Add persistent-https to contrib

Git over HTTPS has a high request startup latency, since the SSL
negotiation can take up to a second. In order to reduce this latency,
connections should be left open to the Git server across requests
(or invocations of the git commandline).

Reduce SSL startup latency by running a daemon job that keeps
connections open to a Git server. The daemon job
(git-remote-persistent-https--proxy) is started on the first request
through the client binary (git-remote-persistent-https) and remains
running for 24 hours after the last request, or until a new daemon
binary is placed in the PATH. The client determines the daemon's
HTTP address by communicating over a UNIX socket with the daemon.
From there, the rest of the Git protocol work is delegated to the
"git-remote-http" binary, with the environment's http_proxy set to
the daemon.

Accessing /pub/scm/linux/kernel/git/torvalds/linux repository hosted
at kernel.googlesource.com with "git ls-remote" over https:// and
persistent-https:// 5 times shows that the first request takes about
the same time (0.193s vs 0.208s---there is a slight set-up cost for
the local proxy); as expected, the other four requests are much
faster (~0.18s vs ~0.08s).

Incidentally, this also has the benefit of HTTP keep-alive working
across Git command invocations. Its common for servers to use a 5
minute keep-alive on an HTTP 1.1 connection. Git-over-HTTP commonly
uses Transfer-Encoding: chunked on replies, so keep-alive will
generally just work, even though a pack stream's length isn't known
in advance. Because the helper is an external process holding that
connection open, we also benefit from being able to reuse an
existing TCP connection to the server.  The same "git ls-remote"
test against http:// vs persistent-https:// URL shows that the
former takes ~0.09s while the first request for the latter is about
0.134s with set-up cost, and subsequent requests are ~0.065s,
shaving around one RTT to the server.

Signed-off-by: Colby Ranger <cranger@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'master' into next

By Jiang Xin (5) and others
via Junio C Hamano (15) and Jiang Xin (1)
* master:
  Update draft release notes to 1.7.11
  Start preparing for 1.7.10.4
  i18n: apply: split to fix a partial i18n message
  l10n: Set nplurals of zh_CN.po from 1 to 2
  l10n: zh_CN.po: translate 323 new messages
  l10n: zh.CN.po: update by msgmerge git.pot
  First release translation for Vietnamese
  Init translation for Vietnamese
  l10n: New it.po file with 504 translations
  Update Swedish translation (728t0f0u)
  l10n: Update git.pot (41 new messages)
Merge branch 'cr/persistent-https' into next

A remote helper that acts as a proxy that caches ssl session for the
https:// transport is added to the contrib/ area.

By Colby Ranger
* cr/persistent-https:
  Add persistent-https to contrib
Sync with 1.7.11-rc1

* master:
  Git 1.7.11-rc1
  Git 1.7.10.4
Merge branch 'jk/blame-tree' into HEAD

* jk/blame-tree:
  blame-tree wip
Merge branch 'jk/builtin-attr' into HEAD

* jk/builtin-attr:
  attr: drop C/C++ default extension mapping
  attr: map builtin userdiff drivers to well-known extensions
Merge branch 'jk/bundle-fetch' into HEAD

* jk/bundle-fetch:
  clone: give advice on how to resume a failed clone
  remote-curl: resume interrupted bundle transfers
  remote-curl: show progress for bundle downloads
  progress: allow pure-throughput progress meters
  remote-curl: try base $URL after $URL/info/refs
  remote-curl: auto-detect bundles when fetching refs
  remote-curl: free "discovery" object
  bundle: add is_bundle_buf helper
  transport: factor out bundle to ref list conversion
  remote-curl: use http callback for requesting refs
  http: add a public function for arbitrary-callback request
  http: refactor http_request function
  http: turn off curl signals
  t/lib-httpd: check for NO_CURL
Merge branch 'jk/cache-patch-id' into HEAD

* jk/cache-patch-id:
  cache patch ids on disk
  cherry: read default config
  implement metadata cache subsystem
  map: implement persistent maps
  decorate: use "map" for the underlying implementation
  fast-export: use object to uint32 map instead of "decorate"
  implement generic key/value map
Merge branch 'jk/child-cleanup' into HEAD

* jk/child-cleanup:
  send-pack: kill pack-objects helper on signal or exit
Merge branch 'jk/clone-file-local' into HEAD

* jk/clone-file-local:
  clone: send diagnostic messages to stderr
  clone: allow --no-local to turn off local optimizations
  docs/clone: mention that --local may be ignored
Merge branch 'jk/config-sources' into HEAD

* jk/config-sources:
  show sources of config options (WIP)
Merge branch 'jk/describe' into HEAD

* jk/describe:
  describe WIP
Merge branch 'jk/dumpstat' into HEAD

* jk/dumpstat:
  zeromq dumpstat implementation
  dumpstat-ify upload-pack
  dumpstat to fd
  dumpstat
Merge branch 'jk/external-odb' into HEAD

* jk/external-odb:
  fetch-pack: advertise external odb blobs
  external odb foreach
  external odb work in progress
Merge branch 'jk/fast-commit-list' into HEAD

* jk/fast-commit-list:
  fetch-pack: use priority queue for mark_complete
  commit: add infrastructure for priority queues of commits
  basic priority queue implementation
Merge branch 'jk/fetch-tracking' into HEAD

* jk/fetch-tracking:
  fetch tracking wip
Merge branch 'jk/filter-branch-example' into HEAD

* jk/filter-branch-example:
  docs/filter-branch: clean up newsubdir example
  update-index: add --clear option
Merge branch 'jk/generations' into HEAD

* jk/generations:
  limit "contains" traversals based on commit generation
  check commit generation cache validity against grafts
  pretty: support %G to show the generation number of a commit
  commit: add commit_generation function

Conflicts:
	metadata-cache.c
	metadata-cache.h
Merge branch 'jk/ignore-have' into HEAD

* jk/ignore-have:
  receive-pack: respect receive.advertiseAlternates config
Merge branch 'jk/leading-symlinks' into HEAD

* jk/leading-symlinks:
  don't cross submodule boundaries in add