Merge branch 'it/fetch-pack-many-refs'

Merge branch 'it/fetch-pack-many-refs'

When "git fetch" encounters repositories with too many references, the
command line of "fetch-pack" that is run by a helper e.g. remote-curl,
may fail to hold all of them. Now such an internal invocation can feed
the references through the standard input of "fetch-pack".

By Ivan Todoroski
* it/fetch-pack-many-refs:
  remote-curl: main test case for the OS command line overflow
  fetch-pack: test cases for the new --stdin option
  remote-curl: send the refs to fetch-pack on stdin
  fetch-pack: new --stdin option to read refs from stdin