Start work on getting rid of the cobra dependency

Command line parsing is easy and I can do it better.

tools/cli/option-from-string.go

@@ -0,0 +1,142 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package cli
+
+import (
+	"bufio"
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var _ = fmt.Print
+
+// OptionFromString {{{
+
+/*
+Create an [Option] from a string. Syntax is::
+
+	--option-name, --option-alias, -s
+	type: string
+	dest: destination
+	choices: choice1, choice2, choice 3
+	depth: 0
+	Help text on multiple lines. Indented lines are peserved as indented blocks. Blank lines
+	are preserved as blank lines. #placeholder_for_formatting# is replaced by the empty string.
+
+Available types are: string, str, list, int, float, count, bool-set, bool-reset, choices
+The default dest is the first --option-name which must be a long option.
+If choices are specified type is set to choices automatically.
+If depth is negative option is added to all subcommands. If depth is positive option is added to sub-commands upto
+the specified depth.
+Set the help text to "!" to have an option hidden.
+*/
+func OptionFromString(entries ...string) (*Option, error) {
+	if mpat == nil {
+		mpat = regexp.MustCompile("^([a-z]+)=(.+)")
+	}
+	ans := Option{}
+	scanner := bufio.NewScanner(strings.NewReader(strings.Join(entries, "\n")))
+	in_help := false
+	prev_indent := 0
+	help := strings.Builder{}
+	help.Grow(2048)
+
+	indent_of_line := func(x string) int {
+		return len(x) - len(strings.TrimLeft(x, " \n\t\v\f"))
+	}
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if ans.Aliases == nil {
+			if strings.HasPrefix(line, "--") {
+				parts := strings.Split(line, " ")
+				ans.Name = strings.ReplaceAll(parts[0], "-", "_")
+				ans.Aliases = make([]Alias, 0, len(parts))
+				for i, x := range parts {
+					ans.Aliases[i] = Alias{NameWithoutHyphens: strings.TrimLeft(x, "-"), IsShort: !strings.HasPrefix(x, "--")}
+				}
+			}
+		} else if in_help {
+			if line != "" {
+				current_indent := indent_of_line(line)
+				if current_indent > 1 {
+					if prev_indent == 0 {
+						help.WriteString("\n")
+					} else {
+						line = strings.TrimSpace(line)
+					}
+				}
+				prev_indent = current_indent
+				if !strings.HasSuffix(help.String(), "\n") {
+					help.WriteString(" ")
+				}
+				help.WriteString(line)
+			} else {
+				prev_indent = 0
+				help.WriteString("\n")
+				if !strings.HasSuffix(help.String(), "::") {
+					help.WriteString("\n")
+				}
+			}
+		} else {
+			matches := mpat.FindStringSubmatch(line)
+			if matches == nil {
+				continue
+			}
+			k, v := matches[1], matches[2]
+			switch k {
+			case "choices":
+				parts := strings.Split(v, ",")
+				ans.Choices = make(map[string]bool, len(parts))
+				ans.OptionType = StringOption
+				for i, x := range parts {
+					x = strings.TrimSpace(x)
+					ans.Choices[x] = true
+					if i == 0 && ans.Default == "" {
+						ans.Default = x
+					}
+				}
+			case "default":
+				ans.Default = v
+			case "dest":
+				ans.Name = v
+			case "depth":
+				depth, err := strconv.ParseInt(v, 0, 0)
+				if err != nil {
+					return nil, err
+				}
+				ans.Depth = int(depth)
+			case "condition", "completion":
+			default:
+				return nil, fmt.Errorf("Unknown option metadata key: %s", k)
+			case "type":
+				switch v {
+				case "choice", "choices":
+					ans.OptionType = StringOption
+				case "int":
+					ans.OptionType = IntegerOption
+				case "float":
+					ans.OptionType = FloatOption
+				case "count":
+					ans.OptionType = CountOption
+				case "bool-set":
+					ans.OptionType = BoolOption
+				case "bool-reset":
+					ans.OptionType = BoolOption
+					for _, a := range ans.Aliases {
+						a.IsUnset = true
+					}
+				case "list", "str", "string":
+					ans.OptionType = StringOption
+				default:
+					return nil, fmt.Errorf("Unknown option type: %s", v)
+				}
+			}
+		}
+	}
+	ans.HelpText = help.String()
+	ans.Hidden = ans.HelpText == "!"
+	return &ans, nil
+} // }}}