aboutsummaryrefslogtreecommitdiffstats
path: root/repository.go
blob: ffb61d8bf5dd357166a951d1ebcd4a749109affc (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
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
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
package git

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"gopkg.in/src-d/go-git.v4/config"
	"gopkg.in/src-d/go-git.v4/internal/revision"
	"gopkg.in/src-d/go-git.v4/plumbing"
	"gopkg.in/src-d/go-git.v4/plumbing/object"
	"gopkg.in/src-d/go-git.v4/plumbing/storer"
	"gopkg.in/src-d/go-git.v4/storage"
	"gopkg.in/src-d/go-git.v4/storage/filesystem"

	"gopkg.in/src-d/go-billy.v2"
	"gopkg.in/src-d/go-billy.v2/osfs"
)

var (
	ErrObjectNotFound          = errors.New("object not found")
	ErrInvalidReference        = errors.New("invalid reference, should be a tag or a branch")
	ErrRepositoryNotExists     = errors.New("repository not exists")
	ErrRepositoryAlreadyExists = errors.New("repository already exists")
	ErrRemoteNotFound          = errors.New("remote not found")
	ErrRemoteExists            = errors.New("remote already exists")
	ErrWorktreeNotProvided     = errors.New("worktree should be provided")
	ErrIsBareRepository        = errors.New("worktree not available in a bare repository")
)

// Repository represents a git repository
type Repository struct {
	Storer storage.Storer

	r  map[string]*Remote
	wt billy.Filesystem
}

// Init creates an empty git repository, based on the given Storer and worktree.
// The worktree Filesystem is optional, if nil a bare repository is created. If
// the given storer is not empty ErrRepositoryAlreadyExists is returned
func Init(s storage.Storer, worktree billy.Filesystem) (*Repository, error) {
	r := newRepository(s, worktree)
	_, err := r.Reference(plumbing.HEAD, false)
	switch err {
	case plumbing.ErrReferenceNotFound:
	case nil:
		return nil, ErrRepositoryAlreadyExists
	default:
		return nil, err
	}

	h := plumbing.NewSymbolicReference(plumbing.HEAD, plumbing.Master)
	if err := s.SetReference(h); err != nil {
		return nil, err
	}

	if worktree == nil {
		r.setIsBare(true)
		return r, nil
	}

	return r, setWorktreeAndStoragePaths(r, worktree)
}

func setWorktreeAndStoragePaths(r *Repository, worktree billy.Filesystem) error {
	type fsBased interface {
		Filesystem() billy.Filesystem
	}

	// .git file is only created if the storage is file based and the file
	// system is osfs.OS
	fs, isFSBased := r.Storer.(fsBased)
	if !isFSBased {
		return nil
	}

	_, isOS := fs.Filesystem().(*osfs.OS)
	if !isOS {
		return nil
	}

	if err := createDotGitFile(worktree, fs.Filesystem()); err != nil {
		return err
	}

	return setConfigWorktree(r, worktree, fs.Filesystem())
}

func createDotGitFile(worktree, storage billy.Filesystem) error {
	path, err := filepath.Rel(worktree.Base(), storage.Base())
	if err != nil {
		path = storage.Base()
	}

	if path == ".git" {
		// not needed, since the folder is the default place
		return nil
	}

	f, err := worktree.Create(".git")
	if err != nil {
		return err
	}

	defer f.Close()
	_, err = fmt.Fprintf(f, "gitdir: %s\n", path)
	return err
}

func setConfigWorktree(r *Repository, worktree, storage billy.Filesystem) error {
	path, err := filepath.Rel(storage.Base(), worktree.Base())
	if err != nil {
		path = worktree.Base()
	}

	if path == ".." {
		// not needed, since the folder is the default place
		return nil
	}

	cfg, err := r.Storer.Config()
	if err != nil {
		return err
	}

	cfg.Core.Worktree = path
	return r.Storer.SetConfig(cfg)
}

// Open opens a git repository using the given Storer and worktree filesystem,
// if the given storer is complete empty ErrRepositoryNotExists is returned.
// The worktree can be nil when the repository being opened is bare, if the
// repository is a normal one (not bare) and worktree is nil the err
// ErrWorktreeNotProvided is returned
func Open(s storage.Storer, worktree billy.Filesystem) (*Repository, error) {
	_, err := s.Reference(plumbing.HEAD)
	if err == plumbing.ErrReferenceNotFound {
		return nil, ErrRepositoryNotExists
	}

	if err != nil {
		return nil, err
	}

	cfg, err := s.Config()
	if err != nil {
		return nil, err
	}

	if !cfg.Core.IsBare && worktree == nil {
		return nil, ErrWorktreeNotProvided
	}

	return newRepository(s, worktree), nil
}

// Clone a repository into the given Storer and worktree Filesystem with the
// given options, if worktree is nil a bare repository is created. If the given
// storer is not empty ErrRepositoryAlreadyExists is returned
func Clone(s storage.Storer, worktree billy.Filesystem, o *CloneOptions) (*Repository, error) {
	r, err := Init(s, worktree)
	if err != nil {
		return nil, err
	}

	return r, r.clone(o)
}

// PlainInit create an empty git repository at the given path. isBare defines
// if the repository will have worktree (non-bare) or not (bare), if the path
// is not empty ErrRepositoryAlreadyExists is returned
func PlainInit(path string, isBare bool) (*Repository, error) {
	var wt, dot billy.Filesystem

	if isBare {
		dot = osfs.New(path)
	} else {
		wt = osfs.New(path)
		dot = wt.Dir(".git")
	}

	s, err := filesystem.NewStorage(dot)
	if err != nil {
		return nil, err
	}

	return Init(s, wt)
}

// PlainOpen opens a git repository from the given path. It detects if the
// repository is bare or a normal one. If the path doesn't contain a valid
// repository ErrRepositoryNotExists is returned
func PlainOpen(path string) (*Repository, error) {
	var wt, dot billy.Filesystem

	fs := osfs.New(path)
	if _, err := fs.Stat(".git"); err != nil {
		if !os.IsNotExist(err) {
			return nil, err
		}

		dot = fs
	} else {
		wt = fs
		dot = fs.Dir(".git")
	}

	s, err := filesystem.NewStorage(dot)
	if err != nil {
		return nil, err
	}

	return Open(s, wt)
}

// PlainClone a repository into the path with the given options, isBare defines
// if the new repository will be bare or normal. If the path is not empty
// ErrRepositoryAlreadyExists is returned
func PlainClone(path string, isBare bool, o *CloneOptions) (*Repository, error) {
	r, err := PlainInit(path, isBare)
	if err != nil {
		return nil, err
	}

	return r, r.clone(o)
}

func newRepository(s storage.Storer, worktree billy.Filesystem) *Repository {
	return &Repository{
		Storer: s,
		wt:     worktree,
		r:      make(map[string]*Remote, 0),
	}
}

// Config return the repository config
func (r *Repository) Config() (*config.Config, error) {
	return r.Storer.Config()
}

// Remote return a remote if exists
func (r *Repository) Remote(name string) (*Remote, error) {
	cfg, err := r.Storer.Config()
	if err != nil {
		return nil, err
	}

	c, ok := cfg.Remotes[name]
	if !ok {
		return nil, ErrRemoteNotFound
	}

	return newRemote(r.Storer, c), nil
}

// Remotes returns a list with all the remotes
func (r *Repository) Remotes() ([]*Remote, error) {
	cfg, err := r.Storer.Config()
	if err != nil {
		return nil, err
	}

	remotes := make([]*Remote, len(cfg.Remotes))

	var i int
	for _, c := range cfg.Remotes {
		remotes[i] = newRemote(r.Storer, c)
		i++
	}

	return remotes, nil
}

// CreateRemote creates a new remote
func (r *Repository) CreateRemote(c *config.RemoteConfig) (*Remote, error) {
	if err := c.Validate(); err != nil {
		return nil, err
	}

	remote := newRemote(r.Storer, c)

	cfg, err := r.Storer.Config()
	if err != nil {
		return nil, err
	}

	if _, ok := cfg.Remotes[c.Name]; ok {
		return nil, ErrRemoteExists
	}

	cfg.Remotes[c.Name] = c
	return remote, r.Storer.SetConfig(cfg)
}

// DeleteRemote delete a remote from the repository and delete the config
func (r *Repository) DeleteRemote(name string) error {
	cfg, err := r.Storer.Config()
	if err != nil {
		return err
	}

	if _, ok := cfg.Remotes[name]; !ok {
		return ErrRemoteNotFound
	}

	delete(cfg.Remotes, name)
	return r.Storer.SetConfig(cfg)
}

// Clone clones a remote repository
func (r *Repository) clone(o *CloneOptions) error {
	if err := o.Validate(); err != nil {
		return err
	}

	c := &config.RemoteConfig{
		Name: o.RemoteName,
		URL:  o.URL,
	}

	remote, err := r.CreateRemote(c)
	if err != nil {
		return err
	}

	remoteRefs, err := remote.fetch(&FetchOptions{
		RefSpecs: r.cloneRefSpec(o, c),
		Depth:    o.Depth,
		Auth:     o.Auth,
		Progress: o.Progress,
	})
	if err != nil {
		return err
	}

	head, err := storer.ResolveReference(remoteRefs, o.ReferenceName)
	if err != nil {
		return err
	}

	if _, err := r.updateReferences(c.Fetch, o.ReferenceName, head); err != nil {
		return err
	}

	if err := r.updateWorktree(); err != nil {
		return err
	}

	if o.RecurseSubmodules != NoRecurseSubmodules && r.wt != nil {
		if err := r.updateSubmodules(o.RecurseSubmodules); err != nil {
			return err
		}
	}

	return r.updateRemoteConfig(remote, o, c, head)
}

func (r *Repository) updateSubmodules(recursion SubmoduleRescursivity) error {
	w, err := r.Worktree()
	if err != nil {
		return err
	}

	s, err := w.Submodules()
	if err != nil {
		return err
	}

	return s.Update(&SubmoduleUpdateOptions{
		Init:              true,
		RecurseSubmodules: recursion,
	})
}

func (r *Repository) cloneRefSpec(o *CloneOptions,
	c *config.RemoteConfig) []config.RefSpec {

	if !o.SingleBranch {
		return c.Fetch
	}

	var rs string

	if o.ReferenceName == plumbing.HEAD {
		rs = fmt.Sprintf(refspecSingleBranchHEAD, c.Name)
	} else {
		rs = fmt.Sprintf(refspecSingleBranch,
			o.ReferenceName.Short(), c.Name)
	}

	return []config.RefSpec{config.RefSpec(rs)}
}

func (r *Repository) setIsBare(isBare bool) error {
	cfg, err := r.Storer.Config()
	if err != nil {
		return err
	}

	cfg.Core.IsBare = isBare
	return r.Storer.SetConfig(cfg)
}

const (
	refspecSingleBranch     = "+refs/heads/%s:refs/remotes/%s/%[1]s"
	refspecSingleBranchHEAD = "+HEAD:refs/remotes/%s/HEAD"
)

func (r *Repository) updateRemoteConfig(remote *Remote, o *CloneOptions,
	c *config.RemoteConfig, head *plumbing.Reference) error {

	if !o.SingleBranch {
		return nil
	}

	c.Fetch = []config.RefSpec{config.RefSpec(fmt.Sprintf(
		refspecSingleBranch, head.Name().Short(), c.Name,
	))}

	cfg, err := r.Storer.Config()
	if err != nil {
		return err
	}

	cfg.Remotes[c.Name] = c
	return r.Storer.SetConfig(cfg)
}

func (r *Repository) updateReferences(spec []config.RefSpec,
	headName plumbing.ReferenceName, resolvedHead *plumbing.Reference) (updated bool, err error) {

	if !resolvedHead.IsBranch() {
		// Detached HEAD mode
		head := plumbing.NewHashReference(plumbing.HEAD, resolvedHead.Hash())
		return updateReferenceStorerIfNeeded(r.Storer, head)
	}

	refs := []*plumbing.Reference{
		// Create local reference for the resolved head
		resolvedHead,
		// Create local symbolic HEAD
		plumbing.NewSymbolicReference(plumbing.HEAD, resolvedHead.Name()),
	}

	refs = append(refs, r.calculateRemoteHeadReference(spec, resolvedHead)...)

	for _, ref := range refs {
		u, err := updateReferenceStorerIfNeeded(r.Storer, ref)
		if err != nil {
			return updated, err
		}

		if u {
			updated = true
		}
	}

	return
}

func (r *Repository) calculateRemoteHeadReference(spec []config.RefSpec,
	resolvedHead *plumbing.Reference) []*plumbing.Reference {

	var refs []*plumbing.Reference

	// Create resolved HEAD reference with remote prefix if it does not
	// exist. This is needed when using single branch and HEAD.
	for _, rs := range spec {
		name := resolvedHead.Name()
		if !rs.Match(name) {
			continue
		}

		name = rs.Dst(name)
		_, err := r.Storer.Reference(name)
		if err == plumbing.ErrReferenceNotFound {
			refs = append(refs, plumbing.NewHashReference(name, resolvedHead.Hash()))
		}
	}

	return refs
}

func updateReferenceStorerIfNeeded(
	s storer.ReferenceStorer, r *plumbing.Reference) (updated bool, err error) {

	p, err := s.Reference(r.Name())
	if err != nil && err != plumbing.ErrReferenceNotFound {
		return false, err
	}

	// we use the string method to compare references, is the easiest way
	if err == plumbing.ErrReferenceNotFound || r.String() != p.String() {
		if err := s.SetReference(r); err != nil {
			return false, err
		}

		return true, nil
	}

	return false, nil
}

// Pull incorporates changes from a remote repository into the current branch.
// Returns nil if the operation is successful, NoErrAlreadyUpToDate if there are
// no changes to be fetched, or an error.
func (r *Repository) Pull(o *PullOptions) error {
	if err := o.Validate(); err != nil {
		return err
	}

	remote, err := r.Remote(o.RemoteName)
	if err != nil {
		return err
	}

	remoteRefs, err := remote.fetch(&FetchOptions{
		Depth:    o.Depth,
		Auth:     o.Auth,
		Progress: o.Progress,
	})

	updated := true
	if err == NoErrAlreadyUpToDate {
		updated = false
	} else if err != nil {
		return err
	}

	head, err := storer.ResolveReference(remoteRefs, o.ReferenceName)
	if err != nil {
		return err
	}

	refsUpdated, err := r.updateReferences(remote.c.Fetch, o.ReferenceName, head)
	if err != nil {
		return err
	}

	if refsUpdated {
		updated = refsUpdated
	}

	if !updated {
		return NoErrAlreadyUpToDate
	}

	if err := r.updateWorktree(); err != nil {
		return err
	}

	if o.RecurseSubmodules != NoRecurseSubmodules && r.wt != nil {
		if err := r.updateSubmodules(o.RecurseSubmodules); err != nil {
			return err
		}
	}

	return nil
}

func (r *Repository) updateWorktree() error {
	if r.wt == nil {
		return nil
	}

	w, err := r.Worktree()
	if err != nil {
		return err
	}

	h, err := r.Head()
	if err != nil {
		return err
	}

	return w.Checkout(h.Hash())
}

// Fetch fetches changes from a remote repository.
// Returns nil if the operation is successful, NoErrAlreadyUpToDate if there are
// no changes to be fetched, or an error.
func (r *Repository) Fetch(o *FetchOptions) error {
	if err := o.Validate(); err != nil {
		return err
	}

	remote, err := r.Remote(o.RemoteName)
	if err != nil {
		return err
	}

	return remote.Fetch(o)
}

// Push pushes changes to a remote.
func (r *Repository) Push(o *PushOptions) error {
	if err := o.Validate(); err != nil {
		return err
	}

	remote, err := r.Remote(o.RemoteName)
	if err != nil {
		return err
	}

	return remote.Push(o)
}

// Commit return a Commit with the given hash. If not found
// plumbing.ErrObjectNotFound is returned
func (r *Repository) Commit(h plumbing.Hash) (*object.Commit, error) {
	return object.GetCommit(r.Storer, h)
}

// Commits returns an unsorted CommitIter with all the commits in the repository
func (r *Repository) Commits() (*object.CommitIter, error) {
	iter, err := r.Storer.IterEncodedObjects(plumbing.CommitObject)
	if err != nil {
		return nil, err
	}

	return object.NewCommitIter(r.Storer, iter), nil
}

// Tree return a Tree with the given hash. If not found
// plumbing.ErrObjectNotFound is returned
func (r *Repository) Tree(h plumbing.Hash) (*object.Tree, error) {
	return object.GetTree(r.Storer, h)
}

// Trees returns an unsorted TreeIter with all the trees in the repository
func (r *Repository) Trees() (*object.TreeIter, error) {
	iter, err := r.Storer.IterEncodedObjects(plumbing.TreeObject)
	if err != nil {
		return nil, err
	}

	return object.NewTreeIter(r.Storer, iter), nil
}

// Blob returns a Blob with the given hash. If not found
// plumbing.ErrObjectNotFound is returne
func (r *Repository) Blob(h plumbing.Hash) (*object.Blob, error) {
	return object.GetBlob(r.Storer, h)
}

// Blobs returns an unsorted BlobIter with all the blobs in the repository
func (r *Repository) Blobs() (*object.BlobIter, error) {
	iter, err := r.Storer.IterEncodedObjects(plumbing.BlobObject)
	if err != nil {
		return nil, err
	}

	return object.NewBlobIter(r.Storer, iter), nil
}

// Tag returns a Tag with the given hash. If not found
// plumbing.ErrObjectNotFound is returned
func (r *Repository) Tag(h plumbing.Hash) (*object.Tag, error) {
	return object.GetTag(r.Storer, h)
}

// Tags returns a unsorted TagIter that can step through all of the annotated
// tags in the repository.
func (r *Repository) Tags() (*object.TagIter, error) {
	iter, err := r.Storer.IterEncodedObjects(plumbing.TagObject)
	if err != nil {
		return nil, err
	}

	return object.NewTagIter(r.Storer, iter), nil
}

// Object returns an Object with the given hash. If not found
// plumbing.ErrObjectNotFound is returned
func (r *Repository) Object(t plumbing.ObjectType, h plumbing.Hash) (object.Object, error) {
	obj, err := r.Storer.EncodedObject(t, h)
	if err != nil {
		if err == plumbing.ErrObjectNotFound {
			return nil, ErrObjectNotFound
		}

		return nil, err
	}

	return object.DecodeObject(r.Storer, obj)
}

// Objects returns an unsorted BlobIter with all the objects in the repository
func (r *Repository) Objects() (*object.ObjectIter, error) {
	iter, err := r.Storer.IterEncodedObjects(plumbing.AnyObject)
	if err != nil {
		return nil, err
	}

	return object.NewObjectIter(r.Storer, iter), nil
}

// Head returns the reference where HEAD is pointing to.
func (r *Repository) Head() (*plumbing.Reference, error) {
	return storer.ResolveReference(r.Storer, plumbing.HEAD)
}

// Reference returns the reference for a given reference name. If resolved is
// true, any symbolic reference will be resolved.
func (r *Repository) Reference(name plumbing.ReferenceName, resolved bool) (
	*plumbing.Reference, error) {

	if resolved {
		return storer.ResolveReference(r.Storer, name)
	}

	return r.Storer.Reference(name)
}

// References returns an unsorted ReferenceIter for all references.
func (r *Repository) References() (storer.ReferenceIter, error) {
	return r.Storer.IterReferences()
}

// Worktree returns a worktree based on the given fs, if nil the default
// worktree will be used.
func (r *Repository) Worktree() (*Worktree, error) {
	if r.wt == nil {
		return nil, ErrIsBareRepository
	}

	return &Worktree{r: r, fs: r.wt}, nil
}

// ResolveRevision resolves revision to corresponding hash
func (r *Repository) ResolveRevision(rev plumbing.Revision) (*plumbing.Hash, error) {
	p := revision.NewParserFromString(string(rev))

	items, err := p.Parse()

	if err != nil {
		return nil, err
	}

	var commit *object.Commit

	for _, item := range items {
		switch item.(type) {
		case revision.Ref:
			ref, err := storer.ResolveReference(r.Storer, plumbing.ReferenceName(item.(revision.Ref)))

			if err != nil {
				return &plumbing.ZeroHash, err
			}

			h := ref.Hash()

			commit, err = r.Commit(h)

			if err != nil {
				return &plumbing.ZeroHash, err
			}
		case revision.CaretPath:
			depth := item.(revision.CaretPath).Depth

			if depth == 0 {
				break
			}

			iter := commit.Parents()

			c, err := iter.Next()

			if err != nil {
				return &plumbing.ZeroHash, err
			}

			if depth == 1 {
				commit = c

				break
			}

			c, err = iter.Next()

			if err != nil {
				return &plumbing.ZeroHash, err
			}

			commit = c
		case revision.TildePath:
			for i := 0; i < item.(revision.TildePath).Depth; i++ {
				c, err := commit.Parents().Next()

				if err != nil {
					return &plumbing.ZeroHash, err
				}

				commit = c
			}
		case revision.CaretReg:
			history, err := commit.History()

			if err != nil {
				return &plumbing.ZeroHash, err
			}

			re := item.(revision.CaretReg).Regexp
			negate := item.(revision.CaretReg).Negate

			var c *object.Commit

			for i := 0; i < len(history); i++ {
				if !negate && re.MatchString(history[i].Message) {
					c = history[i]

					break
				}

				if negate && !re.MatchString(history[i].Message) {
					c = history[i]

					break
				}
			}

			if c == nil {
				return &plumbing.ZeroHash, fmt.Errorf(`No commit message match regexp : "%s"`, re.String())
			}

			commit = c
		case revision.AtDate:
			history, err := commit.History()

			if err != nil {
				return &plumbing.ZeroHash, err
			}

			date := item.(revision.AtDate).Date
			var c *object.Commit

			for i := 0; i < len(history); i++ {
				if date.Equal(history[i].Committer.When.UTC()) || history[i].Committer.When.UTC().Before(date) {
					c = history[i]

					break
				}
			}

			if c == nil {
				return &plumbing.ZeroHash, fmt.Errorf(`No commit exists prior to date "%s"`, date.String())
			}

			commit = c
		}
	}

	return &commit.Hash, nil
}