status: prefer relative paths in Rust code
… when the repository root is under the current directory,
so the kernel needs to traverse fewer directory in every call
to `read_dir` or `symlink_metadata`.
Better yet would be to use libc functions like `openat` and `fstatat`
to remove such repeated traversals entirely, but the standard library
does not provide APIs based on those.
Maybe with a crate like https://crates.io/crates/openat instead?
Benchmarks of `rhg status` show that this patch is neutral in some configurations,
and makes the command up to ~20% faster in others.
Below is semi-arbitrary subset of results. The four numeric columns are:
time (in seconds) with this changeset’s parent, time with this changeset,
time difference (negative is better), time ratio (less than 1 is better).
```
mercurial-dirstate-v1 | default-plain-clean.no-iu.pbr | 0.0061 -> 0.0059: -0.0002 (0.97)
mercurial-dirstate-v2 | default-plain-clean.no-iu.pbr | 0.0029 -> 0.0028: -0.0001 (0.97)
mozilla-dirstate-v1 | default-plain-clean.no-iu.pbr | 0.2110 -> 0.2102: -0.0007 (1.00)
mozilla-dirstate-v2 | default-copies-clean.ignored.pbr | 0.0489 -> 0.0401: -0.0088 (0.82)
mozilla-dirstate-v2 | default-copies-clean.no-iu.pbr | 0.0479 -> 0.0393: -0.0085 (0.82)
mozilla-dirstate-v2 | default-copies-large.all.pbr | 0.1262 -> 0.1210: -0.0051 (0.96)
mozilla-dirstate-v2 | default-copies-small.ignored-unknown.pbr | 0.1262 -> 0.1200: -0.0062 (0.95)
mozilla-dirstate-v2 | default-copies-small.ignored.pbr | 0.0536 -> 0.0417: -0.0119 (0.78)
mozilla-dirstate-v2 | default-copies-small.no-iu.pbr | 0.0482 -> 0.0393: -0.0089 (0.81)
mozilla-dirstate-v2 | default-plain-clean.ignored.pbr | 0.0518 -> 0.0402: -0.0116 (0.78)
mozilla-dirstate-v2 | default-plain-clean.no-iu.pbr | 0.0481 -> 0.0392: -0.0088 (0.82)
mozilla-dirstate-v2 | default-plain-large.all.pbr | 0.1271 -> 0.1218: -0.0052 (0.96)
mozilla-dirstate-v2 | default-plain-small.ignored-unknown.pbr | 0.1225 -> 0.1202: -0.0022 (0.98)
mozilla-dirstate-v2 | default-plain-small.ignored.pbr | 0.0510 -> 0.0418: -0.0092 (0.82)
mozilla-dirstate-v2 | default-plain-small.no-iu.pbr | 0.0480 -> 0.0394: -0.0086 (0.82)
netbeans-dirstate-v1 | default-plain-clean.no-iu.pbr | 0.1442 -> 0.1422: -0.0020 (0.99)
netbeans-dirstate-v2 | default-plain-clean.no-iu.pbr | 0.0325 -> 0.0282: -0.0043 (0.87)
```
Differential Revision: https://phab.mercurial-scm.org/D12175
test parents command
$ hg init repo
$ cd repo
no working directory
$ hg parents
$ echo a > a
$ echo b > b
$ hg ci -Amab -d '0 0'
adding a
adding b
$ echo a >> a
$ hg ci -Ama -d '1 0'
$ echo b >> b
$ hg ci -Amb -d '2 0'
$ echo c > c
$ hg ci -Amc -d '3 0'
adding c
$ hg up -C 1
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo d > c
$ hg ci -Amc2 -d '4 0'
adding c
created new head
$ hg up -C 3
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg parents
changeset: 3:02d851b7e549
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: c
$ hg parents a
changeset: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: a
hg parents c, single revision
$ hg parents c
changeset: 3:02d851b7e549
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: c
$ hg parents -r 3 c
abort: 'c' not found in manifest
[10]
$ hg parents -r 2
changeset: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: a
$ hg parents -r 2 a
changeset: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: a
$ hg parents -r 2 ../a
abort: ../a not under root '$TESTTMP/repo'
[255]
cd dir; hg parents -r 2 ../a
$ mkdir dir
$ cd dir
$ hg parents -r 2 ../a
changeset: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: a
$ hg parents -r 2 path:a
changeset: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:01 1970 +0000
summary: a
$ cd ..
$ hg parents -r 2 glob:a
abort: can only specify an explicit filename
[10]
merge working dir with 2 parents, hg parents c
$ HGMERGE=true hg merge
merging c
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg parents c
changeset: 3:02d851b7e549
user: test
date: Thu Jan 01 00:00:03 1970 +0000
summary: c
changeset: 4:48cee28d4b4e
tag: tip
parent: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:04 1970 +0000
summary: c2
merge working dir with 1 parent, hg parents
$ hg up -C 2
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ HGMERGE=true hg merge -r 4
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg parents
changeset: 2:6cfac479f009
user: test
date: Thu Jan 01 00:00:02 1970 +0000
summary: b
changeset: 4:48cee28d4b4e
tag: tip
parent: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:04 1970 +0000
summary: c2
merge working dir with 1 parent, hg parents c
$ hg parents c
changeset: 4:48cee28d4b4e
tag: tip
parent: 1:d786049f033a
user: test
date: Thu Jan 01 00:00:04 1970 +0000
summary: c2
$ cd ..