gitnore.go

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"os"
	osuser "os/user"
	"strings"
)

var (
	src, dest *string
	user      *osuser.User
)

var mapping map[string]string

func init() {
	src = flag.String("i", "", "Source File")
	dest = flag.String("o", ".gitignore", "Destination File")
}

func main() {
	flag.Parse()
	flag.Usage = usage

	if len(os.Args) == 1 {
		usage()
		os.Exit(1)
	}

	var err error
	user, err = osuser.Current()
	if err != nil {
		fmt.Printf("Error when checking current user: %s\n", err.Error())
		os.Exit(1)
	}

	// setup source dir
	sourceDir = fmt.Sprintf("%s/.gitnore", user.HomeDir)

	cmd := os.Args[1]

	if cmd == "update" {
		updateMap()
	}

	mapping = listMap()
	if cmd == "list" {
		printMap(mapping)
		os.Exit(0)
	}

	configs := strings.Split(*src, ",")
	for index, config := range configs {
		if config == "" {
			fmt.Println("A specified src parameter was found to be empty")
			usage()
		}

		var (
			b, existing []byte
			ok          bool
			path        string
		)

		if path, ok = mapping[config]; !ok {
			fmt.Printf("unknown source file of: %s\n", config)
			os.Exit(1)
		}

		if b, err = ioutil.ReadFile(path); err != nil {
			fmt.Println(err.Error())
			os.Exit(1)
		}
		// If not first iteration, read destination for appending multiple configurations
		if index != 0 {
			if existing, err = ioutil.ReadFile(*dest); err != nil {
				fmt.Println(err.Error())
				os.Exit(1)
			}
			b = append(append(existing, []byte("\n")...), b...)
		}
		if err = ioutil.WriteFile(*dest, b, 0644); err != nil {
			fmt.Println(err.Error())
			os.Exit(1)
		}
		fmt.Printf("Writing %s into %s.\n", path, *dest)
	}
}

func usage() {
	fmt.Println("Usage: ./gitnore -i language -o .gitignore")
	fmt.Println()
	fmt.Println("Available commands:")
	fmt.Println("\tupdate \t: Update gitignore dictionary")
	fmt.Println("\tlist \t: List available gitignore")
	fmt.Println()
	fmt.Println("Parameters:")
	fmt.Println("\t-i \t: Select Language (-i python or -i java,go)")
	fmt.Println("\t-o \t: Output filename (default .gitignore)")
	fmt.Println()
	fmt.Println("Example usage:")
	fmt.Println("\t$ gitnore -i python \t\t: default set to .gitignore")
	fmt.Println("\t$ gitnore -i java,go \t\t: with multiple languages")
	fmt.Println("\t$ gitnore -i go -o .gitmodule \t: set output file to .gitmodule")
	os.Exit(1)
}