fix: allow actions artifacts storage migration to complete succesfully (#31251)

Change the copy to use `ActionsArtifact.StoragePath` instead of the
`ArtifactPath`. Skip artifacts that are expired, and don't error if the
file to copy does not exist.

---

When trying to migrate actions artifact storage from local to MinIO, we
encountered errors that prevented the process from completing
successfully:

* The migration tries to copy the files using the per-run
`ArtifactPath`, instead of the unique `StoragePath`.
* Artifacts that have been marked expired and had their files deleted
would throw an error
* Artifacts that are pending, but don't have a file uploaded yet will
throw an error.

This PR addresses these cases, and allow the process to complete
successfully.

cmd/migrate_storage.go

@@ -5,7 +5,9 @@ package cmd
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"io/fs"
 	"strings"
 
 	actions_model "code.gitea.io/gitea/models/actions"
@@ -194,8 +196,20 @@ func migrateActionsLog(ctx context.Context, dstStorage storage.ObjectStorage) er
 
 func migrateActionsArtifacts(ctx context.Context, dstStorage storage.ObjectStorage) error {
 	return db.Iterate(ctx, nil, func(ctx context.Context, artifact *actions_model.ActionArtifact) error {
-		_, err := storage.Copy(dstStorage, artifact.ArtifactPath, storage.ActionsArtifacts, artifact.ArtifactPath)
+		if artifact.Status == int64(actions_model.ArtifactStatusExpired) {
-		return err
+			return nil
+		}
+
+		_, err := storage.Copy(dstStorage, artifact.StoragePath, storage.ActionsArtifacts, artifact.StoragePath)
+		if err != nil {
+			// ignore files that do not exist
+			if errors.Is(err, fs.ErrNotExist) {
+				return nil
+			}
+			return err
+		}
+
+		return nil
 	})
 }