Merge branch 'dl/stash-show-untracked-fixup'

The code to handle options recently added to "git stash show"
around untracked part of the stash segfaulted when these options
were used on a stash entry that does not record untracked part.

* dl/stash-show-untracked-fixup:
  stash show: fix segfault with --{include,only}-untracked
  t3905: correct test title

diff --cc builtin/stash.c
Simple merge

diff --cc t/t3905-stash-include-untracked.sh
Simple merge