[PATCH 0/8] Resumable clone revisited, proof of concept

I was reminded by LWN [1] about this. Annoyed in fact because it's called a bug while it looks more like an elephant. So let's see if we can agree this is a good way to go.

This is the stable pack approach. The client initiates "resumable mode" and forces the server to generate a resumable, even though less efficient, pack. Compared to the "download from a cached bundle first" approach, this requires no extra setup for caching. But it wastes more cpu.

The UI is not there yet, and you can only resume a fetch, not a clone. What remains to do are:

 - Add UI to "git fetch" to retry
 - Make "git clone" use "git fetch --resume" to get the pack

[1] Quote from https://lwn.net/Articles/674392/ "she noted that Git
    still does not support interrupting and resuming download operations,
    which is an important bug to fix."

Nguyễn Thái Ngọc Duy (8):
  pack-objects: add --skip and --skip-hash
  pack-objects: produce a stable pack when --skip is given
  index-pack: add --append-pack=<path>
  upload-pack: new capability to pass --skip* to pack-objects
  fetch-pack.c: send "skip" line to pack-objects
  fetch: add --resume-pack=<path>
  index-pack: --append-pack implies --strict
  one ugly test to verify basic functionality

 Documentation/technical/pack-protocol.txt         |  2 +
 Documentation/technical/protocol-capabilities.txt |  9 ++++
 builtin/fetch-pack.c                              |  4 ++
 builtin/fetch.c                                   |  5 +++
 builtin/index-pack.c                              | 52 ++++++++++++++++++++++-
 builtin/pack-objects.c                            | 26 ++++++++++++
 csum-file.c                                       | 52 +++++++++++++++++++++--
 csum-file.h                                       |  3 ++
 fetch-pack.c                                      | 40 +++++++++++++++++
 fetch-pack.h                                      |  3 ++
 remote-curl.c                                     |  8 +++-
 t/t5544-fetch-resume.sh (new +x)                  | 42 ++++++++++++++++++
 transport.c                                       |  4 ++
 transport.h                                       |  4 ++
 upload-pack.c                                     | 30 ++++++++++++-
 15 files changed, 275 insertions(+), 9 deletions(-)
 create mode 100755 t/t5544-fetch-resume.sh