templates-default: factor out definition of changeset labels
This is redundant for normal and debug mode and prepares extension of this
list that should effect both modes.
cmdutil: add support for evolution "troubles" display in changeset_printer
Add a "trouble" line in changeset header along with a couple of labels on
"log.changeset" line to indicate whether a changeset is troubled or not and
which kind trouble occurs.
cmdutil: extract a _changesetlabels function out of changeset_printer._show()
There is a common logic in changeset_printer and in the summary command for
labelling a changeset.
This prepares extension of changeset's labels with evolution "troubles"
information that would show up in both log and summary outputs. Ultimately,
both would use this function.