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

update: change default update destination to take topic in account When within a branch update to ngtip(branch). When within a topic update to the top topic.

rebase: test default rebase destination behavior In future mercurial 3.8, rebase and merge share the same destination logic. So if merge work, rebase should work as well. However, we double test it to be sure. Especially, in 3.7 the logic is not shared so we have to introduce an extra hack to share it in this case.

topicmap: write and read format from disc To prevent too awful performance we allow writing and reading topicmap cache. This is done with a lot of code duplication from core because core is not extensible enough.