suite init и suite add: заведение набора и конвенции в двух режимах

- suite init создаёт директорию и манифест со скелетом таблиц; suite add пишет
  файл конвенции и вправляет запись в suite.toml, сохраняя комментарии
- без аргументов команды спрашивают поля с подсказками, с флагами берут всё
  сразу и не спрашивают ничего; без терминала пустой вызов отказывает
- строка о версии языка генерируется из словаря набора, поэтому созданный файл
  проходит suite check без правок
- починено разрешение extends: короткая форма бралась по суффиксу и могла
  указать на сам файл; теперь неоднозначность либо избегается при записи, либо
  сообщается ошибкой

internal/cli/prompt.go

@@ -0,0 +1,122 @@
+package cli
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+)
+
+// Commands that change something run in two modes, and which one is meant is
+// read off the command line: bare means interactive, any flag means automatic.
+//
+// The two modes address two different callers. A person types the command and
+// is walked through the fields with a hint for each; an agent or a script
+// passes every field at once and must never be blocked waiting on a terminal
+// that is not there. Neither mode guesses: a field that is required and absent
+// stops the run in both.
+
+// Field is one thing a command asks for.
+type Field struct {
+	// Flag is the name the field carries on the command line.
+	Flag string
+	// Ask is the question put to a person.
+	Ask string
+	// Hint is the one line explaining what belongs here and why.
+	Hint string
+	// Default is offered as the answer when the person just presses enter.
+	Default string
+	// Optional fields may stay empty.
+	Optional bool
+	// Check validates an answer; it is applied in both modes.
+	Check func(string) error
+}
+
+// errStop ends the dialogue on end of input.
+var errStop = errors.New("input ended")
+
+// dialogue asks the fields one by one, re-asking what did not pass validation.
+type dialogue struct {
+	in  *bufio.Reader
+	out io.Writer
+}
+
+func newDialogue(env Env) *dialogue {
+	return &dialogue{in: bufio.NewReader(env.In), out: env.Out}
+}
+
+// ask puts one question and returns the answer, looping until it validates.
+func (d *dialogue) ask(f Field) (string, error) {
+	for {
+		if f.Hint != "" {
+			fmt.Fprintf(d.out, "\n%s\n", f.Hint)
+		}
+		prompt := f.Ask
+		switch {
+		case f.Default != "":
+			prompt += fmt.Sprintf(" [%s]", f.Default)
+		case f.Optional:
+			prompt += " [may stay empty]"
+		}
+		fmt.Fprintf(d.out, "%s: ", prompt)
+
+		line, err := d.in.ReadString('\n')
+		answer := strings.TrimSpace(line)
+		if answer == "" && err != nil {
+			return "", errStop
+		}
+		if answer == "" {
+			answer = f.Default
+		}
+		if answer == "" && !f.Optional {
+			fmt.Fprintln(d.out, "  the field is required")
+			continue
+		}
+		if err := validate(f, answer); err != nil {
+			fmt.Fprintf(d.out, "  %s\n", err)
+			continue
+		}
+		return answer, nil
+	}
+}
+
+// validate applies a field's check to a value that is not empty.
+func validate(f Field, value string) error {
+	if value == "" || f.Check == nil {
+		return nil
+	}
+	return f.Check(value)
+}
+
+// resolve settles the fields in automatic mode: what came on the command line
+// is validated, what is required and missing is named. Every missing field is
+// reported at once — being sent back one flag at a time is the worst way to
+// learn what a command wants.
+func resolve(fields []Field, given map[string]string) error {
+	var missing []string
+	var problems []string
+	for _, f := range fields {
+		value := given[f.Flag]
+		if value == "" {
+			value = f.Default
+			given[f.Flag] = value
+		}
+		if value == "" {
+			if !f.Optional {
+				missing = append(missing, "--"+f.Flag)
+			}
+			continue
+		}
+		if err := validate(f, value); err != nil {
+			problems = append(problems, fmt.Sprintf("--%s: %s", f.Flag, err))
+		}
+	}
+	if len(missing) > 0 {
+		problems = append(problems, "required and missing: "+strings.Join(missing, ", "))
+	}
+	if len(problems) > 0 {
+		return errors.New(strings.Join(problems, "\n"))
+	}
+	return nil
+}