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[PATCH] Add -B flag to diff-* brothers.
A new diffcore transformation, diffcore-break.c, is introduced.
When the -B flag is given, a patch that represents a complete
rewrite is broken into a deletion followed by a creation. This
makes it easier to review such a complete rewrite patch.
The -B flag takes the same syntax as the -M and -C flags to
specify the minimum amount of non-source material the resulting
file needs to have to be considered a complete rewrite, and
defaults to 99% if not specified.
As the new test t4008-diff-break-rewrite.sh demonstrates, if a
file is a complete rewrite, it is broken into a delete/create
pair, which can further be subjected to the usual rename
detection if -M or -C is used. For example, if file0 gets
completely rewritten to make it as if it were rather based on
file1 which itself disappeared, the following happens:
The original change looks like this:
file0 --> file0' (quite different from file0)
file1 --> /dev/null
After diffcore-break runs, it would become this:
file0 --> /dev/null
/dev/null --> file0'
file1 --> /dev/null
Then diffcore-rename matches them up:
file1 --> file0'
The internal score values are finer grained now. Earlier
maximum of 10000 has been raised to 60000; there is no user
visible changes but there is no reason to waste available bits.
Signed-off-by: Junio C Hamano <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>- Loading branch information
Junio C Hamano
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Linus Torvalds
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May 30, 2005
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,127 @@ | ||
| /* | ||
| * Copyright (C) 2005 Junio C Hamano | ||
| */ | ||
| #include "cache.h" | ||
| #include "diff.h" | ||
| #include "diffcore.h" | ||
| #include "delta.h" | ||
| #include "count-delta.h" | ||
|
|
||
| static int very_different(struct diff_filespec *src, | ||
| struct diff_filespec *dst, | ||
| int min_score) | ||
| { | ||
| /* 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? min_score is the minimum amount of | ||
| * new material that must exist in the dst and not in src for | ||
| * the pair to be considered a complete rewrite, and recommended | ||
| * to be set to a very high value, 99% or so. | ||
| * | ||
| * The value we return represents the amount of new material | ||
| * that is in dst and not in src. We return 0 when we do not | ||
| * want to get the filepair broken. | ||
| */ | ||
| void *delta; | ||
| unsigned long delta_size, base_size; | ||
|
|
||
| if (!S_ISREG(src->mode) || !S_ISREG(dst->mode)) | ||
| return 0; /* leave symlink rename alone */ | ||
|
|
||
| if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1)) | ||
| return 0; /* error but caught downstream */ | ||
|
|
||
| delta_size = ((src->size < dst->size) ? | ||
| (dst->size - src->size) : (src->size - dst->size)); | ||
|
|
||
| /* Notice that we use max of src and dst as the base size, | ||
| * unlike rename similarity detection. This is so that we do | ||
| * not mistake a large addition as a complete rewrite. | ||
| */ | ||
| base_size = ((src->size < dst->size) ? dst->size : src->size); | ||
|
|
||
| /* | ||
| * If file size difference is too big compared to the | ||
| * base_size, we declare this a complete rewrite. | ||
| */ | ||
| if (base_size * min_score < delta_size * MAX_SCORE) | ||
| return MAX_SCORE; | ||
|
|
||
| if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0)) | ||
| return 0; /* error but caught downstream */ | ||
|
|
||
| delta = diff_delta(src->data, src->size, | ||
| dst->data, dst->size, | ||
| &delta_size); | ||
|
|
||
| /* A delta that has a lot of literal additions would have | ||
| * big delta_size no matter what else it does. | ||
| */ | ||
| if (base_size * min_score < delta_size * MAX_SCORE) | ||
| return MAX_SCORE; | ||
|
|
||
| /* Estimate the edit size by interpreting delta. */ | ||
| delta_size = count_delta(delta, delta_size); | ||
| free(delta); | ||
| if (delta_size == UINT_MAX) | ||
| return 0; /* error in delta computation */ | ||
|
|
||
| if (base_size < delta_size) | ||
| return MAX_SCORE; | ||
|
|
||
| return delta_size * MAX_SCORE / base_size; | ||
| } | ||
|
|
||
| void diffcore_break(int min_score) | ||
| { | ||
| struct diff_queue_struct *q = &diff_queued_diff; | ||
| struct diff_queue_struct outq; | ||
| int i; | ||
|
|
||
| if (!min_score) | ||
| min_score = DEFAULT_BREAK_SCORE; | ||
|
|
||
| outq.nr = outq.alloc = 0; | ||
| outq.queue = NULL; | ||
|
|
||
| for (i = 0; i < q->nr; i++) { | ||
| struct diff_filepair *p = q->queue[i]; | ||
| int score; | ||
|
|
||
| /* We deal only with in-place edit of non directory. | ||
| * We do not break anything else. | ||
| */ | ||
| if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) && | ||
| !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) && | ||
| !strcmp(p->one->path, p->two->path)) { | ||
| score = very_different(p->one, p->two, min_score); | ||
| if (min_score <= score) { | ||
| /* Split this into delete and create */ | ||
| struct diff_filespec *null_one, *null_two; | ||
| struct diff_filepair *dp; | ||
|
|
||
| /* 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; | ||
|
|
||
| free(p); /* not diff_free_filepair(), we are | ||
| * reusing one and two here. | ||
| */ | ||
| continue; | ||
| } | ||
| } | ||
| diff_q(&outq, p); | ||
| } | ||
| free(q->queue); | ||
| *q = outq; | ||
|
|
||
| return; | ||
| } |
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