Merge branch 'jc/ustar-checksum-is-unsigned' into maint

"git archive" incorrectly computed the header checksum; the symptom
was observed only when using pathnames with hi-bit set.

* jc/ustar-checksum-is-unsigned:
  archive: ustar header checksum is computed unsigned

archive-tar.c

@@ -139,13 +139,13 @@ static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
 
 static unsigned int ustar_header_chksum(const struct ustar_header *header)
 {
-	const char *p = (const char *)header;
+	const unsigned char *p = (const unsigned char *)header;
 	unsigned int chksum = 0;
-	while (p < header->chksum)
+	while (p < (const unsigned char *)header->chksum)
 		chksum += *p++;
 	chksum += sizeof(header->chksum) * ' ';
 	p += sizeof(header->chksum);
-	while (p < (const char *)header + sizeof(struct ustar_header))
+	while (p < (const unsigned char *)header + sizeof(struct ustar_header))
 		chksum += *p++;
 	return chksum;
 }