cleanups in revlog.lookup
- add comments
- do a clean separation of the different cases
- don't use a list of each possible node when
doing the lookup, just keep the previous entry
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