feat: parse all Go CLIs with flaggy; dump bash complete. (#36)

stdlib flag dropped --hop after the query. One wrapper in internal/cli,
source <(./bin/cli/complete.go bash). Gitea #34.

internal/ocr/args.go

@@ -0,0 +1,35 @@
+package ocr
+
+import (
+	"fmt"
+
+	"github.com/eSlider/2dph/internal/cli"
+	"github.com/integrii/flaggy"
+)
+
+type CLI struct {
+	Path string
+}
+
+func Parser() *flaggy.Parser {
+	c := CLI{}
+	return Bind(&c)
+}
+
+func Bind(c *CLI) *flaggy.Parser {
+	p := cli.New("mail-ocr")
+	p.Description = "tesseract eng+deu on image or scanned PDF"
+	p.AddPositionalValue(&c.Path, "file", 1, false, "image or pdf")
+	return p
+}
+
+func ParseArgs(args []string) (CLI, error) {
+	var c CLI
+	if err := cli.Parse(Bind(&c), args); err != nil {
+		return c, err
+	}
+	if c.Path == "" {
+		return c, fmt.Errorf("usage: bin/mail/ocr.go <image|pdf>")
+	}
+	return c, nil
+}