[PATCH 0/4 v3] Introducing the .git file

This is a resend of my previous series implementing the .git file, rebased on top of todays master (e3c58f8b). The patches are identical to the final suggestions in http://thread.gmane.org/gmane.comp.version-control.git/74258 except for the previous 1/5 which is dropped from the series (since it already appears in master). There are also some minor touch-ups to the commit messages.

Shortlog:
 Add platform-independent .git "symlink"
 Teach resolve_gitlink_ref() about the .git file
 Teach git-submodule.sh about the .git file
 Teach GIT-VERSION-GEN about the .git file

Diffstat:
 Documentation/repository-layout.txt |    5 ++-
 GIT-VERSION-GEN                     |    2 +-
 cache.h                             |    1 +
 environment.c                       |    2 +
 git-submodule.sh                    |    4 +-
 refs.c                              |   17 +++++-
 setup.c                             |   47 ++++++++++++++++
 t/t0002-gitfile.sh                  |  103 +++++++++++++++++++++++++++++++++++
 8 files changed, 174 insertions(+), 7 deletions(-)