Confine cleanup and use held session locks

internal/artifacts/lock_common.go

@@ -0,0 +1,18 @@
+package artifacts
+
+import (
+	"errors"
+	"os"
+)
+
+var errHeldLockConflict = errors.New("held lock conflict")
+
+var acquireHeldFileLockFn = acquireHeldFileLock
+var releaseHeldFileLockFn = releaseHeldFileLock
+
+func closeHeldLockFile(file *os.File) error {
+	if file == nil {
+		return nil
+	}
+	return file.Close()
+}