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.
Checking how hg behaves when one side of a pull/push doesn't support
some capability (because it's running an older hg version, usually).
$ hg init repo1
$ cd repo1
$ echo a > a; hg add -q a; hg commit -q -m a
$ hg bookmark a
$ hg clone -q . ../repo2
$ cd ../repo2
$ touch $TESTTMP/disable-lookup.py
$ disable_cap() {
> rm -f $TESTTMP/disable-lookup.pyc # pyc caching is buggy
> cat <<EOF > $TESTTMP/disable-lookup.py
> from mercurial import extensions, wireprotov1server
> def wcapabilities(orig, *args, **kwargs):
> cap = orig(*args, **kwargs)
> cap.remove(b'$1')
> return cap
> extensions.wrapfunction(wireprotov1server, '_capabilities', wcapabilities)
> EOF
> }
$ cat >> ../repo1/.hg/hgrc <<EOF
> [extensions]
> disable-lookup = $TESTTMP/disable-lookup.py
> EOF
$ hg pull ssh://user@dummy/repo1 -r tip -B a
pulling from ssh://user@dummy/repo1
no changes found
$ disable_cap lookup
$ hg pull ssh://user@dummy/repo1 -r tip -B a
pulling from ssh://user@dummy/repo1
abort: other repository doesn't support revision lookup, so a rev cannot be specified.
[255]
$ disable_cap pushkey
$ hg pull ssh://user@dummy/repo1 -r tip -B a
pulling from ssh://user@dummy/repo1
abort: remote bookmark a not found!
[10]