[PATCH 0/4] Introduce a "promisor-remote" capability

Earlier this year, I sent 3 versions of a patch series with the goal of allowing a client C to clone from a server S while using the same promisor remote X that S already use. See:

https://lore.kernel.org/git/20240418184043.2900955-1-christian.couder@gmail.com/

Junio suggested to instead implement that feature using:

"a protocol extension that lets S tell C that S wants C to fetch missing objects from X (which means that if C knows about X in its ".git/config" then there is no need for end-user interaction at all), or a protocol extension that C tells S that C is willing to see objects available from X omitted when S does not have them (again, this could be done by looking at ".git/config" at C, but there may be security implications???)"

This patch series implements that protocol extension called "promisor-remote" (that name is open to change or simplification) which allows S and C to agree on C using X directly or not.

I have tried to implement it in a quite generic way that could allow S and C to share more information about promisor remotes and how to use them.

For now C doesn't use the information it gets from S when cloning. That information is only used to decide if C is Ok to use the promisor remotes advertised by S. But this could change which could make it much simpler for clients than using the current way of passing information about X with the `-c` option of `git clone` many times on the command line.

Another improvement could be to not require GIT_NO_LAZY_FETCH=0 when S and C have agreed on using S.

Christian Couder (4):
  version: refactor strbuf_sanitize()
  strbuf: refactor strbuf_trim_trailing_ch()
  Add 'promisor-remote' capability to protocol v2
  promisor-remote: check advertised name or URL

 Documentation/config/promisor.txt     |  18 ++
 Documentation/gitprotocol-v2.txt      |  37 +++++
 connect.c                             |   7 +
 promisor-remote.c                     | 228 ++++++++++++++++++++++++++
 promisor-remote.h                     |  26 ++-
 serve.c                               |  21 +++
 strbuf.c                              |  16 ++
 strbuf.h                              |  10 ++
 t/t5555-http-smart-common.sh          |   1 +
 t/t5701-git-serve.sh                  |   1 +
 t/t5710-promisor-remote-capability.sh | 192 ++++++++++++++++++++++
 trace2/tr2_cfg.c                      |  10 +-
 upload-pack.c                         |   3 +
 version.c                             |   9 +-
 14 files changed, 563 insertions(+), 16 deletions(-)
 create mode 100755 t/t5710-promisor-remote-capability.sh