fix(grep): fix git-grep for code search when git version is below 2.38

(cherry picked from commit f2ab4ff83a)

Conflicts:
	modules/git/grep.go
  trivial context conflict

modules/git/grep.go

@@ -17,6 +17,7 @@ import (
 	"strings"
 	"time"
 
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 )
 
@@ -30,7 +31,7 @@ type GrepResult struct {
 type GrepOptions struct {
 	RefName           string
 	MaxResultLimit    int
-	MatchesPerFile    int
+	MatchesPerFile    int // >= git 2.38
 	ContextLineNumber int
 	IsFuzzy           bool
 	PathSpec          []setting.Glob
@@ -77,7 +78,14 @@ func GrepSearch(ctx context.Context, repo *Repository, search string, opts GrepO
 		"-I", "--null", "--break", "--heading", "--column",
 		"--fixed-strings", "--line-number", "--ignore-case", "--full-name")
 	cmd.AddOptionValues("--context", fmt.Sprint(opts.ContextLineNumber))
+
+	// --max-count requires at least git 2.38
+	if CheckGitVersionAtLeast("2.38.0") == nil {
 		cmd.AddOptionValues("--max-count", fmt.Sprint(opts.MatchesPerFile))
+	} else {
+		log.Warn("git-grep: --max-count requires at least git 2.38")
+	}
+
 	words := []string{search}
 	if opts.IsFuzzy {
 		words = strings.Fields(search)