support gitmailmap in GetCodeActivityStats() (#15009)

ref:
- https://git-scm.com/docs/gitmailmap
- https://git-scm.com/docs/git-log#Documentation/git-log.txt-emaNem

Signed-off-by: a1012112796 <1012112796@qq.com>

Co-authored-by: zeripath <art27@cantab.net>

modules/git/repo_stats.go

@@ -59,7 +59,7 @@ func (repo *Repository) GetCodeActivityStats(fromTime time.Time, branch string)
 		_ = stdoutWriter.Close()
 	}()
 
-	args := []string{"log", "--numstat", "--no-merges", "--pretty=format:---%n%h%n%an%n%ae%n", "--date=iso", fmt.Sprintf("--since='%s'", since)}
+	args := []string{"log", "--numstat", "--no-merges", "--pretty=format:---%n%h%n%aN%n%aE%n", "--date=iso", fmt.Sprintf("--since='%s'", since)}
 	if len(branch) == 0 {
 		args = append(args, "--branches=*")
 	} else {