[PATCH 0/3] add push --current and remote.*.pushHeadOnly

This second series is gets rid of the most annoying part
(IMHO) of push.default = tracking, i.e. the fact that its
behavior cannot be achieved using git's ordinary tools.
While autosetuppush is enough to set the refspecs correctly,
push.tracking does not push _all_ tracked branches, but
only the current one (because it implicitly adds only
one refspec, while autosetuppush places them all in the
configuration).

What I introduce here is "git push --current" and a companion
remote.*.pushHeadOnly option to make it the default.  The
difference between "git push HEAD" and "git push --current"
is that the latter will still walk the remote.*.push refspecs,
but honor only the one matching HEAD.

Together with autosetuppush, this more or less achieves the
same result as push.tracking, at least for newly created
remotes.  A subsequent series will handle the transition.

v2 integrates changes from Nanako's review.  Patch 1 is new
and partially reverts bba0fd2 (push: do not give big warning
when no preference is configured, 2009-07-18).  Patch 2 is the
meat of the implementation.  Most of it actually touches the
transport mechanism, not builtin-push.c (which covers only
one detail about how to handle "git push --current" when
the remote does not have a corresponding push refspec).
Patch 3 adds remote.*.pushHeadOnly.

Paolo Bonzini (3):
      reintroduce PUSH_DEFAULT_UNSPECIFIED
      push: add --current
      push: add remote.*.pushHeadOnly configuration

 Documentation/config.txt   |    6 ++++
 Documentation/git-push.txt |   18 +++++++++++-
 builtin-push.c             |   17 +++++++++--
 cache.h                    |    1 +
 environment.c              |    2 +-
 http-push.c                |   27 ++++++++++++++----
 remote.c                   |   42 ++++++++++++++++++++++++-----
 remote.h                   |    3 ++
 t/t5516-fetch-push.sh      |   64 ++++++++++++++++++++++++++++++++++++++++++++
 transport.c                |   22 ++++++++++++++-
 transport.h                |    1 +
 11 files changed, 183 insertions(+), 20 deletions(-)