1) {
55 		f1 = got_opentemp();
56 		if (f1 == NULL)
57 			return got_error_from_errno("got_opentemp");
58 	} else
59 		flags |= D_EMPTY1;
60 
61 	if (blob2) {
62 		f2 = got_opentemp();
63 		if (f2 == NULL) {
64 			err = got_error_from_errno("got_opentemp");
65 			fclose(f1);
66 			return err;
67 		}
68 	} else
69 		flags |= D_EMPTY2;
70 
71 	size1 = 0;
72 	if (blob1) {
73 		idstr1 = got_object_blob_id_str(blob1, hex1, sizeof(hex1));
74 		err = got_object_blob_dump_to_file(&size1, NULL, NULL, f1,
75 		    blob1);
76 		if (err)
77 			goto done;
78 	} else
79 		idstr1 = "/dev/null";
80 
81 	size2 = 0;
82 	if (blob2) {
83 		idstr2 = got_object_blob_id_str(blob2, hex2, sizeof(hex2));
84 		err = got_object_blob_dump_to_file(&size2, NULL, NULL, f2,
85 		    blob2);
86 		if (err)
87 			goto done;
88 	} else
89 		idstr2 = "/dev/null";
90 
91 	memset(&ds, 0, sizeof(ds));
92 	/* XXX should stat buffers be passed in args instead of ds? */
93 	ds.stb1.st_mode = S_IFREG;
94 	if (blob1)
95 		ds.stb1.st_size = size1;
96 	ds.stb1.st_mtime = 0; /* XXX */
97 
98 	ds.stb2.st_mode = S_IFREG;
99 	if (blob2)
100 		ds.stb2.st_size = size2;
101 	ds.stb2.st_mtime = 0; /* XXX */
102 
103 	memset(&args, 0, sizeof(args));
104 	args.diff_format = D_UNIFIED;
105 	args.label[0] = label1 ? label1 : idstr1;
106 	args.label[1] = label2 ? label2 : idstr2;
107 	args.diff_context = diff_context;
108 	flags |= D_PROTOTYPE;
109 
110 	if (outfile) {
111 		fprintf(outfile, "blob - %s\n", idstr1);
112 		fprintf(outfile, "blob + %s\n", idstr2);
113 	}
114 	err = got_diffreg(&res, f1, f2, flags, &args, &ds, outfile, changes);
115 done:
116 	if (f1 && fclose(f1) != 0 && err == NULL)
117 		err = got_error_from_errno("fclose");
118 	if (f2 && fclose(f2) != 0 && err == NULL)
119 		err = got_error_from_errno("fclose");
120 	return err;
121 }
122 
123 const struct got_error *
124 got_diff_blob_output_unidiff(void *arg, struct got_blob_object *blob1,
125     struct got_blob_object *blob2, struct got_object_id *id1,
126     struct got_object_id *id2, const char *label1, const char *label2,
127     struct got_repository *repo)
128 {
129 	struct got_diff_blob_output_unidiff_arg *a = arg;
130 
131 	return diff_blobs(blob1, blob2, label1, label2, a->diff_context,
132 	    a->outfile, NULL);
133 }
134 
135 const struct got_error *
136 got_diff_blob(struct got_blob_object *blob1, struct got_blob_object *blob2,
137     const char *label1, const char *label2, int diff_context, FILE *outfile)
138 {
139 	return diff_blobs(blob1, blob2, label1, label2, diff_context, outfile,
140 	    NULL);
141 }
142 
143 const struct got_error *
144 got_diff_blob_file(struct got_blob_object *blob1, FILE *f2, size_t size2,
145     const char *label2, int diff_context, FILE *outfile)
146 {
147 	struct got_diff_state ds;
148 	struct got_diff_args args;
149 	const struct got_error *err = NULL;
150 	FILE *f1 = NULL;
151 	char hex1[SHA1_DIGEST_STRING_LENGTH];
152 	char *idstr1 = NULL;
153 	size_t size1;
154 	int res, flags = 0;
155 
156 	size1 = 0;
157 	if (blob1) {
158 		f1 = got_opentemp();
159 		if (f1 == NULL)
160 			return got_error_from_errno("got_opentemp");
161 		idstr1 = got_object_blob_id_str(blob1, hex1, sizeof(hex1));
162 		err = got_object_blob_dump_to_file(&size1, NULL, NULL, f1,
163 		    blob1);
164 		if (err)
165 			goto done;
166 	} else {
167 		flags |= D_EMPTY1;
168 		idstr1 = "/dev/null";
169 	}
170 
171 	if (f2 == NULL)
172 		flags |= D_EMPTY2;
173 
174 	memset(&ds, 0, sizeof(ds));
175 	/* XXX should stat buffers be passed in args instead of ds? */
176 	ds.stb1.st_mode = S_IFREG;
177 	if (blob1)
178 		ds.stb1.st_size = size1;
179 	ds.stb1.st_mtime = 0; /* XXX */
180 
181 	ds.stb2.st_mode = S_IFREG;
182 	ds.stb2.st_size = size2;
183 	ds.stb2.st_mtime = 0; /* XXX */
184 
185 	memset(&args, 0, sizeof(args));
186 	args.diff_format = D_UNIFIED;
187 	args.label[0] = label2;
188 	args.label[1] = label2;
189 	args.diff_context = diff_context;
190 	flags |= D_PROTOTYPE;
191 
192 	fprintf(outfile, "blob - %s\n", idstr1);
193 	fprintf(outfile, "file + %s\n", f2 == NULL ? "/dev/null" : label2);
194 	err = got_diffreg(&res, f1, f2, flags, &args, &ds, outfile, NULL);
195 done:
196 	if (f1 && fclose(f1) != 0 && err == NULL)
197 		err = got_error_from_errno("fclose");
198 	return err;
199 }
200 
201 const struct got_error *
202 got_diff_blob_lines_changed(struct got_diff_changes **changes,
203     struct got_blob_object *blob1, struct got_blob_object *blob2)
204 {
205 	const struct got_error *err = NULL;
206 
207 	*changes = calloc(1, sizeof(**changes));
208 	if (*changes == NULL)
209 		return got_error_from_errno("calloc");
210 	SIMPLEQ_INIT(&(*changes)->entries);
211 
212 	err = diff_blobs(blob1, blob2, NULL, NULL, 3, NULL, *changes);
213 	if (err) {
214 		got_diff_free_changes(*changes);
215 		*changes = NULL;
216 	}
217 	return err;
218 }
219 
220 void
221 got_diff_free_changes(struct got_diff_changes *changes)
222 {
223 	struct got_diff_change *change;
224 	while (!SIMPLEQ_EMPTY(&changes->entries)) {
225 		change = SIMPLEQ_FIRST(&changes->entries);
226 		SIMPLEQ_REMOVE_HEAD(&changes->entries, entry);
227 		free(change);
228 	}
229 	free(changes);
230 }
231 
232 static const struct got_error *
233 diff_added_blob(struct got_object_id *id, const char *label,
234     struct got_repository *repo, got_diff_blob_cb cb, void *cb_arg)
235 {
236 	const struct got_error *err;
237 	struct got_blob_object  *blob = NULL;
238 	struct got_object *obj = NULL;
239 
240 	err = got_object_open(&obj, repo, id);
241 	if (err)
242 		return err;
243 
244 	err = got_object_blob_open(&blob, repo, obj, 8192);
245 	if (err)
246 		goto done;
247 	err = cb(cb_arg, NULL, blob, NULL, id, NULL, label, repo);
248 done:
249 	got_object_close(obj);
250 	if (blob)
251 		got_object_blob_close(blob);
252 	return err;
253 }
254 
255 static const struct got_error *
256 diff_modified_blob(struct got_object_id *id1, struct got_object_id *id2,
257     const char *label1, const char *label2, struct got_repository *repo,
258     got_diff_blob_cb cb, void *cb_arg)
259 {
260 	const struct got_error *err;
261 	struct got_object *obj1 = NULL;
262 	struct got_object *obj2 = NULL;
263 	struct got_blob_object *blob1 = NULL;
264 	struct got_blob_object *blob2 = NULL;
265 
266 	err = got_object_open(&obj1, repo, id1);
267 	if (err)
268 		return err;
269 	if (obj1->type != GOT_OBJ_TYPE_BLOB) {
270 		err = got_error(GOT_ERR_OBJ_TYPE);
271 		goto done;
272 	}
273 
274 	err = got_object_open(&obj2, repo, id2);
275 	if (err)
276 		goto done;
277 	if (obj2->type != GOT_OBJ_TYPE_BLOB) {
278 		err = got_error(GOT_ERR_BAD_OBJ_DATA);
279 		goto done;
280 	}
281 
282 	err = got_object_blob_open(&blob1, repo, obj1, 8192);
283 	if (err)
284 		goto done;
285 
286 	err = got_object_blob_open(&blob2, repo, obj2, 8192);
287 	if (err)
288 		goto done;
289 
290 	err = cb(cb_arg, blob1, blob2, id1, id2, label1, label2, repo);
291 done:
292 	if (obj1)
293 		got_object_close(obj1);
294 	if (obj2)
295 		got_object_close(obj2);
296 	if (blob1)
297 		got_object_blob_close(blob1);
298 	if (blob2)
299 		got_object_blob_close(blob2);
300 	return err;
301 }
302 
303 static const struct got_error *
304 diff_deleted_blob(struct got_object_id *id, const char *label,
305     struct got_repository *repo, got_diff_blob_cb cb, void *cb_arg)
306 {
307 	const struct got_error *err;
308 	struct got_blob_object  *blob = NULL;
309 	struct got_object *obj = NULL;
310 
311 	err = got_object_open(&obj, repo, id);
312 	if (err)
313 		return err;
314 
315 	err = got_object_blob_open(&blob, repo, obj, 8192);
316 	if (err)
317 		goto done;
318 	err = cb(cb_arg, blob, NULL, id, NULL, label, NULL, repo);
319 done:
320 	got_object_close(obj);
321 	if (blob)
322 		got_object_blob_close(blob);
323 	return err;
324 }
325 
326 static const struct got_error *
327 diff_added_tree(struct got_object_id *id, const char *label,
328     struct got_repository *repo, got_diff_blob_cb cb, void *cb_arg,
329     int diff_content)
330 {
331 	const struct got_error *err = NULL;
332 	struct got_object *treeobj = NULL;
333 	struct got_tree_object *tree = NULL;
334 
335 	err = got_object_open(&treeobj, repo, id);
336 	if (err)
337 		goto done;
338 
339 	if (treeobj->type != GOT_OBJ_TYPE_TREE) {
340 		err = got_error(GOT_ERR_OBJ_TYPE);
341 		goto done;
342 	}
343 
344 	err = got_object_tree_open(&tree, repo, treeobj);
345 	if (err)
346 		goto done;
347 
348 	err = got_diff_tree(NULL, tree, NULL, label, repo, cb, cb_arg,
349 	    diff_content);
350 done:
351 	if (tree)
352 		got_object_tree_close(tree);
353 	if (treeobj)
354 		got_object_close(treeobj);
355 	return err;
356 }
357 
358 static const struct got_error *
359 diff_modified_tree(struct got_object_id *id1, struct got_object_id *id2,
360     const char *label1, const char *label2, struct got_repository *repo,
361     got_diff_blob_cb cb, void *cb_arg, int diff_content)
362 {
363 	const struct got_error *err;
364 	struct got_object *treeobj1 = NULL;
365 	struct got_object *treeobj2 = NULL;
366 	struct got_tree_object *tree1 = NULL;
367 	struct got_tree_object *tree2 = NULL;
368 
369 	err = got_object_open(&treeobj1, repo, id1);
370 	if (err)
371 		goto done;
372 
373 	if (treeobj1->type != GOT_OBJ_TYPE_TREE) {
374 		err = got_error(GOT_ERR_OBJ_TYPE);
375 		goto done;
376 	}
377 
378 	err = got_object_open(&treeobj2, repo, id2);
379 	if (err)
380 		goto done;
381 
382 	if (treeobj2->type != GOT_OBJ_TYPE_TREE) {
383 		err = got_error(GOT_ERR_OBJ_TYPE);
384 		goto done;
385 	}
386 
387 	err = got_object_tree_open(&tree1, repo, treeobj1);
388 	if (err)
389 		goto done;
390 
391 	err = got_object_tree_open(&tree2, repo, treeobj2);
392 	if (err)
393 		goto done;
394 
395 	err = got_diff_tree(tree1, tree2, label1, label2, repo, cb, cb_arg,
396 	    diff_content);
397 
398 done:
399 	if (tree1)
400 		got_object_tree_close(tree1);
401 	if (tree2)
402 		got_object_tree_close(tree2);
403 	if (treeobj1)
404 		got_object_close(treeobj1);
405 	if (treeobj2)
406 		got_object_close(treeobj2);
407 	return err;
408 }
409 
410 static const struct got_error *
411 diff_deleted_tree(struct got_object_id *id, const char *label,
412     struct got_repository *repo, got_diff_blob_cb cb, void *cb_arg,
413     int diff_content)
414 {
415 	const struct got_error *err;
416 	struct got_object *treeobj = NULL;
417 	struct got_tree_object *tree = NULL;
418 
419 	err = got_object_open(&treeobj, repo, id);
420 	if (err)
421 		goto done;
422 
423 	if (treeobj->type != GOT_OBJ_TYPE_TREE) {
424 		err = got_error(GOT_ERR_OBJ_TYPE);
425 		goto done;
426 	}
427 
428 	err = got_object_tree_open(&tree, repo, treeobj);
429 	if (err)
430 		goto done;
431 
432 	err = got_diff_tree(tree, NULL, label, NULL, repo, cb, cb_arg,
433 	    diff_content);
434 done:
435 	if (tree)
436 		got_object_tree_close(tree);
437 	if (treeobj)
438 		got_object_close(treeobj);
439 	return err;
440 }
441 
442 static const struct got_error *
443 diff_kind_mismatch(struct got_object_id *id1, struct got_object_id *id2,
444     const char *label1, const char *label2, struct got_repository *repo,
445     got_diff_blob_cb cb, void *cb_arg)
446 {
447 	/* XXX TODO */
448 	return NULL;
449 }
450 
451 static const struct got_error *
452 diff_entry_old_new(const struct got_tree_entry *te1,
453     const struct got_tree_entry *te2, const char *label1, const char *label2,
454     struct got_repository *repo, got_diff_blob_cb cb, void *cb_arg,
455     int diff_content)
456 {
457 	const struct got_error *err = NULL;
458 	int id_match;
459 
460 	if (te2 == NULL) {
461 		if (S_ISDIR(te1->mode))
462 			err = diff_deleted_tree(te1->id, label1, repo,
463 			    cb, cb_arg, diff_content);
464 		else {
465 			if (diff_content)
466 				err = diff_deleted_blob(te1->id, label1, repo,
467 				    cb, cb_arg);
468 			else
469 				err = cb(cb_arg, NULL, NULL, te1->id, NULL,
470 				    label1, NULL, repo);
471 		}
472 		return err;
473 	}
474 
475 	id_match = (got_object_id_cmp(te1->id, te2->id) == 0);
476 	if (S_ISDIR(te1->mode) && S_ISDIR(te2->mode)) {
477 		if (!id_match)
478 			return diff_modified_tree(te1->id, te2->id,
479 			    label1, label2, repo, cb, cb_arg, diff_content);
480 	} else if (S_ISREG(te1->mode) && S_ISREG(te2->mode)) {
481 		if (!id_match) {
482 			if (diff_content)
483 				return diff_modified_blob(te1->id, te2->id,
484 				    label1, label2, repo, cb, cb_arg);
485 			else
486 				return cb(cb_arg, NULL, NULL, te1->id,
487 				    te2->id, label1, label2, repo);
488 		}
489 	}
490 
491 	if (id_match)
492 		return NULL;
493 
494 	return diff_kind_mismatch(te1->id, te2->id, label1, label2, repo,
495 	    cb, cb_arg);
496 }
497 
498 static const struct got_error *
499 diff_entry_new_old(const struct got_tree_entry *te2,
500     const struct got_tree_entry *te1, const char *label2,
501     struct got_repository *repo, got_diff_blob_cb cb, void *cb_arg,
502     int diff_content)
503 {
504 	if (te1 != NULL) /* handled by diff_entry_old_new() */
505 		return NULL;
506 
507 	if (S_ISDIR(te2->mode))
508 		return diff_added_tree(te2->id, label2, repo, cb, cb_arg,
509 		    diff_content);
510 
511 	if (diff_content)
512 		return diff_added_blob(te2->id, label2, repo, cb, cb_arg);
513 
514 	return cb(cb_arg, NULL, NULL, NULL, te2->id, NULL, label2, repo);
515 }
516 
517 const struct got_error *
518 got_diff_tree(struct got_tree_object *tree1, struct got_tree_object *tree2,
519     const char *label1, const char *label2, struct got_repository *repo,
520     got_diff_blob_cb cb, void *cb_arg, int diff_content)
521 {
522 	const struct got_error *err = NULL;
523 	struct got_tree_entry *te1 = NULL;
524 	struct got_tree_entry *te2 = NULL;
525 	char *l1 = NULL, *l2 = NULL;
526 
527 	if (tree1) {
528 		const struct got_tree_entries *entries;
529 		entries = got_object_tree_get_entries(tree1);
530 		te1 = SIMPLEQ_FIRST(&entries->head);
531 		if (te1 && asprintf(&l1, "%s%s%s", label1, label1[0] ? "/" : "",
532 		    te1->name) == -1)
533 			return got_error_from_errno("asprintf");
534 	}
535 	if (tree2) {
536 		const struct got_tree_entries *entries;
537 		entries = got_object_tree_get_entries(tree2);
538 		te2 = SIMPLEQ_FIRST(&entries->head);
539 		if (te2 && asprintf(&l2, "%s%s%s", label2, label2[0] ? "/" : "",
540 		    te2->name) == -1)
541 			return got_error_from_errno("asprintf");
542 	}
543 
544 	do {
545 		if (te1) {
546 			const struct got_tree_entry *te = NULL;
547 			if (tree2)
548 				te = got_object_tree_find_entry(tree2,
549 				    te1->name);
550 			if (te) {
551 				free(l2);
552 				l2 = NULL;
553 				if (te && asprintf(&l2, "%s%s%s", label2,
554 				    label2[0] ? "/" : "", te->name) == -1)
555 					return
556 					    got_error_from_errno("asprintf");
557 			}
558 			err = diff_entry_old_new(te1, te, l1, l2, repo, cb,
559 			    cb_arg, diff_content);
560 			if (err)
561 				break;
562 		}
563 
564 		if (te2) {
565 			const struct got_tree_entry *te = NULL;
566 			if (tree1)
567 				te = got_object_tree_find_entry(tree1,
568 				    te2->name);
569 			free(l2);
570 			if (te) {
571 				if (asprintf(&l2, "%s%s%s", label2,
572 				    label2[0] ? "/" : "", te->name) == -1)
573 					return
574 					    got_error_from_errno("asprintf");
575 			} else {
576 				if (asprintf(&l2, "%s%s%s", label2,
577 				    label2[0] ? "/" : "", te2->name) == -1)
578 					return
579 					    got_error_from_errno("asprintf");
580 			}
581 			err = diff_entry_new_old(te2, te, l2, repo,
582 			    cb, cb_arg, diff_content);
583 			if (err)
584 				break;
585 		}
586 
587 		free(l1);
588 		l1 = NULL;
589 		if (te1) {
590 			te1 = SIMPLEQ_NEXT(te1, entry);
591 			if (te1 &&
592 			    asprintf(&l1, "%s%s%s", label1,
593 			    label1[0] ? "/" : "", te1->name) == -1)
594 				return got_error_from_errno("asprintf");
595 		}
596 		free(l2);
597 		l2 = NULL;
598 		if (te2) {
599 			te2 = SIMPLEQ_NEXT(te2, entry);
600 			if (te2 &&
601 			    asprintf(&l2, "%s%s%s", label2,
602 			        label2[0] ? "/" : "", te2->name) == -1)
603 				return got_error_from_errno("asprintf");
604 		}
605 	} while (te1 || te2);
606 
607 	return err;
608 }
609 
610 const struct got_error *
611 got_diff_objects_as_blobs(struct got_object_id *id1, struct got_object_id *id2,
612     const char *label1, const char *label2, int diff_context,
613     struct got_repository *repo, FILE *outfile)
614 {
615 	const struct got_error *err;
616 	struct got_blob_object *blob1 = NULL, *blob2 = NULL;
617 
618 	if (id1 == NULL && id2 == NULL)
619 		return got_error(GOT_ERR_NO_OBJ);
620 
621 	if (id1) {
622 		err = got_object_open_as_blob(&blob1, repo, id1, 8192);
623 		if (err)
624 			goto done;
625 	}
626 	if (id2) {
627 		err = got_object_open_as_blob(&blob2, repo, id2, 8192);
628 		if (err)
629 			goto done;
630 	}
631 	err = got_diff_blob(blob1, blob2, label1, label2, diff_context,
632 	    outfile);
633 done:
634 	if (blob1)
635 		got_object_blob_close(blob1);
636 	if (blob2)
637 		got_object_blob_close(blob2);
638 	return err;
639 }
640 
641 const struct got_error *
642 got_diff_objects_as_trees(struct got_object_id *id1, struct got_object_id *id2,
643     char *label1, char *label2, int diff_context, struct got_repository *repo,
644     FILE *outfile)
645 {
646 	const struct got_error *err;
647 	struct got_tree_object *tree1 = NULL, *tree2 = NULL;
648 	struct got_diff_blob_output_unidiff_arg arg;
649 
650 	if (id1 == NULL && id2 == NULL)
651 		return got_error(GOT_ERR_NO_OBJ);
652 
653 	if (id1) {
654 		err = got_object_open_as_tree(&tree1, repo, id1);
655 		if (err)
656 			goto done;
657 	}
658 	if (id2) {
659 		err = got_object_open_as_tree(&tree2, repo, id2);
660 		if (err)
661 			goto done;
662 	}
663 	arg.diff_context = diff_context;
664 	arg.outfile = outfile;
665 	err = got_diff_tree(tree1, tree2, label1, label2, repo,
666 	    got_diff_blob_output_unidiff, &arg, 1);
667 done:
668 	if (tree1)
669 		got_object_tree_close(tree1);
670 	if (tree2)
671 		got_object_tree_close(tree2);
672 	return err;
673 }
674 
675 const struct got_error *
676 got_diff_objects_as_commits(struct got_object_id *id1,
677     struct got_object_id *id2, int diff_context,
678     struct got_repository *repo, FILE *outfile)
679 {
680 	const struct got_error *err;
681 	struct got_commit_object *commit1 = NULL, *commit2 = NULL;
682 
683 	if (id2 == NULL)
684 		return got_error(GOT_ERR_NO_OBJ);
685 
686 	if (id1) {
687 		err = got_object_open_as_commit(&commit1, repo, id1);
688 		if (err)
689 			goto done;
690 	}
691 
692 	err = got_object_open_as_commit(&commit2, repo, id2);
693 	if (err)
694 		goto done;
695 
696 	err = got_diff_objects_as_trees(
697 	    commit1 ? got_object_commit_get_tree_id(commit1) : NULL,
698 	    got_object_commit_get_tree_id(commit2), "", "", diff_context, repo,
699 	    outfile);
700 done:
701 	if (commit1)
702 		got_object_commit_close(commit1);
703 	if (commit2)
704 		got_object_commit_close(commit2);
705 	return err;
706 }