backout: allow backout of merge changeset with --parent option.
--parent allows to choose which parent of merge to revert to.
default = 'changelog'
header = header-rss.tmpl
changelog = changelog-rss.tmpl
changelogentry = changelogentry-rss.tmpl
filelog = filelog-rss.tmpl
filelogentry = filelogentry-rss.tmpl
tags = tags-rss.tmpl
tagentry = tagentry-rss.tmpl