Check if git support --initial-branch before attempting to use it on init

`git init --initial-branch` was only added in git
version 0.28.0. We parse the git version and
check if the argument is supported before using it
Fixes #8

git/client.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/badjware/gitlabfs/fstree"
+	"github.com/badjware/gitlabfs/utils"
 	"github.com/vmihailenco/taskq/v3"
 	"github.com/vmihailenco/taskq/v3/memqueue"
 )
@@ -29,6 +30,10 @@ type gitClient struct {
 
 	hostnameProg *regexp.Regexp
 
+	majorVersion int
+	minorVersion int
+	patchVersion string
+
 	queue     taskq.Queue
 	cloneTask *taskq.Task
 	pullTask  *taskq.Task
@@ -50,6 +55,25 @@ func NewClient(p GitClientParam) (*gitClient, error) {
 		}),
 	}
 
+	// Parse git version
+	gitVersionOutput, err := utils.ExecProcess("git", "--version")
+	if err != nil {
+		return nil, fmt.Errorf("failed to run \"git --version\": %v", err)
+	}
+	prog := regexp.MustCompile(`([0-9]+)\.([0-9]+)\.(.+)`)
+	gitVersionMatches := prog.FindStringSubmatch(gitVersionOutput)
+	c.majorVersion, err = strconv.Atoi(gitVersionMatches[1])
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse git major version \"%v\": %v", gitVersionOutput, err)
+	}
+	c.minorVersion, err = strconv.Atoi(gitVersionMatches[2])
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse git minor version \"%v\": %v", gitVersionOutput, err)
+	}
+	c.patchVersion = gitVersionMatches[3]
+	fmt.Printf("Detected git version: major = %v minor = %v patch = %v\n", c.majorVersion, c.minorVersion, c.patchVersion)
+
+	// Register tasks
 	c.cloneTask = taskq.RegisterTask(&taskq.TaskOptions{
 		Name:       "git-clone",
 		Handler:    c.clone,

git/clone.go

@@ -16,12 +16,19 @@ func (c *gitClient) clone(url string, defaultBranch string, dst string) error {
 
 		// Init the local repo
 		fmt.Printf("Initializing %v into %v\n", url, dst)
-		_, err := utils.ExecProcess(
-			"git", "init",
-			"--initial-branch", defaultBranch,
+		args := []string{
+			"init",
+		}
+		if c.majorVersion > 2 || c.majorVersion == 2 && c.minorVersion >= 28 {
+			args = append(args, "--initial-branch", defaultBranch)
+		} else {
+			fmt.Printf("Version of git is too old to support --initial-branch. Consider upgrading git to version >= 2.28.0")
+		}
+		args = append(args,
 			"--",
 			dst, // directory
 		)
+		_, err := utils.ExecProcess("git", args...)
 		if err != nil {
 			return fmt.Errorf("failed to init git repo %v to %v: %v", url, dst, err)
 		}