New @ bookmark on Savannah repo

[Jordi Gutiérrez Hermoso]

tl;dr: Do "hg update @" next time you pull from Savannah and
preferrably use hg version 2.4 or later. When switching branches,
prefer "hg update @" instead of "hg update default".

Explanation follows.

I have just pushed to Savannah a new bookmark called "@". The point is
that since I am recommending our GSoC students to use bookmarks
instead of named branches to track their development, it seems
inconvenient to not have some sort of bookmark for our main changes on
the default branch.

The @ bookmark is a bookmark that gets special treatment since
Mercurial 2.4. The special treatment that it gets is that on new
clones, hg by default updates to the @ bookmark and makes it active.
The active bookmark is the one that gets follows you (advances) when
you make a commit. So when you do "hg update @" and make new commits,
you'll be advancing the @ bookmark. This will help from distinguishing
our heads from students' heads on the default branch.

It's not great tragedy if we forget to advance the "@" bookmark, or if
you're using an older hg version. By their very nature, bookmarks are
rather ephemeral, so we can always advance it later.

Keep calm and carry on,
- Jordi G. H.