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
$ . "$TESTDIR/narrow-library.sh"
create full repo
$ hg init master
$ cd master
$ mkdir inside
$ echo inside > inside/f1
$ mkdir outside
$ echo outside > outside/f2
$ hg ci -Aqm 'initial'
$ hg mv outside/f2 inside/f2
$ hg ci -qm 'move f2 from outside'
$ echo modified > inside/f2
$ hg ci -qm 'modify inside/f2'
$ mkdir outside
$ echo new > outside/f3
$ hg ci -Aqm 'add outside/f3'
$ cd ..
$ hg clone --narrow ssh://user@dummy/master narrow --include inside -r 2
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 2 files
new changesets *:* (glob)
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd narrow
$ hg co 'desc("move f2")'
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg status
$ hg diff
$ hg diff --change . --git
diff --git a/inside/f2 b/inside/f2
new file mode 100644
--- /dev/null
+++ b/inside/f2
@@ -0,0 +1,1 @@
+outside
$ hg log --follow inside/f2 -r tip
changeset: 2:bcfb756e0ca9
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: modify inside/f2
changeset: 1:5a016133b2bb
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: move f2 from outside
$ echo new > inside/f4
$ hg ci -Aqm 'add inside/f4'
$ hg pull -q
$ hg --config extensions.rebase= rebase -d tip
rebasing 3:4f84b666728c "add inside/f4"
saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/4f84b666728c-4269b76e-rebase.hg
$ hg co -q 0
$ echo modified > inside/f1
$ hg ci -qm 'modify inside/f1'
$ echo new > inside/f5
$ hg ci -Aqm 'add inside/f5'
$ hg --config extensions.rebase= rebase -d 'public()' -r .
rebasing 6:610b60178c28 tip "add inside/f5"
saved backup bundle to $TESTTMP/narrow/.hg/strip-backup/610b60178c28-65716a78-rebase.hg