Make "sync branch" also sync object format and add tests (#30878) (#30880)

Backport #30878 by wxiaoguang

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/git/repo.go

@@ -7,7 +7,6 @@ package git
 import (
 	"bytes"
 	"context"
-	"errors"
 	"fmt"
 	"io"
 	"net/url"
@@ -63,32 +62,6 @@ func IsRepoURLAccessible(ctx context.Context, url string) bool {
 	return err == nil
 }
 
-// GetObjectFormatOfRepo returns the hash type of repository at a given path
-func GetObjectFormatOfRepo(ctx context.Context, repoPath string) (ObjectFormat, error) {
-	var stdout, stderr strings.Builder
-
-	err := NewCommand(ctx, "hash-object", "--stdin").Run(&RunOpts{
-		Dir:    repoPath,
-		Stdout: &stdout,
-		Stderr: &stderr,
-		Stdin:  &strings.Reader{},
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	if stderr.Len() > 0 {
-		return nil, errors.New(stderr.String())
-	}
-
-	h, err := NewIDFromString(strings.TrimRight(stdout.String(), "\n"))
-	if err != nil {
-		return nil, err
-	}
-
-	return h.Type(), nil
-}
-
 // InitRepository initializes a new Git repository.
 func InitRepository(ctx context.Context, repoPath string, bare bool, objectFormatName string) error {
 	err := os.MkdirAll(repoPath, os.ModePerm)