Merge branch 'rs/ring-buffer-wraparound' into next

The code that we have used for the past 10+ years to cycle
4-element ring buffers turns out to be not quite portable in
theoretical world.

* rs/ring-buffer-wraparound:
  hex: make wraparound of the index into ring-buffer explicit

Author: gitster

hex.c

@@ -78,7 +78,8 @@ char *sha1_to_hex(const unsigned char *sha1)
 {
 	static int bufno;
 	static char hexbuffer[4][GIT_SHA1_HEXSZ + 1];
-	return sha1_to_hex_r(hexbuffer[3 & ++bufno], sha1);
+	bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
+	return sha1_to_hex_r(hexbuffer[bufno], sha1);
 }
 
 char *oid_to_hex(const struct object_id *oid)

path.c

@@ -25,7 +25,8 @@ static struct strbuf *get_pathname(void)
 		STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
 	};
 	static int index;
-	struct strbuf *sb = &pathname_array[3 & ++index];
+	struct strbuf *sb = &pathname_array[index];
+	index = (index + 1) % ARRAY_SIZE(pathname_array);
 	strbuf_reset(sb);
 	return sb;
 }