record_author_date(): use find_commit_header()

This saves us some manual parsing and makes the code more
readable.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit.c

@@ -584,25 +584,19 @@ define_commit_slab(author_date_slab, unsigned long);
 static void record_author_date(struct author_date_slab *author_date,
 			       struct commit *commit)
 {
-	const char *buf, *line_end, *ident_line;
 	const char *buffer = get_commit_buffer(commit, NULL);
 	struct ident_split ident;
+	const char *ident_line;
+	size_t ident_len;
 	char *date_end;
 	unsigned long date;
 
-	for (buf = buffer; buf; buf = line_end + 1) {
-		line_end = strchrnul(buf, '\n');
-		if (!skip_prefix(buf, "author ", &ident_line)) {
-			if (!line_end[0] || line_end[1] == '\n')
-				goto fail_exit; /* end of header */
-			continue;
-		}
-		if (split_ident_line(&ident,
-				     ident_line, line_end - ident_line) ||
-		    !ident.date_begin || !ident.date_end)
-			goto fail_exit; /* malformed "author" line */
-		break;
-	}
+	ident_line = find_commit_header(buffer, "author", &ident_len);
+	if (!ident_line)
+		goto fail_exit; /* no author line */
+	if (split_ident_line(&ident, ident_line, ident_len) ||
+	    !ident.date_begin || !ident.date_end)
+		goto fail_exit; /* malformed "author" line */
 
 	date = strtoul(ident.date_begin, &date_end, 10);
 	if (date_end != ident.date_end)