Rework of the 'stg pull' policy.
This patch changes the way "stg pull" behaviour is selected, by
replacing stgit.pull-does-rebase and stgit.pullcmd with
stgit.pull-policy, stgit.pullcmd and stgit.fetchcmd. In the standard
case, only pull-policy needs to be set.
Those 3 config variables are also available per-branch as
branch.*.stgit.<name>.
This patch also add a set of tests for the fetch-rebase policy,
including interferences with "stg commit" occuring with 0.12.
Signed-off-by: Yann Dirson <ydirson@altern.org>
~mdw / stgit / commit