Add overwrites (#109)

Relates to kairos-io/kairos#2492

Signed-off-by: Mauro Morales <mauro.morales@spectrocloud.com>

collector/collector.go

@@ -235,7 +235,16 @@ func Scan(o *Options, filter func(d []byte) ([]byte, error)) (*Config, error) {
 		}
 	}
 
-	return configs.Merge()
+	mergedConfig, err := configs.Merge()
+	if err != nil {
+		return mergedConfig, err
+	}
+
+	if o.Overwrites != "" {
+		yaml.Unmarshal([]byte(o.Overwrites), &mergedConfig) //nolint:errcheck
+	}
+
+	return mergedConfig, nil
 }
 
 func allFiles(dir []string) []string {

collector/collector_test.go

@@ -661,6 +661,83 @@ stages:
 			})
 		})
 
+		Context("With Overwrittes", func() {
+			var tmpDir1 string
+			var err error
+
+			BeforeEach(func() {
+				tmpDir1, err = os.MkdirTemp("", "config1")
+				Expect(err).ToNot(HaveOccurred())
+				err := os.WriteFile(path.Join(tmpDir1, "local_config_1.yaml"), []byte(`#cloud-config
+install:
+  auto: false
+foo: bar
+stages:
+  initramfs:
+    - users:
+        kairos:
+          groups:
+            - sudo
+          passwd: kairos
+`), os.ModePerm)
+				Expect(err).ToNot(HaveOccurred())
+			})
+
+			AfterEach(func() {
+				err = os.RemoveAll(tmpDir1)
+				Expect(err).ToNot(HaveOccurred())
+			})
+
+			It("replaces completely the keys given by the overwrite", func() {
+				o := &Options{}
+				overwriteYaml := `#cloud-config
+install:
+  auto: true
+options:
+  device: /dev/sda
+stages:
+  initramfs:
+    - users:
+        kairos:
+          groups:
+            - sudo
+          passwd: kairos
+        foobar:
+          groups:
+            - sudo
+          passwd: barbaz
+`
+				err = o.Apply(
+					Directories(tmpDir1),
+					Overwrites(overwriteYaml),
+				)
+				Expect(err).ToNot(HaveOccurred())
+
+				c, err := Scan(o, FilterKeysTestMerge)
+				Expect(err).ToNot(HaveOccurred())
+
+				Expect(c.String()).To(Equal(`#cloud-config
+
+foo: bar
+install:
+    auto: true
+options:
+    device: /dev/sda
+stages:
+    initramfs:
+        - users:
+            foobar:
+                groups:
+                    - sudo
+                passwd: barbaz
+            kairos:
+                groups:
+                    - sudo
+                passwd: kairos
+`))
+			})
+		})
+
 		Context("Deep merge maps within arrays", func() {
 			var cmdLinePath, tmpDir1 string
 			var err error

collector/options.go

@@ -12,6 +12,7 @@ type Options struct {
 	NoLogs           bool
 	StrictValidation bool
 	Readers          []io.Reader
+	Overwrites       string
 }
 
 type Option func(o *Options) error
@@ -72,3 +73,10 @@ func Readers(r ...io.Reader) Option {
 		return nil
 	}
 }
+
+func Overwrites(m string) Option {
+	return func(o *Options) error {
+		o.Overwrites = m
+		return nil
+	}
+}