Explicitly use "tip" in revision navigation.
Rationale: the tip revision is a moving target and if somebody wants tip,
it should be delivered.
default = 'changelog'
header = header.tmpl
changelog = changelog.tmpl
changelogentry = changelogentry.tmpl
filelog = filelog.tmpl
filelogentry = filelogentry.tmpl
tags = tags.tmpl
tagentry = tagentry.tmpl