on master:

Impossible to list history/ for more than a few hundreds commits because ls
getdents() syscalls are done with a quite small buffer (19 entries on my
machine), hence the readdir is regularly called with a different offset and the
directories entries are re-computed every time.

on feature/add-direntry-lru-cache:

- medium repo (13k commits)
    1s          (no cache)
    0.2s        (cached)
- very large repo (900k commits)
    6min24s     (no cache)
    4min34s     (cached)