Implement get last version only option

nix-headbump.go

@@ -14,11 +14,14 @@ import (
 
 const version string = "0.1.0"
 
+var re = regexp.MustCompile(`(?s)(import\s+\(fetchTarball\s+"https://github.com/NixOS/nixpkgs/archive/)([^"]+?)(\.tar\.gz"\))`)
+
 var revision string
 
 func main() {
 	versionFlag := flag.Bool("version", false, "print the version of this program")
 	currentFlag := flag.Bool("current", false, "print current nixpath without bumping")
+	lastFlag := flag.Bool("last", false, "print git head ref without bumping")
 	flag.Parse()
 
 	if *versionFlag {
@@ -44,7 +47,15 @@ func main() {
 			fmt.Println(current)
 			return
 		}
-		err := bump(path)
+		last, err := getLastVersion()
+		if err != nil {
+			log.Fatalf("Getting the last version has been failed: %s", err.Error())
+		}
+		if *lastFlag {
+			fmt.Println(last)
+			return
+		}
+		err = bump(path, last)
 		if err != nil {
 			log.Fatalf("Bumping the version has been failed: %s", err.Error())
 		}
@@ -53,51 +64,53 @@ func main() {
 	}
 }
 
-type Commit struct {
-	Sha string `json:"sha"`
-}
+func bump(path string, last string) error {
+	origin, err := os.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	replaced := re.ReplaceAll(origin, []byte("${1}"+last+"${3}"))
+	if bytes.Equal(origin, replaced) {
+		return nil
+	}
 
-type Response struct {
-	Commit Commit `json:"commit"`
+	return os.WriteFile(path, replaced, os.ModePerm)
 }
 
-var re = regexp.MustCompile(`(?s)(import\s+\(fetchTarball\s+"https://github.com/NixOS/nixpkgs/archive/)([^"]+?)(\.tar\.gz"\))`)
-
-func bump(path string) error {
+func getCurrentVersion(path string) (string, error) {
 	origin, err := os.ReadFile(path)
 	if err != nil {
-		return err
+		return "", err
+	}
+	matches := re.FindStringSubmatch(string(origin))
+	return matches[2], nil
+}
+
+func getLastVersion() (string, error) {
+	type commit struct {
+		Sha string `json:"sha"`
+	}
+
+	type response struct {
+		Commit commit `json:"commit"`
 	}
+
 	req, _ := http.NewRequest("GET", "https://api.github.com/repos/NixOS/nixpkgs/branches/master", nil)
 	req.Header.Set("Accept", "application/vnd.github+json")
 	req.Header.Set("X-GitHub-Api-Version", "2022-11-28")
 	client := new(http.Client)
 	res, err := client.Do(req)
 	if err != nil {
-		return err
+		return "", err
 	}
 	defer res.Body.Close()
 	body, err := io.ReadAll(res.Body)
 	if err != nil {
-		return err
+		return "", err
 	}
-	jsonRes := &Response{}
+	jsonRes := &response{}
 	if json.Unmarshal(body, jsonRes) != nil {
-		return err
-	}
-	replaced := re.ReplaceAll(origin, []byte("${1}"+jsonRes.Commit.Sha+"${3}"))
-	if bytes.Equal(origin, replaced) {
-		return nil
-	}
-
-	return os.WriteFile(path, replaced, os.ModePerm)
-}
-
-func getCurrentVersion(path string) (string, error) {
-	origin, err := os.ReadFile(path)
-	if err != nil {
 		return "", err
 	}
-	matches := re.FindStringSubmatch(string(origin))
-	return matches[2], nil
+	return jsonRes.Commit.Sha, nil
 }