[maint] exit code added in error type (#1006)

git/command/command.go

@@ -133,13 +133,15 @@ func (c *Command) Run(ctx context.Context, opts ...RunOptionFunc) (err error) {
 
 		return ctx.Err()
 	case err = <-result:
-		if err != nil && errAsBuff {
+		if err == nil {
-			buff, ok := options.Stderr.(*bytes.Buffer)
+			return nil
-			if ok {
-				return NewError(err, buff.Bytes())
-			}
 		}
-		return err
+
+		var stderr []byte
+		if buff, ok := options.Stderr.(*bytes.Buffer); ok && errAsBuff {
+			stderr = buff.Bytes()
+		}
+		return NewError(err, stderr)
 	}
 }
 

git/command/error.go

@@ -17,6 +17,7 @@ package command
 import (
 	"errors"
 	"fmt"
+	"os/exec"
 )
 
 var (
@@ -24,7 +25,7 @@ var (
 	ErrInvalidArg = errors.New("invalid argument")
 )
 
-// Error type with optional Stderr payload.
+// Error type with optional ExitCode and Stderr payload.
 type Error struct {
 	Err    error
 	StdErr []byte
@@ -38,6 +39,15 @@ func NewError(err error, stderr []byte) *Error {
 	}
 }
 
+func (e *Error) ExitCode() int {
+	var exitErr *exec.ExitError
+	ok := errors.As(e.Err, &exitErr)
+	if ok {
+		return exitErr.ExitCode()
+	}
+	return 0
+}
+
 func (e *Error) Error() string {
 	if len(e.StdErr) != 0 {
 		return fmt.Sprintf("%s: %s", e.Err.Error(), e.StdErr)
@@ -45,6 +55,10 @@ func (e *Error) Error() string {
 	return e.Err.Error()
 }
 
+func (e *Error) Unwrap() error {
+	return e.Err
+}
+
 // AsError unwraps Error otherwise return nil.
 func AsError(err error) (e *Error) {
 	if errors.As(err, &e) {