K 10
svn:author
V 6
kevans
K 8
svn:date
V 27
2021-02-11T15:23:09.354876Z
K 7
svn:log
V 1055
grep: fix null pattern and empty pattern file behavior

The null pattern semantics were terrible because I tried to match gnugrep,
but I got it wrong.  Let's unwind that:

- The null pattern should match every line if neither -w nor -x.
- The null pattern should match empty lines if -x.
- The null pattern should not match any lines if -w.

The first two will stop processing (shortcut) even if additional patterns
are specified. In any other case, we will continue processing other
patterns.  If no other patterns are specified beside a null pattern, then
we match if neither -w nor -x or set and do not match if either of those
are specified.

The justification for -w is that it should match on a whole word, but the
null pattern deos not have a whole word to match on.

Empty pattern files should never match anything, and more importantly, -v
should cause everything to be written.

PR:		253209

(cherry picked from commit f823c6dc730b0dd08b54a53be1d8fd587eee7021)

Git Hash:   92ddb6090b0c5091a64855a514676a452c10750c
Git Author: kevans@FreeBSD.org
END