Add CreateCommitWithSignature (#782)

This change adds the wrapper for `git_commit_create_with_signature`.

Author: lhchavez

commit.go

@@ -75,40 +75,11 @@ func (c *Commit) WithSignatureUsing(f CommitSigningCallback) (*Oid, error) {
 
 // WithSignature creates a new signed commit from the given signature and signature field
 func (c *Commit) WithSignature(signature string, signatureField string) (*Oid, error) {
-	totalCommit := c.ContentToSign()
-
-	oid := new(Oid)
-
-	var csf *C.char = nil
-	if signatureField != "" {
-		csf = C.CString(signatureField)
-		defer C.free(unsafe.Pointer(csf))
-	}
-
-	runtime.LockOSThread()
-	defer runtime.UnlockOSThread()
-
-	cTotalCommit := C.CString(totalCommit)
-	cSignature := C.CString(signature)
-	defer C.free(unsafe.Pointer(cTotalCommit))
-	defer C.free(unsafe.Pointer(cSignature))
-
-	ret := C.git_commit_create_with_signature(
-		oid.toC(),
-		c.Owner().ptr,
-		cTotalCommit,
-		cSignature,
-		csf,
+	return c.Owner().CreateCommitWithSignature(
+		c.ContentToSign(),
+		signature,
+		signatureField,
 	)
-
-	runtime.KeepAlive(c)
-	runtime.KeepAlive(oid)
-
-	if ret < 0 {
-		return nil, MakeGitError(ret)
-	}
-
-	return oid, nil
 }
 
 func (c *Commit) ExtractSignature() (string, string, error) {

repository.go

@@ -485,6 +485,39 @@ func (v *Repository) CreateCommit(
 	return oid, nil
 }
 
+// CreateCommitWithSignature creates a commit object from the given contents and
+// signature.
+func (v *Repository) CreateCommitWithSignature(
+	commitContent, signature, signatureField string,
+) (*Oid, error) {
+	cCommitContent := C.CString(commitContent)
+	defer C.free(unsafe.Pointer(cCommitContent))
+	var cSignature *C.char
+	if signature != "" {
+		cSignature = C.CString(string(signature))
+		defer C.free(unsafe.Pointer(cSignature))
+	}
+	var cSignatureField *C.char
+	if signatureField != "" {
+		cSignatureField = C.CString(string(signatureField))
+		defer C.free(unsafe.Pointer(cSignatureField))
+	}
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	oid := new(Oid)
+	ret := C.git_commit_create_with_signature(oid.toC(), v.ptr, cCommitContent, cSignature, cSignatureField)
+
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(oid)
+	if ret < 0 {
+		return nil, MakeGitError(ret)
+	}
+
+	return oid, nil
+}
+
 // CreateCommitBuffer creates a commit and write it into a buffer.
 func (v *Repository) CreateCommitBuffer(
 	author, committer *Signature,