pack-revindex.h: correct the time complexity descriptions

Time complexities for pack_pos_to_midx and midx_to_pack_pos are swapped,
correct it.

Signed-off-by: Kyle Zhao <[email protected]>
Reviewed-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: keyu98

pack-revindex.h

@@ -109,7 +109,7 @@ off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos);
  * If the reverse index has not yet been loaded, or the position is out of
  * bounds, this function aborts.
  *
- * This function runs in time O(log N) with the number of objects in the MIDX.
+ * This function runs in constant time.
  */
 uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos);
 
@@ -120,7 +120,7 @@ uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos);
  * If the reverse index has not yet been loaded, or the position is out of
  * bounds, this function aborts.
  *
- * This function runs in constant time.
+ * This function runs in time O(log N) with the number of objects in the MIDX.
  */
 int midx_to_pack_pos(struct multi_pack_index *midx, uint32_t at, uint32_t *pos);