obslog: make changeset available to templater
obslog templating currently has very limited support for templating
the precursor changeset (when available). The only available keywords
are {node}, {rev}, and {shortdescription}. This patch makes the entire
changeset available to the templater by passing it to
formatter.context(). That function has been available since Mercurial
4.2.
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