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
# same user, same group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# same user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, same group
not trusting file .hg/hgrc from untrusted user abc, group bar
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, same group, but we trust the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group, but we trust the user
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group, but we trust the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# different user, different group, but we trust the user and the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we trust all users
# different user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we trust all groups
# different user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we trust all users and groups
# different user, different group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# we don't get confused by users and groups with the same name
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# list of user names
# different user, different group, but we trust the user
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# list of group names
# different user, different group, but we trust the group
trusted
global = /some/path
local = /another/path
untrusted
. . global = /some/path
. . local = /another/path
# Can't figure out the name of the user running this process
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# prints debug warnings
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
ignoring untrusted configuration option paths.local = /another/path
global = /some/path
untrusted
. . global = /some/path
. ignoring untrusted configuration option paths.local = /another/path
. local = /another/path
# report_untrusted enabled without debug hides warnings
# different user, different group
trusted
global = /some/path
untrusted
. . global = /some/path
. . local = /another/path
# report_untrusted enabled with debug shows warnings
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
trusted
ignoring untrusted configuration option paths.local = /another/path
global = /some/path
untrusted
. . global = /some/path
. ignoring untrusted configuration option paths.local = /another/path
. local = /another/path
# ui.readconfig sections
quux
# read trusted, untrusted, new ui, trusted
not trusting file foobar from untrusted user abc, group def
trusted:
ignoring untrusted configuration option foobar.baz = quux
None
untrusted:
quux
# error handling
# file doesn't exist
# same user, same group
# different user, different group
# parse error
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
ignored .hg/hgrc:1: foo
# same user, same group
config error at .hg/hgrc:1: foo
# access typed information
# different user, different group
not trusting file .hg/hgrc from untrusted user abc, group def
# suboptions, trusted and untrusted
(None, []) ('main', [('one', 'one'), ('two', 'two')])
# path, trusted and untrusted
None .hg/monty/python
# bool, trusted and untrusted
False True
# int, trusted and untrusted
0 42
# bytes, trusted and untrusted
0 84934656
# list, trusted and untrusted
[] ['spam', 'ham', 'eggs']