Fix EMFILE too many open files

[nodkz]

This fix helps to avoid too many open files error for big repositories:

[Error: EMFILE: too many open files, open '/mnt/vss/_work/1/s/repo/.git/refs/remotes/origin/some-branch'] {
  errno: -24,
  code: 'EMFILE',
  syscall: 'open',
  path: '/mnt/vss/_work/1/s/repo/.git/refs/remotes/origin/some-branch'
}