Merge branch 'en/clean-nested-with-ignored'
"git clean" fixes.
* en/clean-nested-with-ignored:
dir: special case check for the possibility that pathspec is NULL
clean: fix theoretical path corruption
clean: rewrap overly long line
clean: avoid removing untracked files in a nested git repository
clean: disambiguate the definition of -d
git-clean.txt: do not claim we will delete files with -n/--dry-run
dir: add commentary explaining match_pathspec_item's return value
dir: if our pathspec might match files under a dir, recurse into it
dir: make the DO_MATCH_SUBMODULE code reusable for a non-submodule case
dir: also check directories for matching pathspecs
dir: fix off-by-one error in match_pathspec_item
dir: fix typo in comment
t7300: add testcases showing failure to clean specified pathspecs