tests/test-remotefilelog-clone-tree.t

dirstate-tree: Avoid BTreeMap double-lookup when inserting a dirstate entry

The child nodes of a given node in the tree-shaped dirstate are kept in a
`BTreeMap` where keys are file names as strings. Finding or inserting a value
in the map takes `O(log(n))` string comparisons, which adds up when constructing
the tree.

The `entry` API allows finding a "spot" in the map that may or may not be
occupied and then access that value or insert a new one without doing map
lookup again. However the current API is limited in that calling `entry`
requires an owned key (and so a memory allocation), even if it ends up not
being used in the case where the map already has a value with an equal key.

This is still a win, with 4% better end-to-end time for `hg status` measured
here with hyperfine:

```
Benchmark #1: ../hg2/hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1
  Time (mean ± σ):      1.337 s ±  0.018 s    [User: 892.9 ms, System: 437.5 ms]
  Range (min … max):    1.316 s …  1.373 s    10 runs

Benchmark #2: ./hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1
  Time (mean ± σ):      1.291 s ±  0.008 s    [User: 853.4 ms, System: 431.1 ms]
  Range (min … max):    1.283 s …  1.309 s    10 runs

Summary
  './hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1' ran
    1.04 ± 0.02 times faster than '../hg2/hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1'
```

* ./hg is this revision
* ../hg2/hg is its parent
* $REPO is an old snapshot of mozilla-central

Differential Revision: https://phab.mercurial-scm.org/D10550

#require no-windows

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

  $ hg init master
  $ cd master
  $ echo treemanifest >> .hg/requires
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
# uppercase directory name to test encoding
  $ mkdir -p A/B
  $ echo x > A/B/x
  $ hg commit -qAm x

  $ cd ..

# shallow clone from full

  $ hgcloneshallow ssh://user@dummy/master shallow --noupdate
  streaming all changes
  4 files to transfer, 449 bytes of data
  transferred 449 bytes in * seconds (*/sec) (glob)
  searching for changes
  no changes found
  $ cd shallow
  $ cat .hg/requires
  dotencode
  exp-remotefilelog-repo-req-1
  fncache
  generaldelta
  persistent-nodemap (rust !)
  revlog-compression-zstd (zstd !)
  revlogv1
  sparserevlog
  store
  treemanifest
  $ find .hg/store/meta | sort
  .hg/store/meta
  .hg/store/meta/_a
  .hg/store/meta/_a/00manifest.i
  .hg/store/meta/_a/_b
  .hg/store/meta/_a/_b/00manifest.i

  $ 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)

  $ cat A/B/x
  x

  $ ls .hg/store/data
  $ echo foo > A/B/F
  $ hg add A/B/F
  $ hg ci -m 'local content'
  $ ls .hg/store/data
  ca31988f085bfb945cb8115b78fabdee40f741aa

  $ cd ..

# shallow clone from shallow

  $ hgcloneshallow ssh://user@dummy/shallow shallow2  --noupdate
  streaming all changes
  5 files to transfer, 1008 bytes of data
  transferred 1008 bytes in * seconds (*/sec) (glob)
  searching for changes
  no changes found
  $ cd shallow2
  $ cat .hg/requires
  dotencode
  exp-remotefilelog-repo-req-1
  fncache
  generaldelta
  persistent-nodemap (rust !)
  revlog-compression-zstd (zstd !)
  revlogv1
  sparserevlog
  store
  treemanifest
  $ ls .hg/store/data
  ca31988f085bfb945cb8115b78fabdee40f741aa

  $ hg update
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cat A/B/x
  x

  $ cd ..

# full clone from shallow
# - send stderr to /dev/null because the order of stdout/err causes
#   flakiness here
  $ hg clone --noupdate ssh://user@dummy/shallow full 2>/dev/null
  streaming all changes
  [100]

# getbundle full clone

  $ printf '[server]\npreferuncompressed=False\n' >> master/.hg/hgrc
  $ hgcloneshallow ssh://user@dummy/master shallow3
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 18d955ee7ba0
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ ls shallow3/.hg/store/data
  $ cat shallow3/.hg/requires
  dotencode
  exp-remotefilelog-repo-req-1
  fncache
  generaldelta
  persistent-nodemap (rust !)
  revlog-compression-zstd (zstd !)
  revlogv1
  sparserevlog
  store
  treemanifest