branchcache: add a "pure topological head" fast path
In a narrow but actually quick common case, all topological heads are all on
the same branch and all open. In this case, computing the branch map is very
simple. We can quickly detect situation where this situation will not change.
So we update the V3 format to be able to express this situation and upgrade the
update code to detect we remains in that mode.
The branch cache is populated with the actual value when the branch map is
accessed, but the update_disk method can do the update without needing to
populate it.
#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 ..