template: add minimal obsfate template function
The goal of this series is to have templates capable of displaying the
evolution of a changeset in a clean and human-readable way.
Add the succsandmarkers template return successors and markers so it can be
used separately like this:
> {succsandmarkers % "{get(succsandmarkers, "markers")|json};"}
The following patches will add template functions that takes successors and
markers as inputs and compute various obsfate fields from them.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state