fix: branch checking logic

See https://github.com/go-git/go-git/issues/518 for why this is needed.

pkg/git/branch.go

@@ -5,6 +5,25 @@ import (
 	"github.com/go-git/go-git/v5/plumbing"
 )
 
+// Check if a branch exists in a repo.
+// Use this and not repository.Branch(), because the latter does not
+// actually check for existing branches.
+// See https://github.com/go-git/go-git/issues/518
+func HasBranch(repository *git.Repository, name string) bool {
+	var exist bool
+	if iter, err := repository.Branches(); err == nil {
+		iterFunc := func(reference *plumbing.Reference) error {
+			if name == reference.Name().Short() {
+				exist = true
+				return nil
+			}
+			return nil
+		}
+		_ = iter.ForEach(iterFunc)
+	}
+	return exist
+}
+
 // GetCurrentBranch retrieves the current branch of a repository
 func GetCurrentBranch(repository *git.Repository) (string, error) {
 	branchRefs, err := repository.Branches()