| /* |
| * Copyright (C) 2005 Junio C Hamano |
| */ |
| #include "cache.h" |
| #include "diff.h" |
| #include "diffcore.h" |
| |
| static int should_break(struct diff_filespec *src, |
| struct diff_filespec *dst, |
| int break_score, |
| int *merge_score_p) |
| { |
| /* dst is recorded as a modification of src. Are they so |
| * different that we are better off recording this as a pair |
| * of delete and create? |
| * |
| * There are two criteria used in this algorithm. For the |
| * purposes of helping later rename/copy, we take both delete |
| * and insert into account and estimate the amount of "edit". |
| * If the edit is very large, we break this pair so that |
| * rename/copy can pick the pieces up to match with other |
| * files. |
| * |
| * On the other hand, we would want to ignore inserts for the |
| * pure "complete rewrite" detection. As long as most of the |
| * existing contents were removed from the file, it is a |
| * complete rewrite, and if sizable chunk from the original |
| * still remains in the result, it is not a rewrite. It does |
| * not matter how much or how little new material is added to |
| * the file. |
| * |
| * The score we leave for such a broken filepair uses the |
| * latter definition so that later clean-up stage can find the |
| * pieces that should not have been broken according to the |
| * latter definition after rename/copy runs, and merge the |
| * broken pair that have a score lower than given criteria |
| * back together. The break operation itself happens |
| * according to the former definition. |
| * |
| * The minimum_edit parameter tells us when to break (the |
| * amount of "edit" required for us to consider breaking the |
| * pair). We leave the amount of deletion in *merge_score_p |
| * when we return. |
| * |
| * The value we return is 1 if we want the pair to be broken, |
| * or 0 if we do not. |
| */ |
| unsigned long delta_size, max_size; |
| unsigned long src_copied, literal_added, src_removed; |
| |
| *merge_score_p = 0; /* assume no deletion --- "do not break" |
| * is the default. |
| */ |
| |
| if (S_ISREG(src->mode) != S_ISREG(dst->mode)) { |
| *merge_score_p = (int)MAX_SCORE; |
| return 1; /* even their types are different */ |
| } |
| |
| if (src->oid_valid && dst->oid_valid && |
| !oidcmp(&src->oid, &dst->oid)) |
| return 0; /* they are the same */ |
| |
| if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0)) |
| return 0; /* error but caught downstream */ |
| |
| max_size = ((src->size > dst->size) ? src->size : dst->size); |
| if (max_size < MINIMUM_BREAK_SIZE) |
| return 0; /* we do not break too small filepair */ |
| |
| if (!src->size) |
| return 0; /* we do not let empty files get renamed */ |
| |
| if (diffcore_count_changes(src, dst, |
| &src->cnt_data, &dst->cnt_data, |
| 0, |
| &src_copied, &literal_added)) |
| return 0; |
| |
| /* sanity */ |
| if (src->size < src_copied) |
| src_copied = src->size; |
| if (dst->size < literal_added + src_copied) { |
| if (src_copied < dst->size) |
| literal_added = dst->size - src_copied; |
| else |
| literal_added = 0; |
| } |
| src_removed = src->size - src_copied; |
| |
| /* Compute merge-score, which is "how much is removed |
| * from the source material". The clean-up stage will |
| * merge the surviving pair together if the score is |
| * less than the minimum, after rename/copy runs. |
| */ |
| *merge_score_p = (int)(src_removed * MAX_SCORE / src->size); |
| if (*merge_score_p > break_score) |
| return 1; |
| |
| /* Extent of damage, which counts both inserts and |
| * deletes. |
| */ |
| delta_size = src_removed + literal_added; |
| if (delta_size * MAX_SCORE / max_size < break_score) |
| return 0; |
| |
| /* If you removed a lot without adding new material, that is |
| * not really a rewrite. |
| */ |
| if ((src->size * break_score < src_removed * MAX_SCORE) && |
| (literal_added * 20 < src_removed) && |
| (literal_added * 20 < src_copied)) |
| return 0; |
| |
| return 1; |
| } |
| |
| void diffcore_break(int break_score) |
| { |
| struct diff_queue_struct *q = &diff_queued_diff; |
| struct diff_queue_struct outq; |
| |
| /* When the filepair has this much edit (insert and delete), |
| * it is first considered to be a rewrite and broken into a |
| * create and delete filepair. This is to help breaking a |
| * file that had too much new stuff added, possibly from |
| * moving contents from another file, so that rename/copy can |
| * match it with the other file. |
| * |
| * int break_score; we reuse incoming parameter for this. |
| */ |
| |
| /* After a pair is broken according to break_score and |
| * subjected to rename/copy, both of them may survive intact, |
| * due to lack of suitable rename/copy peer. Or, the caller |
| * may be calling us without using rename/copy. When that |
| * happens, we merge the broken pieces back into one |
| * modification together if the pair did not have more than |
| * this much delete. For this computation, we do not take |
| * insert into account at all. If you start from a 100-line |
| * file and delete 97 lines of it, it does not matter if you |
| * add 27 lines to it to make a new 30-line file or if you add |
| * 997 lines to it to make a 1000-line file. Either way what |
| * you did was a rewrite of 97%. On the other hand, if you |
| * delete 3 lines, keeping 97 lines intact, it does not matter |
| * if you add 3 lines to it to make a new 100-line file or if |
| * you add 903 lines to it to make a new 1000-line file. |
| * Either way you did a lot of additions and not a rewrite. |
| * This merge happens to catch the latter case. A merge_score |
| * of 80% would be a good default value (a broken pair that |
| * has score lower than merge_score will be merged back |
| * together). |
| */ |
| int merge_score; |
| int i; |
| |
| /* See comment on DEFAULT_BREAK_SCORE and |
| * DEFAULT_MERGE_SCORE in diffcore.h |
| */ |
| merge_score = (break_score >> 16) & 0xFFFF; |
| break_score = (break_score & 0xFFFF); |
| |
| if (!break_score) |
| break_score = DEFAULT_BREAK_SCORE; |
| if (!merge_score) |
| merge_score = DEFAULT_MERGE_SCORE; |
| |
| DIFF_QUEUE_CLEAR(&outq); |
| |
| for (i = 0; i < q->nr; i++) { |
| struct diff_filepair *p = q->queue[i]; |
| int score; |
| |
| /* |
| * We deal only with in-place edit of blobs. |
| * We do not break anything else. |
| */ |
| if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) && |
| object_type(p->one->mode) == OBJ_BLOB && |
| object_type(p->two->mode) == OBJ_BLOB && |
| !strcmp(p->one->path, p->two->path)) { |
| if (should_break(p->one, p->two, |
| break_score, &score)) { |
| /* Split this into delete and create */ |
| struct diff_filespec *null_one, *null_two; |
| struct diff_filepair *dp; |
| |
| /* Set score to 0 for the pair that |
| * needs to be merged back together |
| * should they survive rename/copy. |
| * Also we do not want to break very |
| * small files. |
| */ |
| if (score < merge_score) |
| score = 0; |
| |
| /* deletion of one */ |
| null_one = alloc_filespec(p->one->path); |
| dp = diff_queue(&outq, p->one, null_one); |
| dp->score = score; |
| dp->broken_pair = 1; |
| |
| /* creation of two */ |
| null_two = alloc_filespec(p->two->path); |
| dp = diff_queue(&outq, null_two, p->two); |
| dp->score = score; |
| dp->broken_pair = 1; |
| |
| diff_free_filespec_blob(p->one); |
| diff_free_filespec_blob(p->two); |
| free(p); /* not diff_free_filepair(), we are |
| * reusing one and two here. |
| */ |
| continue; |
| } |
| } |
| diff_free_filespec_data(p->one); |
| diff_free_filespec_data(p->two); |
| diff_q(&outq, p); |
| } |
| free(q->queue); |
| *q = outq; |
| |
| return; |
| } |
| |
| static void merge_broken(struct diff_filepair *p, |
| struct diff_filepair *pp, |
| struct diff_queue_struct *outq) |
| { |
| /* p and pp are broken pairs we want to merge */ |
| struct diff_filepair *c = p, *d = pp, *dp; |
| if (DIFF_FILE_VALID(p->one)) { |
| /* this must be a delete half */ |
| d = p; c = pp; |
| } |
| /* Sanity check */ |
| if (!DIFF_FILE_VALID(d->one)) |
| die("internal error in merge #1"); |
| if (DIFF_FILE_VALID(d->two)) |
| die("internal error in merge #2"); |
| if (DIFF_FILE_VALID(c->one)) |
| die("internal error in merge #3"); |
| if (!DIFF_FILE_VALID(c->two)) |
| die("internal error in merge #4"); |
| |
| dp = diff_queue(outq, d->one, c->two); |
| dp->score = p->score; |
| /* |
| * We will be one extra user of the same src side of the |
| * broken pair, if it was used as the rename source for other |
| * paths elsewhere. Increment to mark that the path stays |
| * in the resulting tree. |
| */ |
| d->one->rename_used++; |
| diff_free_filespec_data(d->two); |
| diff_free_filespec_data(c->one); |
| free(d); |
| free(c); |
| } |
| |
| void diffcore_merge_broken(void) |
| { |
| struct diff_queue_struct *q = &diff_queued_diff; |
| struct diff_queue_struct outq; |
| int i, j; |
| |
| DIFF_QUEUE_CLEAR(&outq); |
| |
| for (i = 0; i < q->nr; i++) { |
| struct diff_filepair *p = q->queue[i]; |
| if (!p) |
| /* we already merged this with its peer */ |
| continue; |
| else if (p->broken_pair && |
| !strcmp(p->one->path, p->two->path)) { |
| /* If the peer also survived rename/copy, then |
| * we merge them back together. |
| */ |
| for (j = i + 1; j < q->nr; j++) { |
| struct diff_filepair *pp = q->queue[j]; |
| if (pp->broken_pair && |
| !strcmp(pp->one->path, pp->two->path) && |
| !strcmp(p->one->path, pp->two->path)) { |
| /* Peer survived. Merge them */ |
| merge_broken(p, pp, &outq); |
| q->queue[j] = NULL; |
| break; |
| } |
| } |
| if (q->nr <= j) |
| /* The peer did not survive, so we keep |
| * it in the output. |
| */ |
| diff_q(&outq, p); |
| } |
| else |
| diff_q(&outq, p); |
| } |
| free(q->queue); |
| *q = outq; |
| |
| return; |
| } |