encoding: fix trim() to be O(n) instead of O(n^2)
`encoding.trim()` iterated over the possible lengths smaller than the
input and created a slice for each. It then calculated the column
width of the result, which is of course O(n), so the overall algorithm
was O(n). This patch rewrites it to iterate over the unicode
characters, keeping track of the length so far. Also, the old
algorithm started from the end of the string, which made it much worse
when the input is large and the limit is small (such as the typical 72
we pass to it).
You can time it by running something like this:
```
time python3 -c 'from mercurial.utils import stringutil; print(stringutil.ellipsis(b"0123456789" * 1000, 5))'
```
That drops from 4.05 s to 83 ms with this patch (and most of that is
of course startup time).
Differential Revision: https://phab.mercurial-scm.org/D12089
#require execbit
Create extension that can disable exec checks:
$ cat > noexec.py <<EOF
> from mercurial import extensions, util
> def setflags(orig, f, l, x):
> pass
> def checkexec(orig, path):
> return False
> def extsetup(ui):
> extensions.wrapfunction(util, 'setflags', setflags)
> extensions.wrapfunction(util, 'checkexec', checkexec)
> EOF
$ hg init unix-repo
$ cd unix-repo
$ touch a
$ hg add a
$ hg commit -m 'unix: add a'
$ hg clone . ../win-repo
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ chmod +x a
$ hg commit -m 'unix: chmod a'
$ hg manifest -v
755 * a
$ cd ../win-repo
$ touch b
$ hg add b
$ hg commit -m 'win: add b'
$ hg manifest -v
644 a
644 b
$ hg pull
pulling from $TESTTMP/unix-repo
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
new changesets 2d8bcf2dda39
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg manifest -v -r tip
755 * a
Simulate a Windows merge:
$ hg --config extensions.n=$TESTTMP/noexec.py merge --debug
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: a03b0deabf2b, local: d6fa54f68ae1+, remote: 2d8bcf2dda39
a: update permissions -> e
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
Simulate a Windows commit:
$ hg --config extensions.n=$TESTTMP/noexec.py commit -m 'win: merge'
$ hg manifest -v
755 * a
644 b
$ cd ..