Teach UploadPack to take a provider of URIs corresponding to cached
packs. When fetching, if the client supports the packfile-uri feature,
and if such a cached pack were to be streamed, instead send the
corresponding URI.

This packfile-uri feature is implemented in the jt/fetch-cdn-offload
branch of Git. There is interest in this feature [1], but it is not yet
merged.

[1] https://public-inbox.org/git/cover.1552073690.git.jonathantanmy@google.com/

Change-Id: I9a32dae131c9c56ad2ff4a8a9638ae3b5e44dc15
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

Allow the client to specify "sideband-all" in a fetch v2 request,
indicating that the whole response is to be multiplexed (with a sideband
indicator on every non-flush and non-delim pkt) instead of only the
packfile being multiplexed. This allows, for example, progress messages
to be sent at any point in the response.

This implements the "sideband-all" feature documented in
Documentation/technical/protocol-v2.txt in Git.

Change-Id: I3e7f21c88ff0982b1b7ebb09c9ad6c742c4483c8
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

Allows callers to read all lines in the input stream until the
END marker is reached, without having to explicitly check for
the END marker.

Replace all remaining usage of the END marker with the new method.

Change-Id: I51f419c7f569ab7ed01e1aaaf6b40ed8cdc2116b
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Replace reference comparisons of PacketLineIn's DELIM and END strings
with usage of the helper methods isDelimiter() and isEnd().

Change-Id: I52dcfc4ee9097f1bd6970601c716701847d9eebd
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

This increases type-safety and is ground work for support of the
"tree:<depth>" filter.

Change-Id: Id19eacdcdaddb9132064c642f6d554b1060efe9f
Signed-off-by: Matthew DeVore <matvore@gmail.com>

This code is not specific to V2 of the protocol, so it doesn't belong
there. Move it to its own class.

Change-Id: I8084764147d1d0e2bceaaead59b332a8ec1a0825
Signed-off-by: Matthew DeVore <matvore@gmail.com>

ProtocolV2Parser explains:

  // TODO(ifrade): This validation should be done after the
  // protocol parsing. It is not a protocol problem asking for an
  // unexisting ref and we wouldn't need the ref database here.

Do so.  This way all ref database accesses are in one place, in the
UploadPack class.

No user-visible change intended --- this is just to make the code
easier to manipulate.

Change-Id: I68e87dff7b9a63ccc169bd0836e8e8baaf5d1048
Signed-off-by: Jonathan Nieder <jrn@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

In protocol v2, a command request can be followed by server options
(lines like "agent=<>" and "server-option=<>"), but current code
doesn't accept those lines.

Advertise the "server-option" capability, parse the lines and add
them to the request objects.

Other code in JGit can see this options and act accordingly via the
protocol v2 hooks.

This should not require any change in the client side.

Change-Id: If3946390f9cc02d29644b6ca52534b6f757bda9f
Signed-off-by: Ivan Frade <ifrade@google.com>

In FetchV0Request, the fields "wantsIds" and "options" are called
"wantIds" and "clientCapabilities". Those names describe them better.

Rename FetchV2Request fields to follow fetch v0. This will make easier
to extract a superclass later.

Take also the chance to polish the javadoc.

Change-Id: Ia17dbbab8084f39cc529fef9ca5c65e189073767
Signed-off-by: Ivan Frade <ifrade@google.com>

Fetch code has been moved to a ProtocolV2Parser, but ls-refs code is
still in UploadPack.

Moving it to the parser makes it easier to test, keeps the parsing
together and makes the two commands follow similar structure.

Change-Id: I573ce543e804ddeb9f83303b4af250b7cddc8cad
Signed-off-by: Ivan Frade <ifrade@google.com>

The parsing code for protocol v2 fetch doesn't have any dependency on
the rest of UploadPack.

Move it to its own class. This makes testing easier (no need to
instantiate the full UploadPack), simplifies the code in UploadPack and
increases modularity.

At the moment, the parser needs to know about the reference database to
validate incoming references. This dependency could be easily removed
moving the validation later in the flow, after the parsing, where other
validations are already happening. Postponing that to keep this patch
about moving unmodified code around.

Change-Id: I7ad29a6b99caa7c12c06f5a7f30ab6a5f6e44dc7
Signed-off-by: Ivan Frade <ifrade@google.com>