tests/test-remotefilelog-permissions.t

treemanifest: stop storing full path for each item in manifest._lazydirs

This information is obtainable, if needed, based on the lazydirs key (which is
the entry name) and the manifest's `dir()` method.

### Performance

This is actually both a memory and a performance improvement, but it's likely to
be a very small one in most situations. In the pathological repo I've been using
for testing other performance work I've done recently, this reduced the time for
a rebase operation (rebasing two commits across a public-phase change that
touches a sibling of one of my tracked directories where the common parent is
massive (>>10k entries)):

#### Before

```
  Time (mean ± σ):      4.059 s ±  0.121 s    [User: 0.9 ms, System: 0.6 ms]
  Range (min … max):    3.941 s …  4.352 s    10 runs
```

#### After

```
  Time (mean ± σ):      3.707 s ±  0.060 s    [User: 0.8 ms, System: 0.8 ms]
  Range (min … max):    3.648 s …  3.818 s    10 runs
```

Differential Revision: https://phab.mercurial-scm.org/D9553

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ hg commit -qAm x

  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)

  $ cd master
  $ echo xx > x
  $ hg commit -qAm x2
  $ cd ..

# Test cache misses with read only permissions on server

  $ chmod -R a-w master/.hg/remotefilelogcache
  $ cd shallow
  $ hg pull -q
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd ..

  $ chmod -R u+w master/.hg/remotefilelogcache

# Test setting up shared cache with the right permissions
# (this is hard to test in a cross platform way, so we just make sure nothing
# crashes)

  $ rm -rf $CACHEDIR
  $ umask 002
  $ mkdir $CACHEDIR
  $ hg -q clone --shallow ssh://user@dummy/master shallow2 --config remotefilelog.cachegroup="`id -g -n`"
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over * (glob)
  $ ls -ld $CACHEDIR/11
  drwxrws* $TESTTMP/hgcache/11 (glob)