gitaly-git2go: Extract CommitNotFoundError

We are looking to expose the fact that a commit was not found at the RPC
level. In order to do this we need to distinguish the error in git2go by
creating a new error type over gob.

4 files changed, 23 insertions, 5 deletions

diff --git a/cmd/gitaly-git2go/cherry_pick_test.go b/cmd/gitaly-git2go/cherry_pick_test.go
index 82f11cd11..93308da28 100644
--- a/cmd/gitaly-git2go/cherry_pick_test.go
+++ b/cmd/gitaly-git2go/cherry_pick_test.go
@@ -133,14 +133,16 @@ func TestCherryPick(t *testing.T) {
 		},
 		{
 			desc:           "fails on nonexistent ours commit",
-			expectedErrMsg: "cherry-pick: ours commit lookup: lookup commit \"nonexistent\": revspec 'nonexistent' not found",
+			expectedErrAs:  &git2go.CommitNotFoundError{},
+			expectedErrMsg: "cherry-pick: ours commit lookup: commit not found: \"nonexistent\"",
 		},
 		{
 			desc: "fails on nonexistent cherry-pick commit",
 			ours: []gittest.TreeEntry{
 				{Path: "file", Content: "fooqux", Mode: "100644"},
 			},
-			expectedErrMsg: "cherry-pick: commit lookup: lookup commit \"nonexistent\": revspec 'nonexistent' not found",
+			expectedErrAs:  &git2go.CommitNotFoundError{},
+			expectedErrMsg: "cherry-pick: commit lookup: commit not found: \"nonexistent\"",
 		},
 	}
 	for _, tc := range testcases {
diff --git a/cmd/gitaly-git2go/revert_test.go b/cmd/gitaly-git2go/revert_test.go
index 0c96988ee..b4f3fbe8c 100644
--- a/cmd/gitaly-git2go/revert_test.go
+++ b/cmd/gitaly-git2go/revert_test.go
@@ -155,7 +155,7 @@ func TestRevert_trees(t *testing.T) {
 
 				return "nonexistent", revertOid.String()
 			},
-			expectedErr: "revert: ours commit lookup: lookup commit \"nonexistent\": revspec 'nonexistent' not found",
+			expectedErr: "revert: ours commit lookup: commit not found: \"nonexistent\"",
 		},
 		{
 			desc: "nonexistent revert fails",
@@ -166,7 +166,7 @@ func TestRevert_trees(t *testing.T) {
 
 				return oursOid.String(), "nonexistent"
 			},
-			expectedErr: "revert: revert commit lookup: lookup commit \"nonexistent\": revspec 'nonexistent' not found",
+			expectedErr: "revert: revert commit lookup: commit not found: \"nonexistent\"",
 		},
 	}
 	for _, tc := range testcases {
diff --git a/cmd/gitaly-git2go/util.go b/cmd/gitaly-git2go/util.go
index a6ecd2a33..187ce0708 100644
--- a/cmd/gitaly-git2go/util.go
+++ b/cmd/gitaly-git2go/util.go
@@ -6,11 +6,15 @@ import (
 	"fmt"
 
 	git "github.com/libgit2/git2go/v34"
+	"gitlab.com/gitlab-org/gitaly/v15/internal/git2go"
 )
 
 func lookupCommit(repo *git.Repository, ref string) (*git.Commit, error) {
 	object, err := repo.RevparseSingle(ref)
-	if err != nil {
+	switch {
+	case git.IsErrorCode(err, git.ErrorCodeNotFound):
+		return nil, git2go.CommitNotFoundError{Revision: ref}
+	case err != nil:
 		return nil, fmt.Errorf("lookup commit %q: %w", ref, err)
 	}
 
diff --git a/internal/git2go/serialization.go b/internal/git2go/serialization.go
index b4967ca25..0f4949c5f 100644
--- a/internal/git2go/serialization.go
+++ b/internal/git2go/serialization.go
@@ -3,6 +3,7 @@ package git2go
 import (
 	"encoding/gob"
 	"errors"
+	"fmt"
 	"reflect"
 )
 
@@ -29,6 +30,7 @@ var registeredTypes = map[reflect.Type]struct{}{
 	reflect.TypeOf(EmptyError{}):             {},
 	reflect.TypeOf(IndexError("")):           {},
 	reflect.TypeOf(ConflictError{}):          {},
+	reflect.TypeOf(CommitNotFoundError{}):    {},
 }
 
 // Result is the serialized result.
@@ -78,6 +80,16 @@ func (err EmptyError) Error() string {
 	return "could not apply because the result was empty"
 }
 
+// CommitNotFoundError indicates that the given commit rev could not be found.
+type CommitNotFoundError struct {
+	// Revision used to lookup the commit
+	Revision string
+}
+
+func (err CommitNotFoundError) Error() string {
+	return fmt.Sprintf("commit not found: %q", err.Revision)
+}
+
 // SerializableError returns an error that is Gob serializable.
 // Registered types are serialized directly. Unregistered types
 // are transformed in to an opaque error using their error message.