Update on the topic experiment

[Pierre-Yves David]

Good new everyone, some advance on the topic experiment front,

I manage to take some time during the last few days to bring a new set
of feature/behavior to this experiment. The whole things is very hacky
but it should give us a good idea of where this could be going. The UI
is quite rough but that was not really the initial focus. Evolve have
also been updated to collaborate more closely with topic too. This is
at "proof of concept" stage and already contains various known bugs.
For example, all commit will issue the "create a new head" warning.

By some miracle, this is compatible with both Mercurial 3.7 and the
current tip of default. But future iteration version will likely be
compatible with the tip of default only (future 3.8)

The code can be find here: http://hg.netv6.net/topic

We'll try to publish an official numbered version (for both topic and
evolve) shortly.

Here is quick run down on topic features and behaviors:

What existed before this iteration?
-----------------------------------

  - "hg topic NAME" activates a topic to be used for all subsequent
    commits,

  - "hg topic" lists all existing topics (and flag the active one)

  - "hg up NAME" brings you to the tip most changeset in the topic (and
     activate the topic)

  - The "topic(NAME)" revset selects all changesets on a topic.


What's new?
-----------

  - "hg up BRANCHNAME" now brings you to the tipmost changeset of a
    branch with no attached topic. (same for hg log BRANCHNAME, etc)

  - When you have no active topic:

    - bare "hg update" will bring you to the tipmost changeset (on the
      same branch) with no topic.

    - bare "hg update" will not warn about other heads with a topic.

    - default merge and rebase destination will ignore heads with a
      topic.

  - If you have an active topic.

    - bare "hg update" will bring you to the tipmost change with this
      topic,

    - default merge and rebase destination will be first other head
      topic, then head of the current branch without a topic,

    - default histedit destination will not go further than your
      current topic.

  - "hg push" to a non-publishing server (with topic support) will not
    requires --force to push new head with a topic (As long as you
    stick to one head per topic.

  - "hg topic --list" will give you compact list of all changesets in
    your topic. This is close to 'hg log -r topic(.)' would do, but it
    filter out obsolete one and make sure they are displayed in the
    right other even in the unstability case. The list highlight the
    current working copy parent and show what part of the stack is
    unstable.

    - Index of changeset in "hg topic --list" can be use to refer to
      changeset in the current topic. "hg up t2" will bring you to the
      3rd changeset in the stack (3rd, because of lazyness and zero
      indexing).

    - The changeset in that command can be retrieved using using the
      "stack()" revset. The special ordering is preserved.

What happened on the evolve front?
----------------------------------

  - "hg evolve" now properly preserves topic of the source changesets.

  - If you have an active topic "hg evolve --all" will select all
    changesets in the topic for resolution.

  - "hg prev" and "hg next" will stay within the active topic by
    default.

Happy testing.

-- 
Pierre-Yves David