tests/test-gendoc-it.t

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.

#require docutils gettext

  $ $TESTDIR/check-gendoc it
  checking for parse errors