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: Brandon Williams <bmwill@xxxxxxxxxx>
---
Documentation/config.txt | 17 +++++++++++
Documentation/git.txt | 6 ++++
Makefile | 1 +
cache.h | 8 +++++
protocol.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++
protocol.h | 33 ++++++++++++++++++++
6 files changed, 144 insertions(+)
create mode 100644 protocol.c
create mode 100644 protocol.h
diff --git a/Documentation/config.txt b/Documentation/config.txt
index dc4e3f58a..b78747abc 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -2517,6 +2517,23 @@ The protocol names currently used by git are:
`hg` to allow the `git-remote-hg` helper)
--
+protocol.version::
+ 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.
+
+--
+
pull.ff::
By default, Git does not create an extra merge commit when merging
a commit that is a descendant of the current commit. Instead, the
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 6e3a6767e..7518ea3af 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -697,6 +697,12 @@ of clones and fetches.
which feed potentially-untrusted URLS to git commands. See
linkgit:git-config[1] for more details.
+`GIT_PROTOCOL`::
+ 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
+ ignored.
+
Discussion[[Discussion]]
------------------------
diff --git a/Makefile b/Makefile
index ed4ca438b..9ce68cded 100644
--- a/Makefile
+++ b/Makefile
@@ -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
diff --git a/cache.h b/cache.h
index 49b083ee0..c74b73671 100644
--- a/cache.h
+++ b/cache.h
@@ -445,6 +445,14 @@ static inline enum object_type object_type(unsigned int mode)
#define GIT_ICASE_PATHSPECS_ENVIRONMENT "GIT_ICASE_PATHSPECS"
#define GIT_QUARANTINE_ENVIRONMENT "GIT_QUARANTINE_PATH"
+/*
+ * 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.
+ */
+#define GIT_PROTOCOL_ENVIRONMENT "GIT_PROTOCOL"
+
/*
* This environment variable is expected to contain a boolean indicating
* whether we should or should not treat:
diff --git a/protocol.c b/protocol.c
new file mode 100644
index 000000000..43012b7eb
--- /dev/null
+++ b/protocol.c
@@ -0,0 +1,79 @@
+#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;
+ else
+ 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",
+ value);
+
+ 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;
+}
diff --git a/protocol.h b/protocol.h
new file mode 100644
index 000000000..1b2bc94a8
--- /dev/null
+++ b/protocol.h
@@ -0,0 +1,33 @@
+#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 */
--
2.14.2.920.gcf0c67979c-goog
