Tag signing support

signature.go

@@ -5,6 +5,8 @@ package git
 */
 import "C"
 import (
+	"fmt"
+	"math"
 	"runtime"
 	"time"
 	"unsafe"
@@ -30,12 +32,30 @@ func newSignatureFromC(sig *C.git_signature) *Signature {
 	}
 }
 
-// Offset returns the time zone offset of v.When in minutes, which is what git wants.
-func (v *Signature) Offset() int {
-	_, offset := v.When.Zone()
+// Offset returns the time zone offset of sig.When in minutes, which is what git wants.
+func (sig *Signature) Offset() int {
+	_, offset := sig.When.Zone()
 	return offset / 60
 }
 
+// ToString creates a string representation of signature, optionally with time.
+func (sig *Signature) ToString(withTime bool) string {
+	str := sig.Name + " <" + sig.Email + ">"
+
+	if !withTime {
+		return str
+	}
+
+	offsetModulus := int(math.Abs(float64(sig.Offset())))
+
+	sign := "+"
+	if sig.Offset() < 0 {
+		sign = "-"
+	}
+
+	return str + fmt.Sprintf(" %d %s%02d%02d", sig.When.Unix(), sign, offsetModulus/60, offsetModulus%60)
+}
+
 func (sig *Signature) toC() (*C.git_signature, error) {
 	if sig == nil {
 		return nil, nil

signature_test.go

@@ -0,0 +1,25 @@
+package git
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestSignatureToString(t *testing.T) {
+	loc, err := time.LoadLocation("Europe/Moscow")
+	checkFatal(t, err)
+
+	sig := &Signature{
+		Name:  "Alice",
+		Email: "alice@example.com",
+		When:  time.Date(2022, 8, 14, 11, 22, 33, 0, loc),
+	}
+
+	fmt.Println(sig.When.Unix())
+
+	actual := sig.ToString(true)
+	expected := "Alice <alice@example.com> 1660465353 +0300"
+
+	compareStrings(t, actual, expected)
+}

tag.go

@@ -7,7 +7,9 @@ extern int _go_git_tag_foreach(git_repository *repo, void *payload);
 */
 import "C"
 import (
+	"bytes"
 	"runtime"
+	"strings"
 	"unsafe"
 )
 
@@ -99,6 +101,53 @@ func (c *TagsCollection) Create(name string, obj Objecter, tagger *Signature, me
 	return oid, nil
 }
 
+// CreateTagBuffer creates a tag and write it into a Golang-buffer.
+// libgit2 does not contain git_tag_create_buffer function.
+func (c *TagsCollection) CreateTagBuffer(name string, obj Objecter, tagger *Signature, message string) []byte {
+	buf := bytes.NewBuffer(nil)
+	buf.WriteString("object " + obj.AsObject().Id().String() + "\n")
+	buf.WriteString("type " + strings.ToLower(obj.AsObject().Type().String()) + "\n")
+	buf.WriteString("tag " + name + "\n")
+	buf.WriteString("tagger " + tagger.ToString(true) + "\n\n")
+	if !strings.HasSuffix(message, "\n") {
+		buf.WriteString(message + "\n")
+	} else {
+		buf.WriteString(message)
+	}
+
+	return buf.Bytes()
+}
+
+// CreateTagWithSignature creates a tag object from the given contents and
+// signature.
+func (c *TagsCollection) CreateTagWithSignature(
+	tagContent, signature string, force bool,
+) (*Oid, error) {
+	if !strings.HasSuffix(signature, "\n") {
+		signature += "\n"
+	}
+
+	tagContent += signature
+
+	cTagContent := C.CString(tagContent)
+	defer C.free(unsafe.Pointer(cTagContent))
+	cForce := cbool(force)
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	oid := new(Oid)
+	ret := C.git_tag_create_from_buffer(oid.toC(), c.repo.ptr, cTagContent, cForce)
+
+	runtime.KeepAlive(c)
+	runtime.KeepAlive(oid)
+	if ret < 0 {
+		return nil, MakeGitError(ret)
+	}
+
+	return oid, nil
+}
+
 func (c *TagsCollection) Remove(name string) error {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()

tag_test.go

@@ -1,9 +1,14 @@
 package git
 
 import (
+	"bytes"
 	"errors"
+	"strings"
 	"testing"
 	"time"
+
+	"golang.org/x/crypto/openpgp"
+	"golang.org/x/crypto/openpgp/packet"
 )
 
 func TestCreateTag(t *testing.T) {
@@ -26,6 +31,39 @@ func TestCreateTag(t *testing.T) {
 	compareStrings(t, commitId.String(), tag.TargetId().String())
 }
 
+func TestCreateTagWithSignature(t *testing.T) {
+	t.Parallel()
+	repo := createTestRepo(t)
+	defer cleanupTestRepo(t, repo)
+
+	commitID, _ := seedTestRepo(t, repo)
+
+	commit, err := repo.LookupCommit(commitID)
+	checkFatal(t, err)
+
+	tagContent := repo.Tags.CreateTagBuffer("v0.1.0", commit, &Signature{
+		Name:  "Alice",
+		Email: "alice@example.com",
+		When:  time.Now(),
+	}, "This is a tag")
+
+	entity, err := openpgp.NewEntity("Alice", "test comment", "alice@example.com", nil)
+	checkFatal(t, err)
+
+	pgpSignatureBuf := new(bytes.Buffer)
+	err = openpgp.ArmoredDetachSignText(pgpSignatureBuf, entity, strings.NewReader(string(tagContent)), &packet.Config{})
+	checkFatal(t, err)
+
+	tagID, err := repo.Tags.CreateTagWithSignature(string(tagContent), pgpSignatureBuf.String(), false)
+	checkFatal(t, err)
+
+	tag, err := repo.LookupTag(tagID)
+	checkFatal(t, err)
+
+	compareStrings(t, "v0.1.0", tag.Name())
+	compareStrings(t, commitID.String(), tag.TargetId().String())
+}
+
 func TestCreateTagLightweight(t *testing.T) {
 	t.Parallel()
 	repo := createTestRepo(t)