Fix block style strip multi-line issue

As reported in homeport/dyff#180, when using text
that spans over multiple lines using the strip option (`|-`), the output was
not created correctly.

Simplify multi-line output code to properly place a newline at every line with
the last line being an exception.

output_yaml.go

@@ -292,13 +292,12 @@ func (p *OutputProcessor) neatYAMLofNode(prefix string, skipIndentOnFirstLine bo
 			colorName = "multiLineTextColor"
 			fmt.Fprint(p.out, p.colorize("|", colorName), "\n")
 			for i, line := range lines {
-				if i == len(lines)-1 {
-					continue
-				}
-
-				fmt.Fprint(p.out, prefix, p.colorize(line, colorName))
+				fmt.Fprint(p.out,
+					prefix,
+					p.colorize(line, colorName),
+				)
 
-				if i < len(lines)-2 {
+				if i != len(lines)-1 {
 					fmt.Fprint(p.out, "\n")
 				}
 			}

output_yaml_test.go

@@ -194,7 +194,7 @@ list: # at list definition
 - two # two
 
 # before multiline
-multiline: |
+multiline: |-
   This is
   a multi
   line te
@@ -333,6 +333,37 @@ yaml:
 			Expect(err).ToNot(HaveOccurred())
 			Expect(output).To(BeEquivalentTo(expected))
 		})
+
+		It("should create YAML output of multi-line text", func() {
+			example := []byte(`---
+data:
+  repos.yaml: |-
+    repos:
+    - apply_requirements:
+      - approved
+      - mergeable
+      id: /.*/
+      test: /.*/
+`)
+
+			expected := `---
+data:
+  repos.yaml: |
+    repos:
+    - apply_requirements:
+      - approved
+      - mergeable
+      id: /.*/
+      test: /.*/
+`
+
+			var node yamlv3.Node
+			Expect(yamlv3.Unmarshal(example, &node)).ToNot(HaveOccurred())
+
+			output, err := ToYAMLString(node)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(output).To(BeEquivalentTo(expected))
+		})
 	})
 
 	Context("create YAML output for type struct", func() {