fix(server): fix error handling when ancestor commit not found

server/path_publish.go

@@ -2,6 +2,7 @@ package server
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 
@@ -138,6 +139,16 @@ func (b *Backend) pathPublish(ctx context.Context, req *logical.Request, fields
 
 			isAncestor, err := trdlGit.IsAncestor(gitRepo, lastPublishedGitCommit, headRef.Hash().String())
 			if err != nil {
+				var ancestorErr *trdlGit.AncestorCommitLookupError
+				if errors.As(err, &ancestorErr) {
+					msg := fmt.Sprintf(
+						"Previously published commit %q not found in the Git repository: %v. This might have been caused by a force push rewriting history. If you're confident this is expected, you can override 'last_published_git_commit' option in the project configuration.",
+						lastPublishedGitCommit, ancestorErr,
+					)
+					logboek.Context(ctx).Default().LogF(msg)
+					b.Logger().Error(msg)
+					return err
+				}
 				return err
 			}
 

server/pkg/git/repository.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"strings"
 	"time"
 
 	"github.com/go-git/go-billy/v5/memfs"
@@ -169,15 +170,34 @@ func ReadWorktreeFile(gitRepo *git.Repository, path string) ([]byte, error) {
 	return data, nil
 }
 
+type AncestorCommitLookupError struct {
+	Commit string
+	Err    error
+}
+
+func (e *AncestorCommitLookupError) Error() string {
+	return fmt.Sprintf("unable to get ancestor commit %q object: %v", e.Commit, e.Err)
+}
+
+func (e *AncestorCommitLookupError) Unwrap() error {
+	return e.Err
+}
+
 func IsAncestor(gitRepo *git.Repository, ancestorCommit, descendantCommit string) (bool, error) {
 	ancestorCommitObj, err := gitRepo.CommitObject(plumbing.NewHash(ancestorCommit))
 	if err != nil {
-		return false, fmt.Errorf("unable to get commit %q object: %w", ancestorCommit, err)
+		if strings.Contains(err.Error(), "object not found") {
+			return false, &AncestorCommitLookupError{
+				Commit: ancestorCommit,
+				Err:    err,
+			}
+		}
+		return false, fmt.Errorf("unable to get ancestor commit %q object: %w", ancestorCommit, err)
 	}
 
 	descendantCommitObj, err := gitRepo.CommitObject(plumbing.NewHash(descendantCommit))
 	if err != nil {
-		return false, fmt.Errorf("unable to get commit %q object: %w", descendantCommitObj, err)
+		return false, fmt.Errorf("unable to get descendant commit %q object: %w", descendantCommitObj, err)
 	}
 
 	isAncestor, err := ancestorCommitObj.IsAncestor(descendantCommitObj)