push: rework the computation of fallbackheads to be correct
The previous computation tried to be smart but ended up being wrong. This was
caught by phase movement test while reworking the phase discovery logic to be
faster.
The previous logic was failing to catch case where the pushed set was not based
on a common heads (i.e. when the discovery seemed to have "over discovered"
content, outside the pushed set)
In the following graph, `e` is a common head and we `hg push -r f`. We need to
detect `c` as a fallback heads and we previous failed to do so::
e
|
d f
|/
c
|
b
|
a
The performance impact of the change seems minimal. On the most impacted
repository at hand (mozilla-try), the slowdown seems mostly mixed in the
overall noise `hg push` but seems to be in the hundred of milliseconds order of
magnitude. When using rust, we seems to be a bit faster, probably because we
leverage more accelaratd internals.
I added a couple of performance related common for further investigation later
on.
#require symlink
Create extension that can disable symlink support:
$ cat > nolink.py <<EOF
> from mercurial import extensions, util
> def setflags(orig, f, l, x):
> pass
> def checklink(orig, path):
> return False
> def extsetup(ui):
> extensions.wrapfunction(util, 'setflags', setflags)
> extensions.wrapfunction(util, 'checklink', checklink)
> EOF
$ hg init unix-repo
$ cd unix-repo
$ echo foo > a
$ ln -s a b
$ hg ci -Am0
adding a
adding b
$ cd ..
Simulate a checkout shared on NFS/Samba:
$ hg clone -q unix-repo shared
$ cd shared
$ rm b
$ echo foo > b
$ hg --config extensions.n=$TESTTMP/nolink.py status --debug
ignoring suspect symlink placeholder "b"
Make a clone using placeholders:
$ hg --config extensions.n=$TESTTMP/nolink.py clone . ../win-repo
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd ../win-repo
$ cat b
a (no-eol)
$ hg --config extensions.n=$TESTTMP/nolink.py st --debug
Empty placeholder:
$ rm b
$ touch b
$ hg --config extensions.n=$TESTTMP/nolink.py st --debug
ignoring suspect symlink placeholder "b"
Write binary data to the placeholder:
>>> open('b', 'w').write('this is a binary\0') and None
$ hg --config extensions.n=$TESTTMP/nolink.py st --debug
ignoring suspect symlink placeholder "b"
Write a long string to the placeholder:
>>> open('b', 'w').write('this' * 1000) and None
$ hg --config extensions.n=$TESTTMP/nolink.py st --debug
ignoring suspect symlink placeholder "b"
Commit shouldn't succeed:
$ hg --config extensions.n=$TESTTMP/nolink.py ci -m1
nothing changed
[1]
Write a valid string to the placeholder:
>>> open('b', 'w').write('this') and None
$ hg --config extensions.n=$TESTTMP/nolink.py st --debug
M b
$ hg --config extensions.n=$TESTTMP/nolink.py ci -m1
$ hg manifest tip --verbose
644 a
644 @ b
$ cd ..