Commit 373d70ef authored by Brandon Williams's avatar Brandon Williams Committed by Junio C Hamano

protocol: introduce protocol extension mechanisms

Create protocol.{c,h} and provide functions which future servers and
clients can use to determine which protocol to use or is being used.

Also introduce the 'GIT_PROTOCOL' environment variable which will be
used to communicate a colon separated list of keys with optional values
to a server.  Unknown keys and values must be tolerated.  This mechanism
is used to communicate which version of the wire protocol a client would
like to use with a server.
Signed-off-by: default avatarBrandon Williams <[email protected]>
Signed-off-by: default avatarJunio C Hamano <[email protected]>
parent 5d2124b3
......@@ -2517,6 +2517,23 @@ The protocol names currently used by git are:
`hg` to allow the `git-remote-hg` helper)
Experimental. If set, clients will attempt to communicate with a
server using the specified protocol version. If unset, no
attempt will be made by the client to communicate using a
particular protocol version, this results in protocol version 0
being used.
Supported versions:
* `0` - the original wire protocol.
* `1` - the original wire protocol with the addition of a version string
in the initial response from the server.
By default, Git does not create an extra merge commit when merging
a commit that is a descendant of the current commit. Instead, the
......@@ -697,6 +697,12 @@ of clones and fetches.
which feed potentially-untrusted URLS to git commands. See
linkgit:git-config[1] for more details.
For internal use only. Used in handshaking the wire protocol.
Contains a colon ':' separated list of keys with optional values
'key[=value]'. Presence of unknown keys and values must be
......@@ -842,6 +842,7 @@ LIB_OBJS += pretty.o
LIB_OBJS += prio-queue.o
LIB_OBJS += progress.o
LIB_OBJS += prompt.o
LIB_OBJS += protocol.o
LIB_OBJS += quote.o
LIB_OBJS += reachable.o
LIB_OBJS += read-cache.o
......@@ -445,6 +445,14 @@ static inline enum object_type object_type(unsigned int mode)
* Environment variable used in handshaking the wire protocol.
* Contains a colon ':' separated list of keys with optional values
* 'key[=value]'. Presence of unknown keys and values must be
* ignored.
* This environment variable is expected to contain a boolean indicating
* whether we should or should not treat:
#include "cache.h"
#include "config.h"
#include "protocol.h"
static enum protocol_version parse_protocol_version(const char *value)
if (!strcmp(value, "0"))
return protocol_v0;
else if (!strcmp(value, "1"))
return protocol_v1;
return protocol_unknown_version;
enum protocol_version get_protocol_version_config(void)
const char *value;
if (!git_config_get_string_const("protocol.version", &value)) {
enum protocol_version version = parse_protocol_version(value);
if (version == protocol_unknown_version)
die("unknown value for config 'protocol.version': %s",
return version;
return protocol_v0;
enum protocol_version determine_protocol_version_server(void)
const char *git_protocol = getenv(GIT_PROTOCOL_ENVIRONMENT);
enum protocol_version version = protocol_v0;
* Determine which protocol version the client has requested. Since
* multiple 'version' keys can be sent by the client, indicating that
* the client is okay to speak any of them, select the greatest version
* that the client has requested. This is due to the assumption that
* the most recent protocol version will be the most state-of-the-art.
if (git_protocol) {
struct string_list list = STRING_LIST_INIT_DUP;
const struct string_list_item *item;
string_list_split(&list, git_protocol, ':', -1);
for_each_string_list_item(item, &list) {
const char *value;
enum protocol_version v;
if (skip_prefix(item->string, "version=", &value)) {
v = parse_protocol_version(value);
if (v > version)
version = v;
string_list_clear(&list, 0);
return version;
enum protocol_version determine_protocol_version_client(const char *server_response)
enum protocol_version version = protocol_v0;
if (skip_prefix(server_response, "version ", &server_response)) {
version = parse_protocol_version(server_response);
if (version == protocol_unknown_version)
die("server is speaking an unknown protocol");
if (version == protocol_v0)
die("protocol error: server explicitly said version 0");
return version;
#ifndef PROTOCOL_H
#define PROTOCOL_H
enum protocol_version {
protocol_unknown_version = -1,
protocol_v0 = 0,
protocol_v1 = 1,
* Used by a client to determine which protocol version to request be used when
* communicating with a server, reflecting the configured value of the
* 'protocol.version' config. If unconfigured, a value of 'protocol_v0' is
* returned.
extern enum protocol_version get_protocol_version_config(void);
* Used by a server to determine which protocol version should be used based on
* a client's request, communicated via the 'GIT_PROTOCOL' environment variable
* by setting appropriate values for the key 'version'. If a client doesn't
* request a particular protocol version, a default of 'protocol_v0' will be
* used.
extern enum protocol_version determine_protocol_version_server(void);
* Used by a client to determine which protocol version the server is speaking
* based on the server's initial response.
extern enum protocol_version determine_protocol_version_client(const char *server_response);
#endif /* PROTOCOL_H */
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