[TOML ConfigSource] add support for executing fallback CLI commands

Signed-off-by: Tariq Ibrahim <tibrahim@nvidia.com>
Co-authored-by: Evan Lezar <elezar@nvidia.com>

pkg/config/toml/list.go

@@ -0,0 +1,41 @@
+/**
+# Copyright 2024 NVIDIA CORPORATION
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package toml
+
+import "errors"
+
+type firstOf []Loader
+
+func LoadFirst(loaders ...Loader) Loader {
+	return firstOf(loaders)
+}
+
+func (loaders firstOf) Load() (*Tree, error) {
+	var errs error
+	for _, loader := range loaders {
+		if loader == nil {
+			continue
+		}
+		tree, err := loader.Load()
+		if err != nil {
+			errs = errors.Join(errs, err)
+			continue
+		}
+		return tree, nil
+	}
+	return nil, errs
+}