strbuf: use size_t for length in intermediate variables

A few strbuf functions store the length of a strbuf in a
temporary variable. We should always use size_t for this, as
it's possible for a strbuf to exceed an "int" (e.g., a 2GB
string on a 64-bit system). This is unlikely in practice,
but we should try to behave sensibly on silly or malicious
input.

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

strbuf.c

@@ -209,7 +209,7 @@ void strbuf_list_free(struct strbuf **sbs)
 
 int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
 {
-	int len = a->len < b->len ? a->len: b->len;
+	size_t len = a->len < b->len ? a->len: b->len;
 	int cmp = memcmp(a->buf, b->buf, len);
 	if (cmp)
 		return cmp;
@@ -389,7 +389,7 @@ size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
 
 void strbuf_addbuf_percentquote(struct strbuf *dst, const struct strbuf *src)
 {
-	int i, len = src->len;
+	size_t i, len = src->len;
 
 	for (i = 0; i < len; i++) {
 		if (src->buf[i] == '%')
@@ -960,7 +960,7 @@ static size_t cleanup(char *line, size_t len)
  */
 void strbuf_stripspace(struct strbuf *sb, int skip_comments)
 {
-	int empties = 0;
+	size_t empties = 0;
 	size_t i, j, len, newlen;
 	char *eol;