revisions: initialize revs->grep_filter using grep_init()

Instead of using the hand-rolled initialization sequence,
use grep_init() to populate the necessary bits.  This opens
the door to allow the calling commands to optionally read
grep.* configuration variables via git_config() if they
want to.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

grep.c

@@ -16,6 +16,11 @@ static struct grep_opt grep_defaults;
 void init_grep_defaults(void)
 {
 	struct grep_opt *opt = &grep_defaults;
+	static int run_once;
+
+	if (run_once)
+		return;
+	run_once++;
 
 	memset(opt, 0, sizeof(*opt));
 	opt->relative = 1;

revision.c

@@ -1048,9 +1048,9 @@ void init_revisions(struct rev_info *revs, const char *prefix)
 
 	revs->commit_format = CMIT_FMT_DEFAULT;
 
+	init_grep_defaults();
+	grep_init(&revs->grep_filter, prefix);
 	revs->grep_filter.status_only = 1;
-	revs->grep_filter.pattern_tail = &(revs->grep_filter.pattern_list);
-	revs->grep_filter.header_tail = &(revs->grep_filter.header_list);
 	revs->grep_filter.regflags = REG_NEWLINE;
 
 	diff_setup(&revs->diffopt);
@@ -1893,6 +1893,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	revs->diffopt.abbrev = revs->abbrev;
 	diff_setup_done(&revs->diffopt);
 
+	grep_commit_pattern_type(GREP_PATTERN_TYPE_UNSPECIFIED,
+				 &revs->grep_filter);
 	compile_grep_patterns(&revs->grep_filter);
 
 	if (revs->reverse && revs->reflog_info)