tests/test-remotefilelog-bundle2-legacy.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"

generaldelta to generaldelta interactions with bundle2 but legacy clients
without changegroup2 support
  $ cat > testcg2.py << EOF
  > import sys
  > from mercurial import changegroup, registrar, util
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command('testcg2', norepo=True)
  > def testcg2(ui):
  >     if not util.safehasattr(changegroup, 'cg2packer'):
  >         sys.exit(80)
  > EOF
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > testcg2 = $TESTTMP/testcg2.py
  > EOF
  $ hg testcg2 || exit 80

  $ cat > disablecg2.py << EOF
  > from mercurial import changegroup, error, util
  > deleted = False
  > def reposetup(ui, repo):
  >     global deleted
  >     if deleted:
  >         return
  >     packermap = changegroup._packermap
  >     # protect against future changes
  >     if len(packermap) != 3:
  >         raise error.Abort('packermap has %d versions, expected 3!' % len(packermap))
  >     for k in ['01', '02', '03']:
  >         if not packermap.get(k):
  >             raise error.Abort("packermap doesn't have key '%s'!" % k)
  > 
  >     del packermap['02']
  >     deleted = True
  > EOF

  $ hg init master
  $ grep generaldelta master/.hg/requires
  generaldelta
  $ cd master
preferuncompressed = False so that we can make both generaldelta and non-generaldelta clones
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > [experimental]
  > bundle2-exp = True
  > [server]
  > preferuncompressed = False
  > EOF
  $ echo x > x
  $ hg commit -qAm x

  $ cd ..

  $ hgcloneshallow ssh://user@dummy/master shallow -q --pull --config experimental.bundle2-exp=True
  1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
  $ cd shallow
  $ cat >> .hg/hgrc << EOF
  > [extensions]
  > disablecg2 = $TESTTMP/disablecg2.py
  > EOF

  $ cd ../master
  $ echo y > y
  $ hg commit -qAm y

  $ cd ../shallow
  $ hg pull -u
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets d34c38483be9
  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)

  $ echo a > a
  $ hg commit -qAm a
  $ hg push
  pushing to ssh://user@dummy/master
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files