[9front] grep: always show path with '-n'

[ori@eigenstate.org]

With the new 'g', I noticed that sometimes
we'd fail to show the filename; this happens
because 'g' now uses xargs, and if there's
exactly one file picked up by xargs, the
Hflag does not get set.

This change makes grep now print the filename
if Hflag *or* Nflag is set, which is what I'd
expect.

Before:

	% grep -n -- Nflag main.c
	106: 		flag |= Nflag;		/* count only */

After:

	% grep -n -- Nflag main.c
	main.c:106: 		flag |= Nflag;		/* count only */

And it still does something sensible for stdin:

	% grep -n asdf
	asdf
	stdin:1: asdf

Does this make sense to people?


diff 251c3cfd610abd169676852d301a2aa1267c0e57 uncommitted
--- a/sys/src/cmd/grep/main.c
+++ b/sys/src/cmd/grep/main.c
@@ -180,7 +180,7 @@
 			count++;
 			if(flag & (Cflag|Sflag|Llflag|LLflag))
 				goto cont;
-			if(flag & Hflag)
+			if(flag & (Hflag|Nflag))
 				Bprint(&bout, "%s:", file);
 			if(flag & Nflag)
 				Bprint(&bout, "%ld: ", lineno);
@@ -219,7 +219,7 @@
 			count++;
 			if(flag & (Cflag|Sflag|Llflag|LLflag))
 				goto conti;
-			if(flag & Hflag)
+			if(flag & (Hflag|Nflag))
 				Bprint(&bout, "%s:", file);
 			if(flag & Nflag)
 				Bprint(&bout, "%ld: ", lineno);