aboutsummaryrefslogblamecommitdiffstats
path: root/plumbing/object/rename.go
blob: b0c62b285b64710ab82e7291a2d496011ea9f8bc (plain) (tree)
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711


















































































































































































                                                                                                                             
                                                                          





                                                                                          
                                                                             











                                                                          
                                                      






























































































































































































































































































































































































































































































































                                                                                                                            
                                                




































































































                                                                              
package object

import (
	"errors"
	"io"
	"sort"
	"strings"

	"github.com/go-git/go-git/v5/plumbing"
	"github.com/go-git/go-git/v5/plumbing/filemode"
	"github.com/go-git/go-git/v5/utils/ioutil"
	"github.com/go-git/go-git/v5/utils/merkletrie"
)

// DetectRenames detects the renames in the given changes on two trees with
// the given options. It will return the given changes grouping additions and
// deletions into modifications when possible.
// If options is nil, the default diff tree options will be used.
func DetectRenames(
	changes Changes,
	opts *DiffTreeOptions,
) (Changes, error) {
	if opts == nil {
		opts = DefaultDiffTreeOptions
	}

	detector := &renameDetector{
		renameScore: int(opts.RenameScore),
		renameLimit: int(opts.RenameLimit),
		onlyExact:   opts.OnlyExactRenames,
	}

	for _, c := range changes {
		action, err := c.Action()
		if err != nil {
			return nil, err
		}

		switch action {
		case merkletrie.Insert:
			detector.added = append(detector.added, c)
		case merkletrie.Delete:
			detector.deleted = append(detector.deleted, c)
		default:
			detector.modified = append(detector.modified, c)
		}
	}

	return detector.detect()
}

// renameDetector will detect and resolve renames in a set of changes.
// see: https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/diff/RenameDetector.java
type renameDetector struct {
	added    []*Change
	deleted  []*Change
	modified []*Change

	renameScore int
	renameLimit int
	onlyExact   bool
}

// detectExactRenames detects matches files that were deleted with files that
// were added where the hash is the same on both. If there are multiple targets
// the one with the most similar path will be chosen as the rename and the
// rest as either deletions or additions.
func (d *renameDetector) detectExactRenames() {
	added := groupChangesByHash(d.added)
	deletes := groupChangesByHash(d.deleted)
	var uniqueAdds []*Change
	var nonUniqueAdds [][]*Change
	var addedLeft []*Change

	for _, cs := range added {
		if len(cs) == 1 {
			uniqueAdds = append(uniqueAdds, cs[0])
		} else {
			nonUniqueAdds = append(nonUniqueAdds, cs)
		}
	}

	for _, c := range uniqueAdds {
		hash := changeHash(c)
		deleted := deletes[hash]

		if len(deleted) == 1 {
			if sameMode(c, deleted[0]) {
				d.modified = append(d.modified, &Change{From: deleted[0].From, To: c.To})
				delete(deletes, hash)
			} else {
				addedLeft = append(addedLeft, c)
			}
		} else if len(deleted) > 1 {
			bestMatch := bestNameMatch(c, deleted)
			if bestMatch != nil && sameMode(c, bestMatch) {
				d.modified = append(d.modified, &Change{From: bestMatch.From, To: c.To})
				delete(deletes, hash)

				var newDeletes = make([]*Change, 0, len(deleted)-1)
				for _, d := range deleted {
					if d != bestMatch {
						newDeletes = append(newDeletes, d)
					}
				}
				deletes[hash] = newDeletes
			}
		} else {
			addedLeft = append(addedLeft, c)
		}
	}

	for _, added := range nonUniqueAdds {
		hash := changeHash(added[0])
		deleted := deletes[hash]

		if len(deleted) == 1 {
			deleted := deleted[0]
			bestMatch := bestNameMatch(deleted, added)
			if bestMatch != nil && sameMode(deleted, bestMatch) {
				d.modified = append(d.modified, &Change{From: deleted.From, To: bestMatch.To})
				delete(deletes, hash)

				for _, c := range added {
					if c != bestMatch {
						addedLeft = append(addedLeft, c)
					}
				}
			} else {
				addedLeft = append(addedLeft, added...)
			}
		} else if len(deleted) > 1 {
			maxSize := len(deleted) * len(added)
			if d.renameLimit > 0 && d.renameLimit < maxSize {
				maxSize = d.renameLimit
			}

			matrix := make(similarityMatrix, 0, maxSize)

			for delIdx, del := range deleted {
				deletedName := changeName(del)

				for addIdx, add := range added {
					addedName := changeName(add)

					score := nameSimilarityScore(addedName, deletedName)
					matrix = append(matrix, similarityPair{added: addIdx, deleted: delIdx, score: score})

					if len(matrix) >= maxSize {
						break
					}
				}

				if len(matrix) >= maxSize {
					break
				}
			}

			sort.Stable(matrix)

			usedAdds := make(map[*Change]struct{})
			usedDeletes := make(map[*Change]struct{})
			for i := len(matrix) - 1; i >= 0; i-- {
				del := deleted[matrix[i].deleted]
				add := added[matrix[i].added]

				if add == nil || del == nil {
					// it was already matched
					continue
				}

				usedAdds[add] = struct{}{}
				usedDeletes[del] = struct{}{}
				d.modified = append(d.modified, &Change{From: del.From, To: add.To})
				added[matrix[i].added] = nil
				deleted[matrix[i].deleted] = nil
			}

			for _, c := range added {
				if _, ok := usedAdds[c]; !ok && c != nil {
					addedLeft = append(addedLeft, c)
				}
			}

			var newDeletes = make([]*Change, 0, len(deleted)-len(usedDeletes))
			for _, c := range deleted {
				if _, ok := usedDeletes[c]; !ok && c != nil {
					newDeletes = append(newDeletes, c)
				}
			}
			deletes[hash] = newDeletes
		} else {
			addedLeft = append(addedLeft, added...)
		}
	}

	d.added = addedLeft
	d.deleted = nil
	for _, dels := range deletes {
		d.deleted = append(d.deleted, dels...)
	}
}

// detectContentRenames detects renames based on the similarity of the content
// in the files by building a matrix of pairs between sources and destinations
// and matching by the highest score.
// see: https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityRenameDetector.java
func (d *renameDetector) detectContentRenames() error {
	cnt := max(len(d.added), len(d.deleted))
	if d.renameLimit > 0 && cnt > d.renameLimit {
		return nil
	}

	srcs, dsts := d.deleted, d.added
	matrix, err := buildSimilarityMatrix(srcs, dsts, d.renameScore)
	if err != nil {
		return err
	}
	renames := make([]*Change, 0, min(len(matrix), len(dsts)))

	// Match rename pairs on a first come, first serve basis until
	// we have looked at everything that is above the minimum score.
	for i := len(matrix) - 1; i >= 0; i-- {
		pair := matrix[i]
		src := srcs[pair.deleted]
		dst := dsts[pair.added]

		if dst == nil || src == nil {
			// It was already matched before
			continue
		}

		renames = append(renames, &Change{From: src.From, To: dst.To})

		// Claim destination and source as matched
		dsts[pair.added] = nil
		srcs[pair.deleted] = nil
	}

	d.modified = append(d.modified, renames...)
	d.added = compactChanges(dsts)
	d.deleted = compactChanges(srcs)

	return nil
}

func (d *renameDetector) detect() (Changes, error) {
	if len(d.added) > 0 && len(d.deleted) > 0 {
		d.detectExactRenames()

		if !d.onlyExact {
			if err := d.detectContentRenames(); err != nil {
				return nil, err
			}
		}
	}

	result := make(Changes, 0, len(d.added)+len(d.deleted)+len(d.modified))
	result = append(result, d.added...)
	result = append(result, d.deleted...)
	result = append(result, d.modified...)

	sort.Stable(result)

	return result, nil
}

func bestNameMatch(change *Change, changes []*Change) *Change {
	var best *Change
	var bestScore int

	cname := changeName(change)

	for _, c := range changes {
		score := nameSimilarityScore(cname, changeName(c))
		if score > bestScore {
			bestScore = score
			best = c
		}
	}

	return best
}

func nameSimilarityScore(a, b string) int {
	aDirLen := strings.LastIndexByte(a, '/') + 1
	bDirLen := strings.LastIndexByte(b, '/') + 1

	dirMin := min(aDirLen, bDirLen)
	dirMax := max(aDirLen, bDirLen)

	var dirScoreLtr, dirScoreRtl int
	if dirMax == 0 {
		dirScoreLtr = 100
		dirScoreRtl = 100
	} else {
		var dirSim int

		for ; dirSim < dirMin; dirSim++ {
			if a[dirSim] != b[dirSim] {
				break
			}
		}

		dirScoreLtr = dirSim * 100 / dirMax

		if dirScoreLtr == 100 {
			dirScoreRtl = 100
		} else {
			for dirSim = 0; dirSim < dirMin; dirSim++ {
				if a[aDirLen-1-dirSim] != b[bDirLen-1-dirSim] {
					break
				}
			}
			dirScoreRtl = dirSim * 100 / dirMax
		}
	}

	fileMin := min(len(a)-aDirLen, len(b)-bDirLen)
	fileMax := max(len(a)-aDirLen, len(b)-bDirLen)

	fileSim := 0
	for ; fileSim < fileMin; fileSim++ {
		if a[len(a)-1-fileSim] != b[len(b)-1-fileSim] {
			break
		}
	}
	fileScore := fileSim * 100 / fileMax

	return (((dirScoreLtr + dirScoreRtl) * 25) + (fileScore * 50)) / 100
}

func changeName(c *Change) string {
	if c.To != empty {
		return c.To.Name
	}
	return c.From.Name
}

func changeHash(c *Change) plumbing.Hash {
	if c.To != empty {
		return c.To.TreeEntry.Hash
	}

	return c.From.TreeEntry.Hash
}

func changeMode(c *Change) filemode.FileMode {
	if c.To != empty {
		return c.To.TreeEntry.Mode
	}

	return c.From.TreeEntry.Mode
}

func sameMode(a, b *Change) bool {
	return changeMode(a) == changeMode(b)
}

func groupChangesByHash(changes []*Change) map[plumbing.Hash][]*Change {
	var result = make(map[plumbing.Hash][]*Change)
	for _, c := range changes {
		hash := changeHash(c)
		result[hash] = append(result[hash], c)
	}
	return result
}

type similarityMatrix []similarityPair

func (m similarityMatrix) Len() int      { return len(m) }
func (m similarityMatrix) Swap(i, j int) { m[i], m[j] = m[j], m[i] }
func (m similarityMatrix) Less(i, j int) bool {
	if m[i].score == m[j].score {
		if m[i].added == m[j].added {
			return m[i].deleted < m[j].deleted
		}
		return m[i].added < m[j].added
	}
	return m[i].score < m[j].score
}

type similarityPair struct {
	// index of the added file
	added int
	// index of the deleted file
	deleted int
	// similarity score
	score int
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func buildSimilarityMatrix(srcs, dsts []*Change, renameScore int) (similarityMatrix, error) {
	// Allocate for the worst-case scenario where every pair has a score
	// that we need to consider. We might not need that many.
	matrix := make(similarityMatrix, 0, len(srcs)*len(dsts))
	srcSizes := make([]int64, len(srcs))
	dstSizes := make([]int64, len(dsts))
	dstTooLarge := make(map[int]bool)

	// Consider each pair of files, if the score is above the minimum
	// threshold we need to record that scoring in the matrix so we can
	// later find the best matches.
outerLoop:
	for srcIdx, src := range srcs {
		if changeMode(src) != filemode.Regular {
			continue
		}

		// Declare the from file and the similarity index here to be able to
		// reuse it inside the inner loop. The reason to not initialize them
		// here is so we can skip the initialization in case they happen to
		// not be needed later. They will be initialized inside the inner
		// loop if and only if they're needed and reused in subsequent passes.
		var from *File
		var s *similarityIndex
		var err error
		for dstIdx, dst := range dsts {
			if changeMode(dst) != filemode.Regular {
				continue
			}

			if dstTooLarge[dstIdx] {
				continue
			}

			var to *File
			srcSize := srcSizes[srcIdx]
			if srcSize == 0 {
				from, _, err = src.Files()
				if err != nil {
					return nil, err
				}
				srcSize = from.Size + 1
				srcSizes[srcIdx] = srcSize
			}

			dstSize := dstSizes[dstIdx]
			if dstSize == 0 {
				_, to, err = dst.Files()
				if err != nil {
					return nil, err
				}
				dstSize = to.Size + 1
				dstSizes[dstIdx] = dstSize
			}

			min, max := srcSize, dstSize
			if dstSize < srcSize {
				min = dstSize
				max = srcSize
			}

			if int(min*100/max) < renameScore {
				// File sizes are too different to be a match
				continue
			}

			if s == nil {
				s, err = fileSimilarityIndex(from)
				if err != nil {
					if err == errIndexFull {
						continue outerLoop
					}
					return nil, err
				}
			}

			if to == nil {
				_, to, err = dst.Files()
				if err != nil {
					return nil, err
				}
			}

			di, err := fileSimilarityIndex(to)
			if err != nil {
				if err == errIndexFull {
					dstTooLarge[dstIdx] = true
				}

				return nil, err
			}

			contentScore := s.score(di, 10000)
			// The name score returns a value between 0 and 100, so we need to
			// convert it to the same range as the content score.
			nameScore := nameSimilarityScore(src.From.Name, dst.To.Name) * 100
			score := (contentScore*99 + nameScore*1) / 10000

			if score < renameScore {
				continue
			}

			matrix = append(matrix, similarityPair{added: dstIdx, deleted: srcIdx, score: score})
		}
	}

	sort.Stable(matrix)

	return matrix, nil
}

func compactChanges(changes []*Change) []*Change {
	var result []*Change
	for _, c := range changes {
		if c != nil {
			result = append(result, c)
		}
	}
	return result
}

const (
	keyShift      = 32
	maxCountValue = (1 << keyShift) - 1
)

var errIndexFull = errors.New("index is full")

// similarityIndex is an index structure of lines/blocks in one file.
// This structure can be used to compute an approximation of the similarity
// between two files.
// To save space in memory, this index uses a space efficient encoding which
// will not exceed 1MiB per instance. The index starts out at a smaller size
// (closer to 2KiB), but may grow as more distinct blocks withing the scanned
// file are discovered.
// see: https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityIndex.java
type similarityIndex struct {
	hashed uint64
	// number of non-zero entries in hashes
	numHashes int
	growAt    int
	hashes    []keyCountPair
	hashBits  int
}

func fileSimilarityIndex(f *File) (*similarityIndex, error) {
	idx := newSimilarityIndex()
	if err := idx.hash(f); err != nil {
		return nil, err
	}

	sort.Stable(keyCountPairs(idx.hashes))

	return idx, nil
}

func newSimilarityIndex() *similarityIndex {
	return &similarityIndex{
		hashBits: 8,
		hashes:   make([]keyCountPair, 1<<8),
		growAt:   shouldGrowAt(8),
	}
}

func (i *similarityIndex) hash(f *File) error {
	isBin, err := f.IsBinary()
	if err != nil {
		return err
	}

	r, err := f.Reader()
	if err != nil {
		return err
	}

	defer ioutil.CheckClose(r, &err)

	return i.hashContent(r, f.Size, isBin)
}

func (i *similarityIndex) hashContent(r io.Reader, size int64, isBin bool) error {
	var buf = make([]byte, 4096)
	var ptr, cnt int
	remaining := size

	for 0 < remaining {
		hash := 5381
		var blockHashedCnt uint64

		// Hash one line or block, whatever happens first
		n := int64(0)
		for {
			if ptr == cnt {
				ptr = 0
				var err error
				cnt, err = io.ReadFull(r, buf)
				if err != nil && err != io.ErrUnexpectedEOF {
					return err
				}

				if cnt == 0 {
					return io.EOF
				}
			}
			n++
			c := buf[ptr] & 0xff
			ptr++

			// Ignore CR in CRLF sequence if it's text
			if !isBin && c == '\r' && ptr < cnt && buf[ptr] == '\n' {
				continue
			}
			blockHashedCnt++

			if c == '\n' {
				break
			}

			hash = (hash << 5) + hash + int(c)

			if n >= 64 || n >= remaining {
				break
			}
		}
		i.hashed += blockHashedCnt
		if err := i.add(hash, blockHashedCnt); err != nil {
			return err
		}
		remaining -= n
	}

	return nil
}

// score computes the similarity score between this index and another one.
// A region of a file is defined as a line in a text file or a fixed-size
// block in a binary file. To prepare an index, each region in the file is
// hashed; the values and counts of hashes are retained in a sorted table.
// Define the similarity fraction F as the count of matching regions between
// the two files divided between the maximum count of regions in either file.
// The similarity score is F multiplied by the maxScore constant, yielding a
// range [0, maxScore]. It is defined as maxScore for the degenerate case of
// two empty files.
// The similarity score is symmetrical; i.e. a.score(b) == b.score(a).
func (i *similarityIndex) score(other *similarityIndex, maxScore int) int {
	var maxHashed = i.hashed
	if maxHashed < other.hashed {
		maxHashed = other.hashed
	}
	if maxHashed == 0 {
		return maxScore
	}

	return int(i.common(other) * uint64(maxScore) / maxHashed)
}

func (i *similarityIndex) common(dst *similarityIndex) uint64 {
	srcIdx, dstIdx := 0, 0
	if i.numHashes == 0 || dst.numHashes == 0 {
		return 0
	}

	var common uint64
	srcKey, dstKey := i.hashes[srcIdx].key(), dst.hashes[dstIdx].key()

	for {
		if srcKey == dstKey {
			srcCnt, dstCnt := i.hashes[srcIdx].count(), dst.hashes[dstIdx].count()
			if srcCnt < dstCnt {
				common += srcCnt
			} else {
				common += dstCnt
			}

			srcIdx++
			if srcIdx == len(i.hashes) {
				break
			}
			srcKey = i.hashes[srcIdx].key()

			dstIdx++
			if dstIdx == len(dst.hashes) {
				break
			}
			dstKey = dst.hashes[dstIdx].key()
		} else if srcKey < dstKey {
			// Region of src that is not in dst
			srcIdx++
			if srcIdx == len(i.hashes) {
				break
			}
			srcKey = i.hashes[srcIdx].key()
		} else {
			// Region of dst that is not in src
			dstIdx++
			if dstIdx == len(dst.hashes) {
				break
			}
			dstKey = dst.hashes[dstIdx].key()
		}
	}

	return common
}

func (i *similarityIndex) add(key int, cnt uint64) error {
	key = int(uint32(key) * 0x9e370001 >> 1)

	j := i.slot(key)
	for {
		v := i.hashes[j]
		if v == 0 {
			// It's an empty slot, so we can store it here.
			if i.growAt <= i.numHashes {
				if err := i.grow(); err != nil {
					return err
				}
				j = i.slot(key)
				continue
			}

			var err error
			i.hashes[j], err = newKeyCountPair(key, cnt)
			if err != nil {
				return err
			}
			i.numHashes++
			return nil
		} else if v.key() == key {
			// It's the same key, so increment the counter.
			var err error
			i.hashes[j], err = newKeyCountPair(key, v.count()+cnt)
			if err != nil {
				return err
			}
			return nil
		} else if j+1 >= len(i.hashes) {
			j = 0
		} else {
			j++
		}
	}
}

type keyCountPair uint64

func newKeyCountPair(key int, cnt uint64) (keyCountPair, error) {
	if cnt > maxCountValue {
		return 0, errIndexFull
	}

	return keyCountPair((uint64(key) << keyShift) | cnt), nil
}

func (p keyCountPair) key() int {
	return int(p >> keyShift)
}

func (p keyCountPair) count() uint64 {
	return uint64(p) & maxCountValue
}

func (i *similarityIndex) slot(key int) int {
	// We use 31 - hashBits because the upper bit was already forced
	// to be 0 and we want the remaining high bits to be used as the
	// table slot.
	return int(uint32(key) >> (31 - i.hashBits))
}

func shouldGrowAt(hashBits int) int {
	return (1 << hashBits) * (hashBits - 3) / hashBits
}

func (i *similarityIndex) grow() error {
	if i.hashBits == 30 {
		return errIndexFull
	}

	old := i.hashes

	i.hashBits++
	i.growAt = shouldGrowAt(i.hashBits)

	// TODO(erizocosmico): find a way to check if it will OOM and return
	// errIndexFull instead.
	i.hashes = make([]keyCountPair, 1<<i.hashBits)

	for _, v := range old {
		if v != 0 {
			j := i.slot(v.key())
			for i.hashes[j] != 0 {
				j++
				if j >= len(i.hashes) {
					j = 0
				}
			}
			i.hashes[j] = v
		}
	}

	return nil
}

type keyCountPairs []keyCountPair

func (p keyCountPairs) Len() int           { return len(p) }
func (p keyCountPairs) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
func (p keyCountPairs) Less(i, j int) bool { return p[i] < p[j] }