revset: add `unstable` alias for `troubled`
Per https://www.mercurial-scm.org/wiki/CEDVocabulary. The old name is still
available (but undocumented) for compatibility. `Orphan` was renamed from
`unstable` in core in 4.4, so this seems safe to do now.
Test that share-clones use the cache in the original repository.
$ . $TESTDIR/testlib/common.sh
$ hg init share-base
$ cd share-base/
$ cat >> .hg/hgrc <<EOF
> [extensions]
> evolve=
> share=
> EOF
$ hg debugbuilddag .+3:branchpoint+4*branchpoint+2
$ cd ..
$ hg --config extensions.share= share -U share-base share-client
$ cd share-client
$ hg debugupdatecache
$ test -d .hg/cache
[1]
$ test -d ../share-base/.hg/cache