topic: use self instead of repo in topicrepo methods Referring to repo here was somehow preventing it from being garbage-collected (important in hgweb, where currently every request gets a new repo).

evolvecmd: introduce fn to be wrapped by extensions resolving content-div The function added will be used by extension by wrapping it and adding logic to merge data introduced by them. For example: topic extension can wrap this function and add logic to merge topic names.