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)
# topics
Topics are an experiment to see if maybe the workflow defined by git
branches and hg bookmarks is only partially what users want - perhaps
something that feels more like a traditional VCS branch is right, but
that it should "dissolve" upon being finished. This extension exists
to be a sandbox for that experimentation.
# usage
Enable topics like any mercurial extension: download the source code to a
local directory, and add that directory to your `.hgrc`:
[extensions]
topics=path/to/hg-topics/src