reset: support the `--pathspec-from-file` option

reset: support the `--pathspec-from-file` option

Decisions taken for simplicity:
1) For now, `--pathspec-from-file` is declared incompatible with
   `--patch`, even when <file> is not `stdin`. Such use case it not
   really expected. Also, it is harder to support in `git commit`, so
   I decided to make it incompatible in all places.
2) It is not allowed to pass pathspec in both args and file.

Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>