stack: exclude obsolete changeset from the set We care about relevant changeset, obsolete have a new version somewhere and we don't care about the old one in our display. In case of unstability, the ordering used is still wrong.

stack: add a very first version of stack display with 'hg topic --list' This mark the first step toward a set of feature dedicated to displaying and moving within the current stack of work. Everything is still super basic so don't look too much at the feature. The goals of this changeset are: * having a flag to trigger the feature * having a basic (imperfect selection mechanism)

topic: get 'Abort' from error, not 'util' The class live in 'mercurial.error'.

Makefile: meant tests-@ not tests-tip