Initial release: Go Jdenticon library v0.1.0

- Core library with SVG and PNG generation
- CLI tool with generate and batch commands
- Cross-platform path handling for Windows compatibility
- Comprehensive test suite with integration tests

cmd/jdenticon/types.go

@@ -0,0 +1,35 @@
+package main
+
+import "fmt"
+
+// FormatFlag is a custom pflag.Value for handling --format validation and completion
+type FormatFlag string
+
+const (
+	// FormatPNG represents PNG output format for identicon generation
+	FormatPNG FormatFlag = "png"
+
+	// FormatSVG represents SVG output format for identicon generation
+	FormatSVG FormatFlag = "svg"
+)
+
+// String is used both by pflag and fmt.Stringer
+func (f *FormatFlag) String() string {
+	return string(*f)
+}
+
+// Set must have pointer receiver, so it can change the value of f.
+func (f *FormatFlag) Set(v string) error {
+	switch v {
+	case "png", "svg":
+		*f = FormatFlag(v)
+		return nil
+	default:
+		return fmt.Errorf(`must be one of "png" or "svg"`)
+	}
+}
+
+// Type is only used in help text
+func (f *FormatFlag) Type() string {
+	return "string"
+}