tests/test-hooklib-changeset_published.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

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > notify =
  > hooklib =
  > 
  > [phases]
  > publish = False
  > 
  > [notify]
  > sources = pull
  > diffstat = False
  > messageidseed = example
  > domain = example.com
  > 
  > [reposubs]
  > * = baz
  > EOF
  $ hg init a
  $ hg --cwd a debugbuilddag .
  $ hg init b
  $ cat <<EOF >> b/.hg/hgrc
  > [hooks]
  > incoming.notify = python:hgext.notify.hook
  > txnclose-phase.changeset_published = python:hgext.hooklib.changeset_published.hook
  > EOF
  $ hg --cwd b pull ../a | "$PYTHON" $TESTDIR/unwrap-message-id.py
  pulling from ../a
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets 1ea73414a91b (1 drafts)
  MIME-Version: 1.0
  Content-Type: text/plain; charset="us-ascii"
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: changeset in * (glob)
  From: [e-mail]
  X-Hg-Notification: changeset 1ea73414a91b
  Message-Id: <hg.[e-mail]>
  To: [e-mail]
  
  changeset 1ea73414a91b in $TESTTMP/b
  details: $TESTTMP/b?cmd=changeset;node=1ea73414a91b
  description:
  	r0
  (run 'hg update' to get a working copy)
  $ hg --cwd a phase --public 0
  $ hg --cwd b pull ../a | "$PYTHON" $TESTDIR/unwrap-message-id.py
  pulling from ../a
  searching for changes
  no changes found
  1 local changesets published
  Subject: changeset published
  In-reply-to: <hg.[e-mail]>
  Message-Id: <hg.[e-mail]>
  Date: * (glob)
  From: [e-mail]
  To: [e-mail]
  
  This changeset has been published.
  $ hg --cwd b phase --force --draft 0
  $ cat <<EOF >> b/.hg/hgrc
  > [notify_published]
  > messageidseed = example2
  > domain = alt.example.com
  > template = Subject: changeset published
  >            From: [e-mail]\n
  >            This draft changeset has been published.\n
  > EOF
  $ hg --cwd b pull ../a | "$PYTHON" $TESTDIR/unwrap-message-id.py
  pulling from ../a
  searching for changes
  no changes found
  1 local changesets published
  Subject: changeset published
  From: [e-mail]
  In-reply-to: <hg.[e-mail]>
  Message-Id: <hg.[e-mail]>
  Date: * (glob)
  To: [e-mail]
  
  This draft changeset has been published.