WIP: the beginning of catalogue generation

See coop-cloud/organising#159.

pkg/git/clone.go

@@ -1,9 +1,12 @@
 package git
 
 import (
+	"fmt"
 	"os"
+	"strings"
 
 	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/config"
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/sirupsen/logrus"
 )
@@ -15,7 +18,6 @@ func Clone(dir, url string) error {
 		_, err := git.PlainClone(dir, false, &git.CloneOptions{URL: url, Tags: git.AllTags})
 		if err != nil {
 			logrus.Debugf("cloning from default branch failed, attempting from main branch")
-			// try with main branch because Git is being a Git
 			_, err := git.PlainClone(dir, false, &git.CloneOptions{
 				URL:           url,
 				Tags:          git.AllTags,
@@ -25,9 +27,66 @@ func Clone(dir, url string) error {
 				return err
 			}
 		}
+		logrus.Debugf("'%s' has been git cloned successfully", dir)
+	} else {
+		logrus.Debugf("'%s' already exists, doing nothing", dir)
 	}
 
-	logrus.Debugf("'%s' has been git cloned successfully", dir)
-
+	return nil
+}
+
+// EnsureUpToDate ensures that a git repo on disk has the latest changes (git-fetch).
+func EnsureUpToDate(dir string) error {
+	repo, err := git.PlainOpen(dir)
+	if err != nil {
+		return err
+	}
+
+	branch := "master"
+	if _, err := repo.Branch("master"); err != nil {
+		if _, err := repo.Branch("main"); err != nil {
+			return err
+		}
+		branch = "main"
+	}
+
+	logrus.Debugf("choosing '%s' as main git branch for in '%s'", branch, dir)
+
+	worktree, err := repo.Worktree()
+	if err != nil {
+		return err
+	}
+
+	refName := fmt.Sprintf("refs/heads/%s", branch)
+	checkOutOpts := &git.CheckoutOptions{
+		Create: false,
+		Force:  true,
+		Keep:   false,
+		Branch: plumbing.ReferenceName(refName),
+	}
+	if err := worktree.Checkout(checkOutOpts); err != nil {
+		return err
+	}
+
+	logrus.Debugf("successfully checked out '%s'", branch)
+
+	remote, err := repo.Remote("origin")
+	if err != nil {
+		return err
+	}
+
+	fetchOpts := &git.FetchOptions{
+		RemoteName: "origin",
+		RefSpecs:   []config.RefSpec{"refs/heads/*:refs/remotes/origin/*"},
+		Force:      true,
+	}
+	if err := remote.Fetch(fetchOpts); err != nil {
+		if !strings.Contains(err.Error(), "already up-to-date") {
+			return err
+		}
+	}
+
+	logrus.Debugf("successfully fetched all changes in '%s'", dir)
+
 	return nil
 }