Merge pull request #928 from vancluever/f-add-tagging-support

git: Add tagging support

6 files changed, 662 insertions, 69 deletions

diff --git a/object_walker.go b/object_walker.go
index 4cbbcca..f8b19cd 100644
--- a/object_walker.go
+++ b/object_walker.go
@@ -94,6 +94,8 @@ func (p *objectWalker) walkObjectTree(hash plumbing.Hash) error {
 				return err
 			}
 		}
+	case *object.Tag:
+		return p.walkObjectTree(obj.Target)
 	default:
 		// Error out on unhandled object types.
 		return fmt.Errorf("Unknown object %X %s %T\n", obj.ID(), obj.Type(), obj)
diff --git a/options.go b/options.go
index 7b1570f..b572770 100644
--- a/options.go
+++ b/options.go
@@ -3,6 +3,7 @@ package git
 import (
 	"errors"
 	"regexp"
+	"strings"
 
 	"golang.org/x/crypto/openpgp"
 	"gopkg.in/src-d/go-git.v4/config"
@@ -348,8 +349,9 @@ type CommitOptions struct {
 	// Parents are the parents commits for the new commit, by default when
 	// len(Parents) is zero, the hash of HEAD reference is used.
 	Parents []plumbing.Hash
-	// A key to sign the commit with. A nil value here means the commit will not
-	// be signed. The private key must be present and already decrypted.
+	// SignKey denotes a key to sign the commit with. A nil value here means the
+	// commit will not be signed. The private key must be present and already
+	// decrypted.
 	SignKey *openpgp.Entity
 }
 
@@ -377,6 +379,41 @@ func (o *CommitOptions) Validate(r *Repository) error {
 	return nil
 }
 
+var (
+	ErrMissingName    = errors.New("name field is required")
+	ErrMissingTagger  = errors.New("tagger field is required")
+	ErrMissingMessage = errors.New("message field is required")
+)
+
+// CreateTagOptions describes how a tag object should be created.
+type CreateTagOptions struct {
+	// Tagger defines the signature of the tag creator.
+	Tagger *object.Signature
+	// Message defines the annotation of the tag. It is canonicalized during
+	// validation into the format expected by git - no leading whitespace and
+	// ending in a newline.
+	Message string
+	// SignKey denotes a key to sign the tag with. A nil value here means the tag
+	// will not be signed. The private key must be present and already decrypted.
+	SignKey *openpgp.Entity
+}
+
+// Validate validates the fields and sets the default values.
+func (o *CreateTagOptions) Validate(r *Repository, hash plumbing.Hash) error {
+	if o.Tagger == nil {
+		return ErrMissingTagger
+	}
+
+	if o.Message == "" {
+		return ErrMissingMessage
+	}
+
+	// Canonicalize the message into the expected message format.
+	o.Message = strings.TrimSpace(o.Message) + "\n"
+
+	return nil
+}
+
 // ListOptions describes how a remote list should be performed.
 type ListOptions struct {
 	// Auth credentials, if required, to use with the remote repository.
diff --git a/plumbing/object/tag.go b/plumbing/object/tag.go
index 905206b..03749f9 100644
--- a/plumbing/object/tag.go
+++ b/plumbing/object/tag.go
@@ -195,13 +195,14 @@ func (t *Tag) encode(o plumbing.EncodedObject, includeSig bool) (err error) {
 		return err
 	}
 
-	if t.PGPSignature != "" && includeSig {
-		// Split all the signature lines and write with a newline at the end.
-		lines := strings.Split(t.PGPSignature, "\n")
-		for _, line := range lines {
-			if _, err = fmt.Fprintf(w, "%s\n", line); err != nil {
-				return err
-			}
+	// Note that this is highly sensitive to what it sent along in the message.
+	// Message *always* needs to end with a newline, or else the message and the
+	// signature will be concatenated into a corrupt object. Since this is a
+	// lower-level method, we assume you know what you are doing and have already
+	// done the needful on the message in the caller.
+	if includeSig {
+		if _, err = fmt.Fprint(w, t.PGPSignature); err != nil {
+			return err
 		}
 	}
 
diff --git a/repository.go b/repository.go
index bfe06a3..be1f057 100644
--- a/repository.go
+++ b/repository.go
@@ -1,15 +1,18 @@
 package git
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
 	stdioutil "io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 	"time"
 
+	"golang.org/x/crypto/openpgp"
 	"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"
@@ -32,7 +35,12 @@ var (
 	// ErrBranchExists an error stating the specified branch already exists
 	ErrBranchExists = errors.New("branch already exists")
 	// ErrBranchNotFound an error stating the specified branch does not exist
-	ErrBranchNotFound            = errors.New("branch not found")
+	ErrBranchNotFound = errors.New("branch not found")
+	// ErrTagExists an error stating the specified tag already exists
+	ErrTagExists = errors.New("tag already exists")
+	// ErrTagNotFound an error stating the specified tag does not exist
+	ErrTagNotFound = errors.New("tag not found")
+
 	ErrInvalidReference          = errors.New("invalid reference, should be a tag or a branch")
 	ErrRepositoryNotExists       = errors.New("repository does not exist")
 	ErrRepositoryAlreadyExists   = errors.New("repository already exists")
@@ -478,6 +486,139 @@ func (r *Repository) DeleteBranch(name string) error {
 	return r.Storer.SetConfig(cfg)
 }
 
+// CreateTag creates a tag. If opts is included, the tag is an annotated tag,
+// otherwise a lightweight tag is created.
+func (r *Repository) CreateTag(name string, hash plumbing.Hash, opts *CreateTagOptions) (*plumbing.Reference, error) {
+	rname := plumbing.ReferenceName(path.Join("refs", "tags", name))
+
+	_, err := r.Storer.Reference(rname)
+	switch err {
+	case nil:
+		// Tag exists, this is an error
+		return nil, ErrTagExists
+	case plumbing.ErrReferenceNotFound:
+		// Tag missing, available for creation, pass this
+	default:
+		// Some other error
+		return nil, err
+	}
+
+	var target plumbing.Hash
+	if opts != nil {
+		target, err = r.createTagObject(name, hash, opts)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		target = hash
+	}
+
+	ref := plumbing.NewHashReference(rname, target)
+	if err = r.Storer.SetReference(ref); err != nil {
+		return nil, err
+	}
+
+	return ref, nil
+}
+
+func (r *Repository) createTagObject(name string, hash plumbing.Hash, opts *CreateTagOptions) (plumbing.Hash, error) {
+	if err := opts.Validate(r, hash); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	rawobj, err := object.GetObject(r.Storer, hash)
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	tag := &object.Tag{
+		Name:       name,
+		Tagger:     *opts.Tagger,
+		Message:    opts.Message,
+		TargetType: rawobj.Type(),
+		Target:     hash,
+	}
+
+	if opts.SignKey != nil {
+		sig, err := r.buildTagSignature(tag, opts.SignKey)
+		if err != nil {
+			return plumbing.ZeroHash, err
+		}
+
+		tag.PGPSignature = sig
+	}
+
+	obj := r.Storer.NewEncodedObject()
+	if err := tag.Encode(obj); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return r.Storer.SetEncodedObject(obj)
+}
+
+func (r *Repository) buildTagSignature(tag *object.Tag, signKey *openpgp.Entity) (string, error) {
+	encoded := &plumbing.MemoryObject{}
+	if err := tag.Encode(encoded); err != nil {
+		return "", err
+	}
+
+	rdr, err := encoded.Reader()
+	if err != nil {
+		return "", err
+	}
+
+	var b bytes.Buffer
+	if err := openpgp.ArmoredDetachSign(&b, signKey, rdr, nil); err != nil {
+		return "", err
+	}
+
+	return b.String(), nil
+}
+
+// Tag returns a tag from the repository.
+//
+// If you want to check to see if the tag is an annotated tag, you can call
+// TagObject on the hash of the reference in ForEach:
+//
+//   ref, err := r.Tag("v0.1.0")
+//   if err != nil {
+//     // Handle error
+//   }
+//
+//   obj, err := r.TagObject(ref.Hash())
+//   switch err {
+//   case nil:
+//     // Tag object present
+//   case plumbing.ErrObjectNotFound:
+//     // Not a tag object
+//   default:
+//     // Some other error
+//   }
+//
+func (r *Repository) Tag(name string) (*plumbing.Reference, error) {
+	ref, err := r.Reference(plumbing.ReferenceName(path.Join("refs", "tags", name)), false)
+	if err != nil {
+		if err == plumbing.ErrReferenceNotFound {
+			// Return a friendly error for this one, versus just ReferenceNotFound.
+			return nil, ErrTagNotFound
+		}
+
+		return nil, err
+	}
+
+	return ref, nil
+}
+
+// DeleteTag deletes a tag from the repository.
+func (r *Repository) DeleteTag(name string) error {
+	_, err := r.Tag(name)
+	if err != nil {
+		return err
+	}
+
+	return r.Storer.RemoveReference(plumbing.ReferenceName(path.Join("refs", "tags", name)))
+}
+
 func (r *Repository) resolveToCommitHash(h plumbing.Hash) (plumbing.Hash, error) {
 	obj, err := r.Storer.EncodedObject(plumbing.AnyObject, h)
 	if err != nil {
@@ -839,9 +980,31 @@ func (r *Repository) Log(o *LogOptions) (object.CommitIter, error) {
 	return nil, fmt.Errorf("invalid Order=%v", o.Order)
 }
 
-// Tags returns all the References from Tags. This method returns only lightweight
-// tags. Note that not all the tags are lightweight ones. To return annotated tags
-// too, you need to call TagObjects() method.
+// Tags returns all the tag References in a repository.
+//
+// If you want to check to see if the tag is an annotated tag, you can call
+// TagObject on the hash Reference passed in through ForEach:
+//
+//   iter, err := r.Tags()
+//   if err != nil {
+//     // Handle error
+//   }
+//
+//   if err := iter.ForEach(func (ref *plumbing.Reference) error {
+//     obj, err := r.TagObject(ref.Hash())
+//     switch err {
+//     case nil:
+//       // Tag object present
+//     case plumbing.ErrObjectNotFound:
+//       // Not a tag object
+//     default:
+//       // Some other error
+//       return err
+//     }
+//   }); err != nil {
+//     // Handle outer iterator error
+//   }
+//
 func (r *Repository) Tags() (storer.ReferenceIter, error) {
 	refIter, err := r.Storer.IterReferences()
 	if err != nil {
diff --git a/repository_test.go b/repository_test.go
index 88071cf..2710d9d 100644
--- a/repository_test.go
+++ b/repository_test.go
@@ -13,6 +13,9 @@ import (
 	"testing"
 	"time"
 
+	"golang.org/x/crypto/openpgp"
+	"golang.org/x/crypto/openpgp/armor"
+	openpgperr "golang.org/x/crypto/openpgp/errors"
 	"gopkg.in/src-d/go-git.v4/config"
 	"gopkg.in/src-d/go-git.v4/plumbing"
 	"gopkg.in/src-d/go-git.v4/plumbing/cache"
@@ -1273,6 +1276,393 @@ func (s *RepositorySuite) TestTags(c *C) {
 	c.Assert(count, Equals, 5)
 }
 
+func (s *RepositorySuite) TestCreateTagLightweight(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	expected, err := r.Head()
+	c.Assert(err, IsNil)
+
+	ref, err := r.CreateTag("foobar", expected.Hash(), nil)
+	c.Assert(err, IsNil)
+	c.Assert(ref, NotNil)
+
+	actual, err := r.Tag("foobar")
+	c.Assert(err, IsNil)
+
+	c.Assert(expected.Hash(), Equals, actual.Hash())
+}
+
+func (s *RepositorySuite) TestCreateTagLightweightExists(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	expected, err := r.Head()
+	c.Assert(err, IsNil)
+
+	ref, err := r.CreateTag("lightweight-tag", expected.Hash(), nil)
+	c.Assert(ref, IsNil)
+	c.Assert(err, Equals, ErrTagExists)
+}
+
+func (s *RepositorySuite) TestCreateTagAnnotated(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	h, err := r.Head()
+	c.Assert(err, IsNil)
+
+	expectedHash := h.Hash()
+
+	ref, err := r.CreateTag("foobar", expectedHash, &CreateTagOptions{
+		Tagger:  defaultSignature(),
+		Message: "foo bar baz qux",
+	})
+	c.Assert(err, IsNil)
+
+	tag, err := r.Tag("foobar")
+	c.Assert(err, IsNil)
+
+	obj, err := r.TagObject(tag.Hash())
+	c.Assert(err, IsNil)
+
+	c.Assert(ref, DeepEquals, tag)
+	c.Assert(obj.Hash, Equals, ref.Hash())
+	c.Assert(obj.Type(), Equals, plumbing.TagObject)
+	c.Assert(obj.Target, Equals, expectedHash)
+}
+
+func (s *RepositorySuite) TestCreateTagAnnotatedBadOpts(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	h, err := r.Head()
+	c.Assert(err, IsNil)
+
+	expectedHash := h.Hash()
+
+	ref, err := r.CreateTag("foobar", expectedHash, &CreateTagOptions{
+		Message: "foo bar baz qux",
+	})
+	c.Assert(ref, IsNil)
+	c.Assert(err, Equals, ErrMissingTagger)
+
+	ref, err = r.CreateTag("foobar", expectedHash, &CreateTagOptions{
+		Tagger: defaultSignature(),
+	})
+	c.Assert(ref, IsNil)
+	c.Assert(err, Equals, ErrMissingMessage)
+}
+
+func (s *RepositorySuite) TestCreateTagAnnotatedBadHash(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	ref, err := r.CreateTag("foobar", plumbing.ZeroHash, &CreateTagOptions{
+		Tagger:  defaultSignature(),
+		Message: "foo bar baz qux",
+	})
+	c.Assert(ref, IsNil)
+	c.Assert(err, Equals, plumbing.ErrObjectNotFound)
+}
+
+func (s *RepositorySuite) TestCreateTagSigned(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	h, err := r.Head()
+	c.Assert(err, IsNil)
+
+	key := commitSignKey(c, true)
+	_, err = r.CreateTag("foobar", h.Hash(), &CreateTagOptions{
+		Tagger:  defaultSignature(),
+		Message: "foo bar baz qux",
+		SignKey: key,
+	})
+	c.Assert(err, IsNil)
+
+	tag, err := r.Tag("foobar")
+	c.Assert(err, IsNil)
+
+	obj, err := r.TagObject(tag.Hash())
+	c.Assert(err, IsNil)
+
+	// Verify the tag.
+	pks := new(bytes.Buffer)
+	pkw, err := armor.Encode(pks, openpgp.PublicKeyType, nil)
+	c.Assert(err, IsNil)
+
+	err = key.Serialize(pkw)
+	c.Assert(err, IsNil)
+	err = pkw.Close()
+	c.Assert(err, IsNil)
+
+	actual, err := obj.Verify(pks.String())
+	c.Assert(err, IsNil)
+	c.Assert(actual.PrimaryKey, DeepEquals, key.PrimaryKey)
+}
+
+func (s *RepositorySuite) TestCreateTagSignedBadKey(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	h, err := r.Head()
+	c.Assert(err, IsNil)
+
+	key := commitSignKey(c, false)
+	_, err = r.CreateTag("foobar", h.Hash(), &CreateTagOptions{
+		Tagger:  defaultSignature(),
+		Message: "foo bar baz qux",
+		SignKey: key,
+	})
+	c.Assert(err, Equals, openpgperr.InvalidArgumentError("signing key is encrypted"))
+}
+
+func (s *RepositorySuite) TestCreateTagCanonicalize(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	h, err := r.Head()
+	c.Assert(err, IsNil)
+
+	key := commitSignKey(c, true)
+	_, err = r.CreateTag("foobar", h.Hash(), &CreateTagOptions{
+		Tagger:  defaultSignature(),
+		Message: "\n\nfoo bar baz qux\n\nsome message here",
+		SignKey: key,
+	})
+	c.Assert(err, IsNil)
+
+	tag, err := r.Tag("foobar")
+	c.Assert(err, IsNil)
+
+	obj, err := r.TagObject(tag.Hash())
+	c.Assert(err, IsNil)
+
+	// Assert the new canonicalized message.
+	c.Assert(obj.Message, Equals, "foo bar baz qux\n\nsome message here\n")
+
+	// Verify the tag.
+	pks := new(bytes.Buffer)
+	pkw, err := armor.Encode(pks, openpgp.PublicKeyType, nil)
+	c.Assert(err, IsNil)
+
+	err = key.Serialize(pkw)
+	c.Assert(err, IsNil)
+	err = pkw.Close()
+	c.Assert(err, IsNil)
+
+	actual, err := obj.Verify(pks.String())
+	c.Assert(err, IsNil)
+	c.Assert(actual.PrimaryKey, DeepEquals, key.PrimaryKey)
+}
+
+func (s *RepositorySuite) TestTagLightweight(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	expected := plumbing.NewHash("f7b877701fbf855b44c0a9e86f3fdce2c298b07f")
+
+	tag, err := r.Tag("lightweight-tag")
+	c.Assert(err, IsNil)
+
+	actual := tag.Hash()
+	c.Assert(expected, Equals, actual)
+}
+
+func (s *RepositorySuite) TestTagLightweightMissingTag(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	tag, err := r.Tag("lightweight-tag-tag")
+	c.Assert(tag, IsNil)
+	c.Assert(err, Equals, ErrTagNotFound)
+}
+
+func (s *RepositorySuite) TestDeleteTag(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	err = r.DeleteTag("lightweight-tag")
+	c.Assert(err, IsNil)
+
+	_, err = r.Tag("lightweight-tag")
+	c.Assert(err, Equals, ErrTagNotFound)
+}
+
+func (s *RepositorySuite) TestDeleteTagMissingTag(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	r, _ := Init(memory.NewStorage(), nil)
+	err := r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	err = r.DeleteTag("lightweight-tag-tag")
+	c.Assert(err, Equals, ErrTagNotFound)
+}
+
+func (s *RepositorySuite) TestDeleteTagAnnotated(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	dir, err := ioutil.TempDir("", "go-git-test-deletetag-annotated")
+	c.Assert(err, IsNil)
+
+	defer os.RemoveAll(dir) // clean up
+
+	fss := filesystem.NewStorage(osfs.New(dir), cache.NewObjectLRUDefault())
+
+	r, _ := Init(fss, nil)
+	err = r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	ref, err := r.Tag("annotated-tag")
+	c.Assert(ref, NotNil)
+	c.Assert(err, IsNil)
+
+	obj, err := r.TagObject(ref.Hash())
+	c.Assert(obj, NotNil)
+	c.Assert(err, IsNil)
+
+	err = r.DeleteTag("annotated-tag")
+	c.Assert(err, IsNil)
+
+	_, err = r.Tag("annotated-tag")
+	c.Assert(err, Equals, ErrTagNotFound)
+
+	// Run a prune (and repack, to ensure that we are GCing everything regardless
+	// of the fixture in use) and try to get the tag object again.
+	//
+	// The repo needs to be re-opened after the repack.
+	err = r.Prune(PruneOptions{Handler: r.DeleteObject})
+	c.Assert(err, IsNil)
+
+	err = r.RepackObjects(&RepackConfig{})
+	c.Assert(err, IsNil)
+
+	r, err = PlainOpen(dir)
+	c.Assert(r, NotNil)
+	c.Assert(err, IsNil)
+
+	// Now check to see if the GC was effective in removing the tag object.
+	obj, err = r.TagObject(ref.Hash())
+	c.Assert(obj, IsNil)
+	c.Assert(err, Equals, plumbing.ErrObjectNotFound)
+}
+
+func (s *RepositorySuite) TestDeleteTagAnnotatedUnpacked(c *C) {
+	url := s.GetLocalRepositoryURL(
+		fixtures.ByURL("https://github.com/git-fixtures/tags.git").One(),
+	)
+
+	dir, err := ioutil.TempDir("", "go-git-test-deletetag-annotated-unpacked")
+	c.Assert(err, IsNil)
+
+	defer os.RemoveAll(dir) // clean up
+
+	fss := filesystem.NewStorage(osfs.New(dir), cache.NewObjectLRUDefault())
+
+	r, _ := Init(fss, nil)
+	err = r.clone(context.Background(), &CloneOptions{URL: url})
+	c.Assert(err, IsNil)
+
+	// Create a tag for the deletion test. This ensures that the ultimate loose
+	// object will be unpacked (as we aren't doing anything that should pack it),
+	// so that we can effectively test that a prune deletes it, without having to
+	// resort to a repack.
+	h, err := r.Head()
+	c.Assert(err, IsNil)
+
+	expectedHash := h.Hash()
+
+	ref, err := r.CreateTag("foobar", expectedHash, &CreateTagOptions{
+		Tagger:  defaultSignature(),
+		Message: "foo bar baz qux",
+	})
+	c.Assert(err, IsNil)
+
+	tag, err := r.Tag("foobar")
+	c.Assert(err, IsNil)
+
+	obj, err := r.TagObject(tag.Hash())
+	c.Assert(obj, NotNil)
+	c.Assert(err, IsNil)
+
+	err = r.DeleteTag("foobar")
+	c.Assert(err, IsNil)
+
+	_, err = r.Tag("foobar")
+	c.Assert(err, Equals, ErrTagNotFound)
+
+	// As mentioned, only run a prune. We are not testing for packed objects
+	// here.
+	err = r.Prune(PruneOptions{Handler: r.DeleteObject})
+	c.Assert(err, IsNil)
+
+	// Now check to see if the GC was effective in removing the tag object.
+	obj, err = r.TagObject(ref.Hash())
+	c.Assert(obj, IsNil)
+	c.Assert(err, Equals, plumbing.ErrObjectNotFound)
+}
+
 func (s *RepositorySuite) TestBranches(c *C) {
 	f := fixtures.ByURL("https://github.com/git-fixtures/root-references.git").One()
 	sto := filesystem.NewStorage(f.DotGit(), cache.NewObjectLRUDefault())
@@ -1544,9 +1934,9 @@ func (s *RepositorySuite) TestResolveRevisionWithErrors(c *C) {
 	c.Assert(err, IsNil)
 
 	datas := map[string]string{
-		"efs/heads/master~": "reference not found",
-		"HEAD^3":            `Revision invalid : "3" found must be 0, 1 or 2 after "^"`,
-		"HEAD^{/whatever}":  `No commit message match regexp : "whatever"`,
+		"efs/heads/master~":                        "reference not found",
+		"HEAD^3":                                   `Revision invalid : "3" found must be 0, 1 or 2 after "^"`,
+		"HEAD^{/whatever}":                         `No commit message match regexp : "whatever"`,
 		"4e1243bd22c66e76c2ba9eddc1f91394e57f9f83": "reference not found",
 		"918c48b83bd081e863dbe1b80f8998f058cd8294": `refname "918c48b83bd081e863dbe1b80f8998f058cd8294" is ambiguous`,
 	}
diff --git a/worktree_commit_test.go b/worktree_commit_test.go
index 62aae8a..da377c6 100644
--- a/worktree_commit_test.go
+++ b/worktree_commit_test.go
@@ -310,59 +310,59 @@ func commitSignKey(c *C, decrypt bool) *openpgp.Entity {
 const armoredKeyRing = `
 -----BEGIN PGP PRIVATE KEY BLOCK-----
 
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 -----END PGP PRIVATE KEY BLOCK-----
 `