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 >> $HGRCPATH << EOF
> [extensions]
> fastannotate=
> [fastannotate]
> perfhack=1
> EOF
$ hg init repo
$ cd repo
a simple merge case
$ echo 1 > a
$ hg commit -qAm 'append 1'
$ echo 2 >> a
$ hg commit -m 'append 2'
$ echo 3 >> a
$ hg commit -m 'append 3'
$ hg up 1 -q
$ cat > a << EOF
> 0
> 1
> 2
> EOF
$ hg commit -qm 'insert 0'
$ hg merge 2 -q
$ echo 4 >> a
$ hg commit -m merge
$ hg log -G -T '{rev}: {desc}'
@ 4: merge
|\
| o 3: insert 0
| |
o | 2: append 3
|/
o 1: append 2
|
o 0: append 1
$ hg fastannotate a
3: 0
0: 1
1: 2
2: 3
4: 4
$ hg fastannotate -r 0 a
0: 1
$ hg fastannotate -r 1 a
0: 1
1: 2
$ hg fastannotate -udnclf a
test 3 d641cb51f61e Thu Jan 01 00:00:00 1970 +0000 a:1: 0
test 0 4994017376d3 Thu Jan 01 00:00:00 1970 +0000 a:1: 1
test 1 e940cb6d9a06 Thu Jan 01 00:00:00 1970 +0000 a:2: 2
test 2 26162a884ba6 Thu Jan 01 00:00:00 1970 +0000 a:3: 3
test 4 3ad7bcd2815f Thu Jan 01 00:00:00 1970 +0000 a:5: 4
$ hg fastannotate --linear a
3: 0
0: 1
1: 2
4: 3
4: 4
incrementally updating
$ hg fastannotate -r 0 a --debug
fastannotate: a: using fast path (resolved fctx: True)
0: 1
$ hg fastannotate -r 0 a --debug --rebuild
fastannotate: a: 1 new changesets in the main branch
0: 1
$ hg fastannotate -r 1 a --debug
fastannotate: a: 1 new changesets in the main branch
0: 1
1: 2
$ hg fastannotate -r 3 a --debug
fastannotate: a: 1 new changesets in the main branch
3: 0
0: 1
1: 2
$ hg fastannotate -r 4 a --debug
fastannotate: a: 1 new changesets in the main branch
3: 0
0: 1
1: 2
2: 3
4: 4
$ hg fastannotate -r 1 a --debug
fastannotate: a: using fast path (resolved fctx: True)
0: 1
1: 2
rebuild happens automatically if unable to update
$ hg fastannotate -r 2 a --debug
fastannotate: a: cache broken and deleted
fastannotate: a: 3 new changesets in the main branch
0: 1
1: 2
2: 3
config option "fastannotate.mainbranch"
$ hg fastannotate -r 1 --rebuild --config fastannotate.mainbranch=tip a --debug
fastannotate: a: 4 new changesets in the main branch
0: 1
1: 2
$ hg fastannotate -r 4 a --debug
fastannotate: a: using fast path (resolved fctx: True)
3: 0
0: 1
1: 2
2: 3
4: 4
rename
$ hg mv a b
$ cat > b << EOF
> 0
> 11
> 3
> 44
> EOF
$ hg commit -m b -q
$ hg fastannotate -ncf --long-hash b
3 d641cb51f61e331c44654104301f8154d7865c89 a: 0
5 d44dade239915bc82b91e4556b1257323f8e5824 b: 11
2 26162a884ba60e8c87bf4e0d6bb8efcc6f711a4e a: 3
5 d44dade239915bc82b91e4556b1257323f8e5824 b: 44
$ hg fastannotate -r 26162a884ba60e8c87bf4e0d6bb8efcc6f711a4e a
0: 1
1: 2
2: 3
fastannotate --deleted
$ hg fastannotate --deleted -nf b
3 a: 0
5 b: 11
0 a: -1
1 a: -2
2 a: 3
5 b: 44
4 a: -4
$ hg fastannotate --deleted -r 3 -nf a
3 a: 0
0 a: 1
1 a: 2
file and directories with ".l", ".m" suffixes
$ cd ..
$ hg init repo2
$ cd repo2
$ mkdir a.l b.m c.lock a.l.hg b.hg
$ for i in a b c d d.l d.m a.l/a b.m/a c.lock/a a.l.hg/a b.hg/a; do
> echo $i > $i
> done
$ hg add . -q
$ hg commit -m init
$ hg fastannotate a.l/a b.m/a c.lock/a a.l.hg/a b.hg/a d.l d.m a b c d
0: a
0: a.l.hg/a
0: a.l/a
0: b
0: b.hg/a
0: b.m/a
0: c
0: c.lock/a
0: d
0: d.l
0: d.m
empty file
$ touch empty
$ hg commit -A empty -m empty
$ hg fastannotate empty