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
====================================
Testing head checking code: Case C-3
====================================
Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.
This case is part of a series of tests checking this behavior.
Category C: case were the branch is only partially obsoleted
TestCase 3: 2 changeset branch, only the head is pruned
.. old-state:
..
.. * 2 changeset branch
..
.. new-state:
..
.. * old head is pruned
.. * 1 new unrelated branch
..
.. expected-result:
..
.. * push denied
..
.. graph-summary:
..
.. B ⊗
.. |
.. A ◔ ◔ C
.. |/
.. ●
$ . $TESTDIR/testlib/push-checkheads-util.sh
Test setup
----------
$ mkdir C3
$ cd C3
$ setuprepos
creating basic server and client repo
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd server
$ mkcommit B0
$ cd ../client
$ hg pull
pulling from $TESTTMP/C3/server
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets d73caddc5533 (1 drafts)
(run 'hg update' to get a working copy)
$ hg up 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mkcommit C0
created new head
$ hg debugobsolete --record-parents `getid "desc(B0)"`
1 new obsolescence markers
obsoleted 1 changesets
$ hg log -G --hidden
@ 0f88766e02d6 (draft): C0
|
| x d73caddc5533 (draft): B0
| |
| o 8aaa48160adc (draft): A0
|/
o 1e4be0697311 (public): root
Actual testing
--------------
$ hg push
pushing to $TESTTMP/C3/server
searching for changes
abort: push creates new remote head 0f88766e02d6
(merge or see 'hg help push' for details about pushing new heads)
[20]
$ cd ../..