MAN page

[trypy]

Maybe add MAN page to github for potential edits

I see in code --check returns three possible values.

Maybe note this in MAN page and/or --help text

const char *check_status_str(int check) { switch (check) { case 1: return "OK"; case 2: return "WARNING"; case 3: return "ERROR"; }

return "";

}

[tjko]

Man page is included in the repository: https://github.com/tjko/jpeginfo/blob/master/jpeginfo.1

I added note about the exit code in the man page (https://github.com/tjko/jpeginfo/commit/6bcb601dd063102d4654f2724681cdd156561c1e)