Keep compatibility with Git below 2.28

Thanks to Alois Micard for pointing that out

make.go

@@ -392,7 +392,16 @@ func createGitRepository(debsrc, gopkg, orig string, u *upstream,
 		return "", err
 	}
 
-	if err := runGitCommandIn(dir, "init", "-b", debianBranch); err != nil {
+	// "git init -b" is the one-liner we need here, however it was added in Git 2.28.
+	// For now we prefer to keep compatibility with older Git, so we do it in two
+	// rounds, "git init" then "git checkout".
+	//if err := runGitCommandIn(dir, "init", "-b", debianBranch); err != nil {
+	//	return dir, err
+	//}
+	if err := runGitCommandIn(dir, "init"); err != nil {
+		return dir, err
+	}
+	if err := runGitCommandIn(dir, "checkout", "-q", "-b", debianBranch); err != nil {
 		return dir, err
 	}