Implement ref-in-want on the client side so that when a server supports
the "ref-in-want" feature, a client will send "want-ref" lines for each
reference the client wants to fetch. This feature allows clients to
tolerate inconsistencies that exist when a remote repository's refs
change during the course of negotiation.
This allows a client to request to request a particular ref without
specifying the OID of the ref. This means that instead of hitting an
error when a ref no longer points at the OID it did at the beginning of
negotiation, negotiation can continue and the value of that ref will be
sent at the termination of negotiation, just before a packfile is sent.
More information on the ref-in-want feature can be found in
Documentation/technical/protocol-v2.txt.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add tests to check the behavior of fetching from a repository which
changes between rounds of negotiation (for example, when different
servers in a load-balancing agreement participate in the same stateless
RPC negotiation). This forms a baseline of comparison to the ref-in-want
functionality (which will be introduced to the client in subsequent
commits), and ensures that subsequent commits do not change existing
behavior.
As part of this effort, a mechanism to substitute strings in a single
HTTP response is added.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Currently, while performing packfile negotiation, clients are only
allowed to specify their desired objects using object ids. This causes
a vulnerability to failure when an object turns non-existent during
negotiation, which may happen if, for example, the desired repository is
provided by multiple Git servers in a load-balancing arrangement and
there exists replication delay.
In order to eliminate this vulnerability, implement the ref-in-want
feature for the 'fetch' command in protocol version 2. This feature
enables the 'fetch' command to support requests in the form of ref names
through a new "want-ref <ref>" parameter. At the conclusion of
negotiation, the server will send a list of all of the wanted references
(as provided by "want-ref" lines) in addition to the generated packfile.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
