Sync with Git 2.20.1

* maint:
  Git 2.20.1
  .gitattributes: ensure t/oid-info/* has eol=lf
  t9902: 'send-email' test case requires PERL
  t4256: mark support files as LF-only
  parse-options: fix SunCC compiler warning
  help -a: handle aliases with long names gracefully
  help.h: fix coding style
  run-command: report exec failure