[DRE-maint] git-buildpackage workflow

[Jérémy Lal]

Hi,
i want to switch to a simpler and more efficient way
of using gbp branches for the packages i am maintaining :

* always import on "upstream" branch
* work on latest versions is made on "master" branch
* create branches of "master" when needed, but use them
  only for bug fixing (typically: "master-wheezy")

No more master-experimental, upstream-experimental couples
i carelessly setup couple of years ago, and that don't
follow how git branches are supposed to be used.

For this to work gbp must have this option :
pristine-tar = True

Also to avoid having to update debian/gbp.conf for each
branch of master, i'd like to use this option :
ignore-branch = True

gbp will (by default) find correct tags on upstream branch,
and whatever the developer is doing, he's supposed to be
on the right debian branch, so just ignore it.

If you are concerned by those packages (mainly redmine, nodejs,
libv8, npm, because others didn't have experimental branches),
please add your comments.

Jérémy.