grep: add pmatch and eflags arguments to match_one_pattern()

Push pmatch and eflags to the callers of match_one_pattern(), which
allows them to specify regex execution flags and to get the location
of a match.

Since we only use the first element of the matches array and aren't
interested in submatches, no provision is made for callers to
provide a larger array.

eflags are ignored for fixed patterns, but that's OK, since they
only have a meaning in connection with regular expressions
containing ^ or $.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

grep.c

@@ -309,11 +309,11 @@ static struct {
 };
 
 static int match_one_pattern(struct grep_pat *p, char *bol, char *eol,
-			     enum grep_context ctx)
+			     enum grep_context ctx,
+			     regmatch_t *pmatch, int eflags)
 {
 	int hit = 0;
 	int saved_ch = 0;
-	regmatch_t pmatch[10];
 
 	if ((p->token != GREP_PATTERN) &&
 	    ((p->token == GREP_PATTERN_HEAD) != (ctx == GREP_CONTEXT_HEAD)))
@@ -332,14 +332,10 @@ static int match_one_pattern(struct grep_pat *p, char *bol, char *eol,
 	}
 
  again:
-	if (!p->fixed) {
-		regex_t *exp = &p->regexp;
-		hit = !regexec(exp, bol, ARRAY_SIZE(pmatch),
-			       pmatch, 0);
-	}
-	else {
+	if (p->fixed)
 		hit = !fixmatch(p->pattern, bol, pmatch);
-	}
+	else
+		hit = !regexec(&p->regexp, bol, 1, pmatch, eflags);
 
 	if (hit && p->word_regexp) {
 		if ((pmatch[0].rm_so < 0) ||
@@ -385,10 +381,11 @@ static int match_expr_eval(struct grep_expr *x, char *bol, char *eol,
 			   enum grep_context ctx, int collect_hits)
 {
 	int h = 0;
+	regmatch_t match;
 
 	switch (x->node) {
 	case GREP_NODE_ATOM:
-		h = match_one_pattern(x->u.atom, bol, eol, ctx);
+		h = match_one_pattern(x->u.atom, bol, eol, ctx, &match, 0);
 		break;
 	case GREP_NODE_NOT:
 		h = !match_expr_eval(x->u.unary, bol, eol, ctx, 0);
@@ -427,12 +424,14 @@ static int match_line(struct grep_opt *opt, char *bol, char *eol,
 		      enum grep_context ctx, int collect_hits)
 {
 	struct grep_pat *p;
+	regmatch_t match;
+
 	if (opt->extended)
 		return match_expr(opt, bol, eol, ctx, collect_hits);
 
 	/* we do not call with collect_hits without being extended */
 	for (p = opt->pattern_list; p; p = p->next) {
-		if (match_one_pattern(p, bol, eol, ctx))
+		if (match_one_pattern(p, bol, eol, ctx, &match, 0))
 			return 1;
 	}
 	return 0;