[PATCH v2] clone: send ref-prefixes when using protocol v2

[Brandon Williams]

Teach clone to send a list of ref-prefixes, when using protocol v2, to
allow the server to filter out irrelevant references from the
ref-advertisement.  This reduces wasted time and bandwidth when cloning
repositories with a larger number of references.

Signed-off-by: Brandon Williams <bmw...@google.com>
---
 builtin/clone.c        | 20 +++++++++++++++-----
 t/t5702-protocol-v2.sh |  7 ++++++-
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index 99e73dae85..5c0adbd6d0 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -895,7 +895,8 @@ int cmd_clone(int argc, const char **argv, const char 
*prefix)
        int err = 0, complete_refs_before_fetch = 1;
        int submodule_progress;
 
-       struct refspec_item refspec;
+       struct refspec rs = REFSPEC_INIT_FETCH;
+       struct argv_array ref_prefixes = ARGV_ARRAY_INIT;
 
        fetch_if_missing = 0;
 
@@ -1077,7 +1078,7 @@ int cmd_clone(int argc, const char **argv, const char 
*prefix)
        if (option_required_reference.nr || option_optional_reference.nr)
                setup_reference();
 
-       refspec_item_init(&refspec, value.buf, REFSPEC_FETCH);
+       refspec_append(&rs, value.buf);
 
        strbuf_reset(&value);
 
@@ -1134,10 +1135,18 @@ int cmd_clone(int argc, const char **argv, const char 
*prefix)
        if (transport->smart_options && !deepen && !filter_options.choice)
                transport->smart_options->check_self_contained_and_connected = 
1;
 
-       refs = transport_get_remote_refs(transport, NULL);
+
+       argv_array_push(&ref_prefixes, "HEAD");
+       refspec_ref_prefixes(&rs, &ref_prefixes);
+       if (option_branch)
+               expand_ref_prefix(&ref_prefixes, option_branch);
+       if (!option_no_tags)
+               argv_array_push(&ref_prefixes, "refs/tags/");
+
+       refs = transport_get_remote_refs(transport, &ref_prefixes);
 
        if (refs) {
-               mapped_refs = wanted_peer_refs(refs, &refspec);
+               mapped_refs = wanted_peer_refs(refs, &rs.items[0]);
                /*
                 * transport_get_remote_refs() may return refs with null sha-1
                 * in mapped_refs (see struct transport->get_refs_list
@@ -1231,6 +1240,7 @@ int cmd_clone(int argc, const char **argv, const char 
*prefix)
        strbuf_release(&value);
        junk_mode = JUNK_LEAVE_ALL;
 
-       refspec_item_clear(&refspec);
+       refspec_clear(&rs);
+       argv_array_clear(&ref_prefixes);
        return err;
 }
diff --git a/t/t5702-protocol-v2.sh b/t/t5702-protocol-v2.sh
index a4fe6508bd..9c6ea04a69 100755
--- a/t/t5702-protocol-v2.sh
+++ b/t/t5702-protocol-v2.sh
@@ -181,7 +181,12 @@ test_expect_success 'clone with file:// using protocol v2' 
'
        test_cmp expect actual &&
 
        # Server responded using protocol v2
-       grep "clone< version 2" log
+       grep "clone< version 2" log &&
+       
+       # Client sent ref-prefixes to filter the ref-advertisement 
+       grep "ref-prefix HEAD" log &&
+       grep "ref-prefix refs/heads/" log &&
+       grep "ref-prefix refs/tags/" log
 '
 
 test_expect_success 'fetch with file:// using protocol v2' '
-- 
2.18.0.233.g985f88cf7e-goog