trailer: use size_t for iterating trailer list

We store the length of the trailers list in a size_t. So on
a 64-bit system with a 32-bit int, in the unlikely case that
we manage to actually allocate a list with 2^31 entries,
we'd loop forever trying to iterate over it (our "int" would
wrap to negative before exceeding info->trailer_nr).

This probably doesn't matter in practice. Each entry is at
least a pointer plus a non-empty string, so even without
malloc overhead or the memory to hold the original string
we're parsing from, you'd need to allocate tens of
gigabytes. But it's easy enough to do it right.

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

sequencer.c

@@ -225,7 +225,7 @@ static int has_conforming_footer(struct strbuf *sb, struct strbuf *sob,
 	int ignore_footer)
 {
 	struct trailer_info info;
-	int i;
+	size_t i;
 	int found_sob = 0, found_sob_last = 0;
 
 	trailer_info_get(&info, sb->buf);

trailer.c

@@ -948,7 +948,7 @@ static size_t process_input_file(FILE *outfile,
 	struct trailer_info info;
 	struct strbuf tok = STRBUF_INIT;
 	struct strbuf val = STRBUF_INIT;
-	int i;
+	size_t i;
 
 	trailer_info_get(&info, str);
 
@@ -1112,7 +1112,7 @@ void trailer_info_get(struct trailer_info *info, const char *str)
 
 void trailer_info_release(struct trailer_info *info)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < info->trailer_nr; i++)
 		free(info->trailers[i]);
 	free(info->trailers);
@@ -1122,7 +1122,7 @@ static void format_trailer_info(struct strbuf *out,
 				const struct trailer_info *info,
 				const struct process_trailer_options *opts)
 {
-	int i;
+	size_t i;
 
 	/* If we want the whole block untouched, we can take the fast path. */
 	if (!opts->only_trailers && !opts->unfold) {