Add gpg key path and passphrase as args

Signed-off-by: Somtochi Onyekwere <somtochionyekwere@gmail.com>

internal/bootstrap/git/gogit/gogit.go

@@ -25,6 +25,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/ProtonMail/go-crypto/openpgp"
 	gogit "github.com/go-git/go-git/v5"
 	"github.com/go-git/go-git/v5/config"
 	"github.com/go-git/go-git/v5/plumbing"
@@ -40,6 +41,12 @@ type GoGit struct {
 	repository *gogit.Repository
 }
 
+type CommitOptions struct {
+	GpgKeyPath       string
+	GpgKeyPassphrase string
+	KeyID            string
+}
+
 func New(path string, auth transport.AuthMethod) *GoGit {
 	return &GoGit{
 		path: path,
@@ -127,7 +134,7 @@ func (g *GoGit) Write(path string, reader io.Reader) error {
 	return err
 }
 
-func (g *GoGit) Commit(message git.Commit) (string, error) {
+func (g *GoGit) Commit(message git.Commit, opts ...git.Option) (string, error) {
 	if g.repository == nil {
 		return "", git.ErrNoGitRepository
 	}
@@ -142,6 +149,12 @@ func (g *GoGit) Commit(message git.Commit) (string, error) {
 		return "", err
 	}
 
+	// apply the options
+	options := &git.CommitOptions{}
+	for _, opt := range opts {
+		opt.ApplyToCommit(options)
+	}
+
 	// go-git has [a bug](https://github.com/go-git/go-git/issues/253)
 	// whereby it thinks broken symlinks to absolute paths are
 	// modified. There's no circumstance in which we want to commit a
@@ -173,13 +186,24 @@ func (g *GoGit) Commit(message git.Commit) (string, error) {
 		return head.Hash().String(), git.ErrNoStagedFiles
 	}
 
-	commit, err := wt.Commit(message.Message, &gogit.CommitOptions{
+	commitOpts := &gogit.CommitOptions{
 		Author: &object.Signature{
 			Name:  message.Name,
 			Email: message.Email,
 			When:  time.Now(),
 		},
-	})
+	}
+
+	if options.GPGSigningInfo != nil {
+		entity, err := getOpenPgpEntity(*options.GPGSigningInfo)
+		if err != nil {
+			return "", err
+		}
+
+		commitOpts.SignKey = entity
+	}
+
+	commit, err := wt.Commit(message.Message, commitOpts)
 	if err != nil {
 		return "", err
 	}
@@ -232,3 +256,41 @@ func (g *GoGit) Path() string {
 func isRemoteBranchNotFoundErr(err error, ref string) bool {
 	return strings.Contains(err.Error(), fmt.Sprintf("couldn't find remote ref %q", ref))
 }
+
+func getOpenPgpEntity(info git.GPGSigningInfo) (*openpgp.Entity, error) {
+	r, err := os.Open(info.PrivateKeyPath)
+	if err != nil {
+		return nil, err
+	}
+
+	entityList, err := openpgp.ReadKeyRing(r)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(entityList) == 0 {
+		return nil, fmt.Errorf("no entity formed")
+	}
+
+	var entity *openpgp.Entity
+	if info.KeyID != "" {
+		for _, ent := range entityList {
+			if ent.PrimaryKey.KeyIdString() == info.KeyID {
+				entity = ent
+			}
+		}
+
+		if entity == nil {
+			return nil, fmt.Errorf("no key matching the key id was found")
+		}
+	} else {
+		entity = entityList[0]
+	}
+
+	err = entity.PrivateKey.Decrypt([]byte(info.Passphrase))
+	if err != nil {
+		return nil, err
+	}
+
+	return entity, nil
+}

internal/bootstrap/git/gogit/gogit_test.go

@@ -0,0 +1,66 @@
+// +build unit
+
+package gogit
+
+import (
+	"testing"
+
+	"github.com/fluxcd/flux2/internal/bootstrap/git"
+)
+
+func TestGetOpenPgpEntity(t *testing.T) {
+	tests := []struct {
+		name       string
+		keyPath    string
+		passphrase string
+		id         string
+		expectErr  bool
+	}{
+		{
+			name:       "no default key id given",
+			keyPath:    "testdata/private.key",
+			passphrase: "flux",
+			id:         "",
+			expectErr:  false,
+		},
+		{
+			name:       "key id given",
+			keyPath:    "testdata/private.key",
+			passphrase: "flux",
+			id:         "0619327DBD777415",
+			expectErr:  false,
+		},
+		{
+			name:       "wrong key id",
+			keyPath:    "testdata/private.key",
+			passphrase: "flux",
+			id:         "0619327DBD777416",
+			expectErr:  true,
+		},
+		{
+			name:       "wrong password",
+			keyPath:    "testdata/private.key",
+			passphrase: "fluxe",
+			id:         "0619327DBD777415",
+			expectErr:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gpgInfo := git.GPGSigningInfo{
+				PrivateKeyPath: tt.keyPath,
+				Passphrase:     tt.passphrase,
+				KeyID:          tt.id,
+			}
+
+			_, err := getOpenPgpEntity(gpgInfo)
+			if err != nil && !tt.expectErr {
+				t.Errorf("unexpected error: %s", err)
+			}
+			if err == nil && tt.expectErr {
+				t.Errorf("expected error when %s", tt.name)
+			}
+		})
+	}
+}