[PATCH v4 00/28] First class shallow clone

This reroll should fix all comments I have received in v3. I reordered the shallow checks a bit so in common case it should be as cheap as a normal fetch or push. See 08/28 and 20/28 for the big picture. I'm not entirely happy with the hook issue in 20/28, but it looks good enough for me. There are a few XXXes for further improvement, but I'll keep them until this lands.

To recap, this series allows you to clone from a shallow repo, push to or fetch from any shallow repo. Normally it will reject new refs that introduce new shallow boundaries to your repository, so if you're in a full clone, it will always stay a full clone. Use "fetch --update-shallow" or set receive.shallowupdate to accept those refs.

Nguyễn Thái Ngọc Duy (28):
  transport.h: remove send_pack prototype, already defined in send-pack.h
  Replace struct extra_have_objects with struct sha1_array
  send-pack: forbid pushing from a shallow repository
  clone: prevent --reference to a shallow repository
  Make the sender advertise shallow commits to the receiver
  connect.c: teach get_remote_heads to parse "shallow" lines
  shallow.c: extend setup_*_shallow() to accept extra shallow commits
  shallow.c: the 8 steps to select new commits for .git/shallow
  shallow.c: steps 6 and 7 to select new commits for .git/shallow
  fetch-pack.c: move shallow update code out of fetch_pack()
  fetch-pack.h: one statement per bitfield declaration
  clone: support remote shallow repository
  fetch: support fetching from a shallow repository
  upload-pack: make sure deepening preserves shallow roots
  fetch: add --update-shallow to accept refs that update .git/shallow
  receive-pack: reorder some code in unpack()
  receive/send-pack: support pushing from a shallow clone
  New var GIT_SHALLOW_FILE to propagate --shallow-file to subprocesses
  connected.c: add new variant that runs with --shallow-file
  receive-pack: allow pushes that update .git/shallow
  send-pack: support pushing to a shallow clone
  remote-curl: pass ref SHA-1 to fetch-pack as well
  Support shallow fetch/clone over smart-http
  receive-pack: support pushing to a shallow clone via http
  send-pack: support pushing from a shallow clone via http
  clone: use git protocol for cloning shallow repo locally
  prune: clean .git/shallow after pruning objects
  git-clone.txt: remove shallow clone limitations

 Documentation/config.txt                  |   4 +
 Documentation/fetch-options.txt           |  14 +-
 Documentation/git-clone.txt               |   7 +-
 Documentation/git-prune.txt               |   2 +
 Documentation/gitremote-helpers.txt       |   7 +
 Documentation/technical/pack-protocol.txt |   7 +-
 builtin/clone.c                           |  18 +-
 builtin/fetch-pack.c                      |  23 +-
 builtin/fetch.c                           |  15 +-
 builtin/gc.c                              |   1 +
 builtin/prune.c                           |   4 +
 builtin/receive-pack.c                    | 314 +++++++++++++++----
 builtin/send-pack.c                       |   9 +-
 cache.h                                   |   3 +
 commit.h                                  |  39 ++-
 connect.c                                 |  22 +-
 connected.c                               |  42 ++-
 connected.h                               |   2 +
 environment.c                             |   6 +
 fetch-pack.c                              | 132 +++++++-
 fetch-pack.h                              |  29 +-
 git.c                                     |   2 +-
 remote-curl.c                             |  34 ++-
 remote.h                                  |   9 +-
 send-pack.c                               |  27 +-
 send-pack.h                               |   2 +-
 shallow.c                                 | 486 +++++++++++++++++++++++++++++-
 t/t5304-prune.sh                          |  10 +
 t/t5536-fetch-shallow.sh (new +x)         | 203 +++++++++++++
 t/t5537-push-shallow.sh (new +x)          | 183 +++++++++++
 t/t5601-clone.sh                          |   7 +
 trace.c                                   |   2 +-
 transport-helper.c                        |   6 +
 transport.c                               |  25 +-
 transport.h                               |  16 +-
 upload-pack.c                             |   8 +-
 36 files changed, 1555 insertions(+), 165 deletions(-)
 create mode 100755 t/t5536-fetch-shallow.sh
 create mode 100755 t/t5537-push-shallow.sh