feat: implement init

Signed-off-by: Brian McGee <brian@bmcgee.ie>

cli/cli.go

@@ -20,6 +20,7 @@ type Format struct {
 	Walk                  walk.Type          `enum:"auto,git,filesystem" default:"auto" help:"The method used to traverse the files within --tree-root. Currently supports 'auto', 'git' or 'filesystem'."`
 	Verbosity             int                `name:"verbose" short:"v" type:"counter" default:"0" env:"LOG_LEVEL" help:"Set the verbosity of logs e.g. -vv."`
 	Version               bool               `name:"version" short:"V" help:"Print version"`
+	Init                  bool               `name:"init" short:"i" help:"Create a new treefmt.toml"`
 
 	Paths []string `name:"paths" arg:"" type:"path" optional:"" help:"Paths to format. Defaults to formatting the whole tree."`
 	Stdin bool     `help:"Format the context passed in via stdin"`

init.toml

@@ -0,0 +1,11 @@
+# One CLI to format the code tree - https://git.numtide.com/numtide/treefmt
+
+[formatter.mylanguage]
+# Formatter to run
+command = "command-to-run"
+# Command-line arguments for the command
+options = []
+# Glob pattern of files to include
+includes = [ "*.<language-extension>" ]
+# Glob patterns of files to exclude
+excludes = []

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	_ "embed"
 	"fmt"
 	"os"
 
@@ -9,6 +10,11 @@ import (
 	"github.com/alecthomas/kong"
 )
 
+// We embed the sample toml file for use with the init flag.
+//
+//go:embed init.toml
+var initBytes []byte
+
 func main() {
 	// This is to maintain compatibility with 1.0.0 which allows specifying the version with a `treefmt --version` flag
 	// on the 'default' command. With Kong it would be better to have `treefmt version` so it would be treated as a
@@ -18,6 +24,14 @@ func main() {
 		if arg == "--version" || arg == "-V" {
 			fmt.Printf("%s %s\n", build.Name, build.Version)
 			return
+		} else if arg == "--init" || arg == "-i" {
+			if err := os.WriteFile("treefmt.toml", initBytes, 0o644); err != nil {
+				fmt.Printf("Failed to write treefmt.toml: %v\n", err)
+				os.Exit(1)
+			}
+
+			fmt.Printf("Generated treefmt.toml. Now it's your turn to edit it.\n")
+			return
 		}
 	}