[RFC PATCH 0/8] Git remote helpers to implement smart transports.

This series implements extensions to remote helpers for carrying smary transports. It is against next, because master doesn't contain necressary patches (the allow specifying remote helper in url one).

First patch reworks URL handling so that unknown protocols are passed to remote helpers. This allows having remote helpers implement git transports without duplicating the protocol part.

Second patch refactors git transport option parsing to split smart transport option to own structure and keep this structure up to date with encountered options. This is needed if transport turns out to be smart transport.

Third patch adds capabilty to have git smart transport code take over connection, replacing "layer 7" with git smart transport protocols.

Fourth patch actually adds the extensions to external transport code to allow helpers signal that transport should be taken over (become smart transport).

Fifth patch extends 'git archive' to allow snapshotting off any transport that uses git smart transport code, not just file://, git:// and ssh://

Sixth patch removes special casing of http, https and ftp. And while at it, adds ftps, since CURL supports it.

Seventh patch adds debug mode for remote helpers. Might be useful for debugging deadlocks by showing command traffic between git executable and remote helper.

Eighth patch adds support for remote helper to signal that it requires some capability and have git complain if it doesn't know it.

Misc remarks:

Underlying network link is assumed to be full-duplex since most of the time if the underlying link isn't HTTP, it will be full-duplex (most of the time even TCP).

Simplest deadlock-free buffering is just to read incoming pipe from git when there's no data to send to remote end. This gives adequate performance in all cases except when sending large initial ref adverts (and those are ended by flush anyway, so those can be safely buffered). So no extensions to add missing flushes are needed.

Ilari Liusvaara (8):
  Pass unknown protocols to external protocol handlers
  Refactor git transport options parsing
  Support taking over transports
  Support remote helpers implementing smart transports
  Support remote archive from external protocol helpers
  Remove special casing of http, https and ftp
  Add remote helper debug mode
  Support mandatory capabilities

 .gitignore                           |    5 +-
 Documentation/git-remote-helpers.txt |   35 ++++-
 Makefile                             |   16 ++-
 builtin-archive.c                    |   17 ++-
 transport-helper.c                   |  270 ++++++++++++++++++++++++++++-----
 transport.c                          |  258 ++++++++++++++++++++++++++------
 transport.h                          |   32 ++++
 7 files changed, 533 insertions(+), 100 deletions(-)