cmd: force no color output when NO_COLOR env presents

cmd/constant.go

@@ -1,5 +1,7 @@
 package cmd
 
+import "os"
+
 var unwrapScalarFlag = newUnwrapFlag()
 
 var unwrapScalar = false
@@ -12,9 +14,6 @@ var outputFormat = ""
 var inputFormat = ""
 
 var exitStatus = false
-var forceColor = false
-var forceNoColor = false
-var colorsEnabled = false
 var indent = 2
 var noDocSeparators = false
 var nullInput = false
@@ -23,6 +22,16 @@ var verbose = false
 var version = false
 var prettyPrint = false
 
+var forceColor = false
+var forceNoColor = false
+var colorsEnabled = false
+
+func init() {
+	// when NO_COLOR environment variable presents and not an empty string the colored output should be disabled;
+	// refer to no-color.org
+	forceNoColor = os.Getenv("NO_COLOR") != ""
+}
+
 // can be either "" (off), "extract" or "process"
 var frontMatter = ""