minirst: allow multiple container types for prune
If we have a container of type x.y, then we can preserve it by
keeping x or y.
config: don't read the same config file twice
In some cases some config files would be read twice and shown twice in
showconfig --debug.
templater: fix precedence of --style and --template options
Since
e3eb480a9391, --template option is ignored if --style is specified,
which is wrong according to the doc of show_changeset():
Display format will be the first non-empty hit of:
1. option 'template'
2. option 'style'
...