grep: -W: skip trailing empty lines at EOF, too

4aa2c4753d (grep: -W: don't extend context to trailing empty lines,
2016-05-28) stopped showing empty lines at the end of function context
when using -W.  Do the same for trailing empty lines at the end of
files, for consistency -- it doesn't matter whether a function section
is ended by the next function or the end of the file.

Test it by adding a trailing empty line to the file used by the test
"grep -W" and leave its expected output the same.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

grep.c

@@ -1735,7 +1735,8 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
 				peek_eol = end_of_line(peek_bol, &peek_left);
 			}
 
-			if (match_funcname(opt, gs, peek_bol, peek_eol))
+			if (peek_bol >= gs->buf + gs->size ||
+			    match_funcname(opt, gs, peek_bol, peek_eol))
 				show_function = 0;
 		}
 		if (show_function ||

t/t7810-grep.sh

@@ -31,6 +31,7 @@ int main(int argc, const char **argv)
 	return 0;
 	/* char ?? */
 }
+
 EOF
 
 test_expect_success setup '