Teach the client to be able to request a remote's refs using protocol
v2.  This is done by having a client issue a 'ls-refs' request to a v2
server.

Signed-off-by: Brandon Williams <bmw...@google.com>
---
 builtin/upload-pack.c  |  10 ++--
 connect.c              | 123 ++++++++++++++++++++++++++++++++++++++++++++++++-
 connect.h              |   2 +
 remote.h               |   4 ++
 t/t5702-protocol-v2.sh |  53 +++++++++++++++++++++
 transport.c            |   2 +-
 6 files changed, 187 insertions(+), 7 deletions(-)
 create mode 100755 t/t5702-protocol-v2.sh

diff --git a/builtin/upload-pack.c b/builtin/upload-pack.c
index 8d53e9794..a757df8da 100644
--- a/builtin/upload-pack.c
+++ b/builtin/upload-pack.c
@@ -5,6 +5,7 @@
 #include "parse-options.h"
 #include "protocol.h"
 #include "upload-pack.h"
+#include "serve.h"
 
 static const char * const upload_pack_usage[] = {
        N_("git upload-pack [<options>] <dir>"),
@@ -16,6 +17,7 @@ int cmd_upload_pack(int argc, const char **argv, const char 
*prefix)
        const char *dir;
        int strict = 0;
        struct upload_pack_options opts = { 0 };
+       struct serve_options serve_opts = SERVE_OPTIONS_INIT;
        struct option options[] = {
                OPT_BOOL(0, "stateless-rpc", &opts.stateless_rpc,
                         N_("quit after a single request/response exchange")),
@@ -48,11 +50,9 @@ int cmd_upload_pack(int argc, const char **argv, const char 
*prefix)
 
        switch (determine_protocol_version_server()) {
        case protocol_v2:
-               /*
-                * fetch support for protocol v2 has not been implemented yet,
-                * so ignore the request to use v2 and fallback to using v0.
-                */
-               upload_pack(&opts);
+               serve_opts.advertise_capabilities = opts.advertise_refs;
+               serve_opts.stateless_rpc = opts.stateless_rpc;
+               serve(&serve_opts);
                break;
        case protocol_v1:
                /*
diff --git a/connect.c b/connect.c
index f2157a821..7cb1f1df7 100644
--- a/connect.c
+++ b/connect.c
@@ -12,9 +12,11 @@
 #include "sha1-array.h"
 #include "transport.h"
 #include "strbuf.h"
+#include "version.h"
 #include "protocol.h"
 
 static char *server_capabilities;
+static struct argv_array server_capabilities_v2 = ARGV_ARRAY_INIT;
 static const char *parse_feature_value(const char *, const char *, int *);
 
 static int check_ref(const char *name, unsigned int flags)
@@ -62,6 +64,33 @@ static void die_initial_contact(int unexpected)
                      "and the repository exists."));
 }
 
+/* Checks if the server supports the capability 'c' */
+int server_supports_v2(const char *c, int die_on_error)
+{
+       int i;
+
+       for (i = 0; i < server_capabilities_v2.argc; i++) {
+               const char *out;
+               if (skip_prefix(server_capabilities_v2.argv[i], c, &out) &&
+                   (!*out || *out == '='))
+                       return 1;
+       }
+
+       if (die_on_error)
+               die("server doesn't support '%s'", c);
+
+       return 0;
+}
+
+static void process_capabilities_v2(struct packet_reader *reader)
+{
+       while (packet_reader_read(reader) == PACKET_READ_NORMAL)
+               argv_array_push(&server_capabilities_v2, reader->line);
+
+       if (reader->status != PACKET_READ_FLUSH)
+               die("protocol error");
+}
+
 enum protocol_version discover_version(struct packet_reader *reader)
 {
        enum protocol_version version = protocol_unknown_version;
@@ -85,7 +114,7 @@ enum protocol_version discover_version(struct packet_reader 
*reader)
        /* Maybe process capabilities here, at least for v2 */
        switch (version) {
        case protocol_v2:
-               die("support for protocol v2 not implemented yet");
+               process_capabilities_v2(reader);
                break;
        case protocol_v1:
                /* Read the peeked version line */
@@ -293,6 +322,98 @@ struct ref **get_remote_heads(struct packet_reader *reader,
        return list;
 }
 
+static int process_ref_v2(const char *line, struct ref ***list)
+{
+       int ret = 1;
+       int i = 0;
+       struct object_id old_oid;
+       struct ref *ref;
+       struct string_list line_sections = STRING_LIST_INIT_DUP;
+
+       if (string_list_split(&line_sections, line, ' ', -1) < 2) {
+               ret = 0;
+               goto out;
+       }
+
+       if (get_oid_hex(line_sections.items[i++].string, &old_oid)) {
+               ret = 0;
+               goto out;
+       }
+
+       ref = alloc_ref(line_sections.items[i++].string);
+
+       oidcpy(&ref->old_oid, &old_oid);
+       **list = ref;
+       *list = &ref->next;
+
+       for (; i < line_sections.nr; i++) {
+               const char *arg = line_sections.items[i].string;
+               if (skip_prefix(arg, "symref-target:", &arg))
+                       ref->symref = xstrdup(arg);
+
+               if (skip_prefix(arg, "peeled:", &arg)) {
+                       struct object_id peeled_oid;
+                       char *peeled_name;
+                       struct ref *peeled;
+                       if (get_oid_hex(arg, &peeled_oid)) {
+                               ret = 0;
+                               goto out;
+                       }
+
+                       peeled_name = xstrfmt("%s^{}", ref->name);
+                       peeled = alloc_ref(peeled_name);
+
+                       oidcpy(&peeled->old_oid, &peeled_oid);
+                       **list = peeled;
+                       *list = &peeled->next;
+
+                       free(peeled_name);
+               }
+       }
+
+out:
+       string_list_clear(&line_sections, 0);
+       return ret;
+}
+
+struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
+                            struct ref **list, int for_push,
+                            const struct argv_array *ref_patterns)
+{
+       int i;
+       *list = NULL;
+
+       /* Check that the server supports the ls-refs command */
+       /* Issue request for ls-refs */
+       if (server_supports_v2("ls-refs", 1))
+               packet_write_fmt(fd_out, "command=ls-refs\n");
+
+       if (server_supports_v2("agent", 0))
+           packet_write_fmt(fd_out, "agent=%s", git_user_agent_sanitized());
+
+       packet_delim(fd_out);
+       /* When pushing we don't want to request the peeled tags */
+       if (!for_push)
+               packet_write_fmt(fd_out, "peel\n");
+       packet_write_fmt(fd_out, "symrefs\n");
+       for (i = 0; ref_patterns && i < ref_patterns->argc; i++) {
+               packet_write_fmt(fd_out, "ref-pattern %s\n",
+                                ref_patterns->argv[i]);
+       }
+       packet_flush(fd_out);
+
+       /* Process response from server */
+       while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
+               if (!process_ref_v2(reader->line, &list))
+                       die("invalid ls-refs response: %s", reader->line);
+       }
+
+       if (reader->status != PACKET_READ_FLUSH)
+               die("protocol error");
+
+       return list;
+}
+
 static const char *parse_feature_value(const char *feature_list, const char 
*feature, int *lenp)
 {
        int len;
diff --git a/connect.h b/connect.h
index cdb8979dc..8898d4495 100644
--- a/connect.h
+++ b/connect.h
@@ -16,4 +16,6 @@ extern int url_is_local_not_ssh(const char *url);
 struct packet_reader;
 extern enum protocol_version discover_version(struct packet_reader *reader);
 
+extern int server_supports_v2(const char *c, int die_on_error);
+
 #endif
diff --git a/remote.h b/remote.h
index 2016461df..21d0c776c 100644
--- a/remote.h
+++ b/remote.h
@@ -151,10 +151,14 @@ void free_refs(struct ref *ref);
 
 struct oid_array;
 struct packet_reader;
+struct argv_array;
 extern struct ref **get_remote_heads(struct packet_reader *reader,
                                     struct ref **list, unsigned int flags,
                                     struct oid_array *extra_have,
                                     struct oid_array *shallow_points);
+extern struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
+                                   struct ref **list, int for_push,
+                                   const struct argv_array *ref_patterns);
 
 int resolve_remote_symref(struct ref *ref, struct ref *list);
 int ref_newer(const struct object_id *new_oid, const struct object_id 
*old_oid);
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
new file mode 100755
index 000000000..1e42b5588
--- /dev/null
+++ b/t/t5702-protocol-v2.sh
@@ -0,0 +1,53 @@
+#!/bin/sh
+
+test_description='test git wire-protocol version 2'
+
+TEST_NO_CREATE_REPO=1
+
+. ./test-lib.sh
+
+# Test protocol v2 with 'git://' transport
+#
+. "$TEST_DIRECTORY"/lib-git-daemon.sh
+start_git_daemon --export-all --enable=receive-pack
+daemon_parent=$GIT_DAEMON_DOCUMENT_ROOT_PATH/parent
+
+test_expect_success 'create repo to be served by git-daemon' '
+       git init "$daemon_parent" &&
+       test_commit -C "$daemon_parent" one
+'
+
+test_expect_success 'list refs with git:// using protocol v2' '
+       GIT_TRACE_PACKET=1 git -c protocol.version=2 \
+               ls-remote --symref "$GIT_DAEMON_URL/parent" >actual 2>log &&
+
+       # Client requested to use protocol v2
+       grep "git> .*\\\0\\\0version=2\\\0$" log &&
+       # Server responded using protocol v2
+       grep "git< version 2" log &&
+
+       git ls-remote --symref "$GIT_DAEMON_URL/parent" >expect &&
+       test_cmp actual expect
+'
+
+stop_git_daemon
+
+# Test protocol v2 with 'file://' transport
+#
+test_expect_success 'create repo to be served by file:// transport' '
+       git init file_parent &&
+       test_commit -C file_parent one
+'
+
+test_expect_success 'list refs with file:// using protocol v2' '
+       GIT_TRACE_PACKET=1 git -c protocol.version=2 \
+               ls-remote --symref "file://$(pwd)/file_parent" >actual 2>log &&
+
+       # Server responded using protocol v2
+       grep "git< version 2" log &&
+
+       git ls-remote --symref "file://$(pwd)/file_parent" >expect &&
+       test_cmp actual expect
+'
+
+test_done
diff --git a/transport.c b/transport.c
index 83d9dd1df..ffc6b2614 100644
--- a/transport.c
+++ b/transport.c
@@ -204,7 +204,7 @@ static struct ref *get_refs_via_connect(struct transport 
*transport, int for_pus
        data->version = discover_version(&reader);
        switch (data->version) {
        case protocol_v2:
-               die("support for protocol v2 not implemented yet");
+               get_remote_refs(data->fd[1], &reader, &refs, for_push, NULL);
                break;
        case protocol_v1:
        case protocol_v0:
-- 
2.16.0.rc1.238.g530d649a79-goog

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