2018-04-26 - Golang Phoenix - Package Madness! - https://www.meetup.com/Golang-Phoenix/events/249838312/

main.go

package main

// https://www.meetup.com/Golang-Phoenix/events/249838312/
// I was assigned the 'gopkg.in/src-d/go-git.v4' package. Below is a simple program that will take a Git URL,
// clone the repo, and scan SemVer-compliant tags then output the most recent, as per SemVer, version.

import (
	"fmt"
	"io/ioutil"
	"os"
	"strings"

	"github.com/blang/semver"

	git "gopkg.in/src-d/go-git.v4"
	"gopkg.in/src-d/go-git.v4/plumbing"
)

func main() {
	tmp, err := ioutil.TempDir("", "")
	if err != nil {
		panic(err)
	}

	url := "https://github.com/src-d/go-git"
	if len(os.Args) > 1 {
		url = os.Args[1]
	}

	repo, err := git.PlainClone(tmp, false, &git.CloneOptions{
		URL:      url,
		Progress: nil,
	})
	if err != nil {
		panic(err)
	}

	iter, err := repo.Tags()
	if err != nil {
		panic(err)
	}

	var latest *semver.Version

	err = iter.ForEach(func(ref *plumbing.Reference) (err error) {
		strs := ref.Strings()
		name := strings.TrimPrefix(strs[0], "refs/tags/v")

		if i := strings.LastIndex(name, "refs/tags"); i < 0 {
			version := semver.MustParse(name)
			if latest == nil || latest.Compare(version) < 0 {
				latest = &version
			}
		}
		return
	})
	if err != nil {
		panic(err)
	}

	fmt.Fprintf(os.Stdout, "%s: %s\n", url, latest)
}