Merge branch 'jt/connectivity-check-after-unshallow'

"git fetch" failed to correctly validate the set of objects it
received when making a shallow history deeper, which has been
corrected.

* jt/connectivity-check-after-unshallow:
  fetch-pack: write shallow, then check connectivity
  fetch-pack: implement ref-in-want
  fetch-pack: put shallow info in output parameter
  fetch: refactor to make function args narrower
  fetch: refactor fetch_refs into two functions
  fetch: refactor the population of peer ref OIDs
  upload-pack: test negotiation with changing repository
  upload-pack: implement ref-in-want
  test-pkt-line: add unpack-sideband subcommand

Documentation/config.txt

@@ -3489,6 +3489,13 @@ Note that this configuration variable is ignored if it is seen in the
 repository-level config (this is a safety measure against fetching from
 untrusted repositories).
 
+uploadpack.allowRefInWant::
+	If this option is set, `upload-pack` will support the `ref-in-want`
+	feature of the protocol version 2 `fetch` command.  This feature
+	is intended for the benefit of load-balanced servers which may
+	not have the same view of what OIDs their refs point to due to
+	replication delay.
+
 url.<base>.insteadOf::
 	Any URL that starts with this value will be rewritten to
 	start, instead, with <base>. In cases where some site serves a

Documentation/technical/protocol-v2.txt

@@ -298,12 +298,21 @@ included in the client's request:
 	for use with partial clone and partial fetch operations. See
 	`rev-list` for possible "filter-spec" values.
 
+If the 'ref-in-want' feature is advertised, the following argument can
+be included in the client's request as well as the potential addition of
+the 'wanted-refs' section in the server's response as explained below.
+
+    want-ref <ref>
+	Indicates to the server that the client wants to retrieve a
+	particular ref, where <ref> is the full name of a ref on the
+	server.
+
 The response of `fetch` is broken into a number of sections separated by
 delimiter packets (0001), with each section beginning with its section
 header.
 
     output = *section
-    section = (acknowledgments | shallow-info | packfile)
+    section = (acknowledgments | shallow-info | wanted-refs | packfile)
 	      (flush-pkt | delim-pkt)
 
     acknowledgments = PKT-LINE("acknowledgments" LF)
@@ -318,6 +327,10 @@ header.
     shallow = "shallow" SP obj-id
     unshallow = "unshallow" SP obj-id
 
+    wanted-refs = PKT-LINE("wanted-refs" LF)
+		  *PKT-LINE(wanted-ref LF)
+    wanted-ref = obj-id SP refname
+
     packfile = PKT-LINE("packfile" LF)
 	       *PKT-LINE(%x01-03 *%x00-ff)
 
@@ -378,6 +391,19 @@ header.
 	* This section is only included if a packfile section is also
 	  included in the response.
 
+    wanted-refs section
+	* This section is only included if the client has requested a
+	  ref using a 'want-ref' line and if a packfile section is also
+	  included in the response.
+
+	* Always begins with the section header "wanted-refs".
+
+	* The server will send a ref listing ("<oid> <refname>") for
+	  each reference requested using 'want-ref' lines.
+
+	* The server MUST NOT send any refs which were not requested
+	  using 'want-ref' lines.
+
     packfile section
 	* This section is only included if the client has sent 'want'
 	  lines in its request and either requested that no more

builtin/clone.c

@@ -1156,7 +1156,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 			}
 
 		if (!is_local && !complete_refs_before_fetch)
-			transport_fetch_refs(transport, mapped_refs);
+			transport_fetch_refs(transport, mapped_refs, NULL);
 
 		remote_head = find_ref_by_name(refs, "HEAD");
 		remote_head_points_at =
@@ -1198,7 +1198,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (is_local)
 		clone_local(path, git_dir);
 	else if (refs && complete_refs_before_fetch)
-		transport_fetch_refs(transport, mapped_refs);
+		transport_fetch_refs(transport, mapped_refs, NULL);
 
 	update_remote_refs(refs, mapped_refs, remote_head_points_at,
 			   branch_top.buf, reflog_msg.buf, transport,

builtin/fetch.c

@@ -242,7 +242,7 @@ static int will_fetch(struct ref **head, const unsigned char *sha1)
 	return 0;
 }
 
-static void find_non_local_tags(struct transport *transport,
+static void find_non_local_tags(const struct ref *refs,
 				struct ref **head,
 				struct ref ***tail)
 {
@@ -252,7 +252,7 @@ static void find_non_local_tags(struct transport *transport,
 	struct string_list_item *item = NULL;
 
 	for_each_ref(add_existing, &existing_refs);
-	for (ref = transport_get_remote_refs(transport, NULL); ref; ref = ref->next) {
+	for (ref = refs; ref; ref = ref->next) {
 		if (!starts_with(ref->name, "refs/tags/"))
 			continue;
 
@@ -326,7 +326,8 @@ static void find_non_local_tags(struct transport *transport,
 	string_list_clear(&remote_refs, 0);
 }
 
-static struct ref *get_ref_map(struct transport *transport,
+static struct ref *get_ref_map(struct remote *remote,
+			       const struct ref *remote_refs,
 			       struct refspec *rs,
 			       int tags, int *autotags)
 {
@@ -334,26 +335,11 @@ static struct ref *get_ref_map(struct transport *transport,
 	struct ref *rm;
 	struct ref *ref_map = NULL;
 	struct ref **tail = &ref_map;
-	struct argv_array ref_prefixes = ARGV_ARRAY_INIT;
 
 	/* opportunistically-updated references: */
 	struct ref *orefs = NULL, **oref_tail = &orefs;
 
-	const struct ref *remote_refs;
+	struct string_list existing_refs = STRING_LIST_INIT_DUP;
-
-	if (rs->nr)
-		refspec_ref_prefixes(rs, &ref_prefixes);
-	else if (transport->remote && transport->remote->fetch.nr)
-		refspec_ref_prefixes(&transport->remote->fetch, &ref_prefixes);
-
-	if (ref_prefixes.argc &&
-	    (tags == TAGS_SET || (tags == TAGS_DEFAULT && !rs->nr))) {
-		argv_array_push(&ref_prefixes, "refs/tags/");
-	}
-
-	remote_refs = transport_get_remote_refs(transport, &ref_prefixes);
-
-	argv_array_clear(&ref_prefixes);
 
 	if (rs->nr) {
 		struct refspec *fetch_refspec;
@@ -390,7 +376,7 @@ static struct ref *get_ref_map(struct transport *transport,
 		if (refmap.nr)
 			fetch_refspec = &refmap;
 		else
-			fetch_refspec = &transport->remote->fetch;
+			fetch_refspec = &remote->fetch;
 
 		for (i = 0; i < fetch_refspec->nr; i++)
 			get_fetch_map(ref_map, &fetch_refspec->items[i], &oref_tail, 1);
@@ -398,7 +384,6 @@ static struct ref *get_ref_map(struct transport *transport,
 		die("--refmap option is only meaningful with command-line refspec(s).");
 	} else {
 		/* Use the defaults */
-		struct remote *remote = transport->remote;
 		struct branch *branch = branch_get(NULL);
 		int has_merge = branch_has_merge_config(branch);
 		if (remote &&
@@ -437,7 +422,7 @@ static struct ref *get_ref_map(struct transport *transport,
 		/* also fetch all tags */
 		get_fetch_map(remote_refs, tag_refspec, &tail, 0);
 	else if (tags == TAGS_DEFAULT && *autotags)
-		find_non_local_tags(transport, &ref_map, &tail);
+		find_non_local_tags(remote_refs, &ref_map, &tail);
 
 	/* Now append any refs to be updated opportunistically: */
 	*tail = orefs;
@@ -446,7 +431,23 @@ static struct ref *get_ref_map(struct transport *transport,
 		tail = &rm->next;
 	}
 
-	return ref_remove_duplicates(ref_map);
+	ref_map = ref_remove_duplicates(ref_map);
+
+	for_each_ref(add_existing, &existing_refs);
+	for (rm = ref_map; rm; rm = rm->next) {
+		if (rm->peer_ref) {
+			struct string_list_item *peer_item =
+				string_list_lookup(&existing_refs,
+						   rm->peer_ref->name);
+			if (peer_item) {
+				struct object_id *old_oid = peer_item->util;
+				oidcpy(&rm->peer_ref->old_oid, old_oid);
+			}
+		}
+	}
+	string_list_clear(&existing_refs, 1);
+
+	return ref_map;
 }
 
 #define STORE_REF_ERROR_OTHER 1
@@ -756,7 +757,7 @@ static int iterate_ref_map(void *cb_data, struct object_id *oid)
 }
 
 static int store_updated_refs(const char *raw_url, const char *remote_name,
-		struct ref *ref_map)
+			      int connectivity_checked, struct ref *ref_map)
 {
 	FILE *fp;
 	struct commit *commit;
@@ -778,11 +779,13 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 	else
 		url = xstrdup("foreign");
 
+	if (!connectivity_checked) {
 		rm = ref_map;
 		if (check_connected(iterate_ref_map, &rm, NULL)) {
 			rc = error(_("%s did not send all necessary objects\n"), url);
 			goto abort;
 		}
+	}
 
 	prepare_format_display(ref_map);
 
@@ -933,14 +936,31 @@ static int quickfetch(struct ref *ref_map)
 	return check_connected(iterate_ref_map, &rm, &opt);
 }
 
-static int fetch_refs(struct transport *transport, struct ref *ref_map)
+static int fetch_refs(struct transport *transport, struct ref *ref_map,
+		      struct ref **updated_remote_refs)
 {
 	int ret = quickfetch(ref_map);
 	if (ret)
-		ret = transport_fetch_refs(transport, ref_map);
+		ret = transport_fetch_refs(transport, ref_map,
+					   updated_remote_refs);
 	if (!ret)
-		ret |= store_updated_refs(transport->url,
+		/*
+		 * Keep the new pack's ".keep" file around to allow the caller
+		 * time to update refs to reference the new objects.
+		 */
+		return 0;
+	transport_unlock_pack(transport);
+	return ret;
+}
+
+/* Update local refs based on the ref values fetched from a remote */
+static int consume_refs(struct transport *transport, struct ref *ref_map)
+{
+	int connectivity_checked = transport->smart_options
+		? transport->smart_options->connectivity_checked : 0;
+	int ret = store_updated_refs(transport->url,
 				     transport->remote->name,
+				     connectivity_checked,
 				     ref_map);
 	transport_unlock_pack(transport);
 	return ret;
@@ -1087,7 +1107,8 @@ static void backfill_tags(struct transport *transport, struct ref *ref_map)
 	transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, NULL);
 	transport_set_option(transport, TRANS_OPT_DEPTH, "0");
 	transport_set_option(transport, TRANS_OPT_DEEPEN_RELATIVE, NULL);
-	fetch_refs(transport, ref_map);
+	if (!fetch_refs(transport, ref_map, NULL))
+		consume_refs(transport, ref_map);
 
 	if (gsecondary) {
 		transport_disconnect(gsecondary);
@@ -1098,13 +1119,12 @@ static void backfill_tags(struct transport *transport, struct ref *ref_map)
 static int do_fetch(struct transport *transport,
 		    struct refspec *rs)
 {
-	struct string_list existing_refs = STRING_LIST_INIT_DUP;
 	struct ref *ref_map;
-	struct ref *rm;
 	int autotags = (transport->remote->fetch_tags == 1);
 	int retcode = 0;
-
+	const struct ref *remote_refs;
-	for_each_ref(add_existing, &existing_refs);
+	struct ref *updated_remote_refs = NULL;
+	struct argv_array ref_prefixes = ARGV_ARRAY_INIT;
 
 	if (tags == TAGS_DEFAULT) {
 		if (transport->remote->fetch_tags == 2)
@@ -1120,22 +1140,24 @@ static int do_fetch(struct transport *transport,
 			goto cleanup;
 	}
 
-	ref_map = get_ref_map(transport, rs, tags, &autotags);
+	if (rs->nr)
+		refspec_ref_prefixes(rs, &ref_prefixes);
+	else if (transport->remote && transport->remote->fetch.nr)
+		refspec_ref_prefixes(&transport->remote->fetch, &ref_prefixes);
+
+	if (ref_prefixes.argc &&
+	    (tags == TAGS_SET || (tags == TAGS_DEFAULT && !rs->nr))) {
+		argv_array_push(&ref_prefixes, "refs/tags/");
+	}
+
+	remote_refs = transport_get_remote_refs(transport, &ref_prefixes);
+	argv_array_clear(&ref_prefixes);
+
+	ref_map = get_ref_map(transport->remote, remote_refs, rs,
+			      tags, &autotags);
 	if (!update_head_ok)
 		check_not_current_branch(ref_map);
 
-	for (rm = ref_map; rm; rm = rm->next) {
-		if (rm->peer_ref) {
-			struct string_list_item *peer_item =
-				string_list_lookup(&existing_refs,
-						   rm->peer_ref->name);
-			if (peer_item) {
-				struct object_id *old_oid = peer_item->util;
-				oidcpy(&rm->peer_ref->old_oid, old_oid);
-			}
-		}
-	}
-
 	if (tags == TAGS_DEFAULT && autotags)
 		transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, "1");
 	if (prune) {
@@ -1152,7 +1174,24 @@ static int do_fetch(struct transport *transport,
 				   transport->url);
 		}
 	}
-	if (fetch_refs(transport, ref_map)) {
+
+	if (fetch_refs(transport, ref_map, &updated_remote_refs)) {
+		free_refs(ref_map);
+		retcode = 1;
+		goto cleanup;
+	}
+	if (updated_remote_refs) {
+		/*
+		 * Regenerate ref_map using the updated remote refs.  This is
+		 * to account for additional information which may be provided
+		 * by the transport (e.g. shallow info).
+		 */
+		free_refs(ref_map);
+		ref_map = get_ref_map(transport->remote, updated_remote_refs, rs,
+				      tags, &autotags);
+		free_refs(updated_remote_refs);
+	}
+	if (consume_refs(transport, ref_map)) {
 		free_refs(ref_map);
 		retcode = 1;
 		goto cleanup;
@@ -1164,14 +1203,13 @@ static int do_fetch(struct transport *transport,
 	if (tags == TAGS_DEFAULT && autotags) {
 		struct ref **tail = &ref_map;
 		ref_map = NULL;
-		find_non_local_tags(transport, &ref_map, &tail);
+		find_non_local_tags(remote_refs, &ref_map, &tail);
 		if (ref_map)
 			backfill_tags(transport, ref_map);
 		free_refs(ref_map);
 	}
 
  cleanup:
-	string_list_clear(&existing_refs, 1);
 	return retcode;
 }
 

connected.c

@@ -58,8 +58,10 @@ int check_connected(oid_iterate_fn fn, void *cb_data,
 	argv_array_push(&rev_list.args, "--stdin");
 	if (repository_format_partial_clone)
 		argv_array_push(&rev_list.args, "--exclude-promisor-objects");
+	if (!opt->is_deepening_fetch) {
 		argv_array_push(&rev_list.args, "--not");
 		argv_array_push(&rev_list.args, "--all");
+	}
 	argv_array_push(&rev_list.args, "--quiet");
 	if (opt->progress)
 		argv_array_pushf(&rev_list.args, "--progress=%s",

connected.h

@@ -38,6 +38,13 @@ struct check_connected_options {
 	 * Insert these variables into the environment of the child process.
 	 */
 	const char **env;
+
+	/*
+	 * If non-zero, check the ancestry chain completely, not stopping at
+	 * any existing ref. This is necessary when deepening existing refs
+	 * during a fetch.
+	 */
+	unsigned is_deepening_fetch : 1;
 };
 
 #define CHECK_CONNECTED_INIT { 0 }

fetch-object.c

@@ -19,7 +19,7 @@ static void fetch_refs(const char *remote_name, struct ref *ref)
 
 	transport_set_option(transport, TRANS_OPT_FROM_PROMISOR, "1");
 	transport_set_option(transport, TRANS_OPT_NO_DEPENDENTS, "1");
-	transport_fetch_refs(transport, ref);
+	transport_fetch_refs(transport, ref, NULL);
 	fetch_if_missing = original_fetch_if_missing;
 }
 

fetch-pack.c

@@ -20,6 +20,7 @@
 #include "oidset.h"
 #include "packfile.h"
 #include "object-store.h"
+#include "connected.h"
 
 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
@@ -1103,9 +1104,10 @@ static void add_shallow_requests(struct strbuf *req_buf,
 
 static void add_wants(const struct ref *wants, struct strbuf *req_buf)
 {
+	int use_ref_in_want = server_supports_feature("fetch", "ref-in-want", 0);
+
 	for ( ; wants ; wants = wants->next) {
 		const struct object_id *remote = &wants->old_oid;
-		const char *remote_hex;
 		struct object *o;
 
 		/*
@@ -1123,8 +1125,10 @@ static void add_wants(const struct ref *wants, struct strbuf *req_buf)
 			continue;
 		}
 
-		remote_hex = oid_to_hex(remote);
+		if (!use_ref_in_want || wants->exact_oid)
-		packet_buf_write(req_buf, "want %s\n", remote_hex);
+			packet_buf_write(req_buf, "want %s\n", oid_to_hex(remote));
+		else
+			packet_buf_write(req_buf, "want-ref %s\n", wants->name);
 	}
 }
 
@@ -1335,6 +1339,32 @@ static void receive_shallow_info(struct fetch_pack_args *args,
 	args->deepen = 1;
 }
 
+static void receive_wanted_refs(struct packet_reader *reader, struct ref *refs)
+{
+	process_section_header(reader, "wanted-refs", 0);
+	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
+		struct object_id oid;
+		const char *end;
+		struct ref *r = NULL;
+
+		if (parse_oid_hex(reader->line, &oid, &end) || *end++ != ' ')
+			die("expected wanted-ref, got '%s'", reader->line);
+
+		for (r = refs; r; r = r->next) {
+			if (!strcmp(end, r->name)) {
+				oidcpy(&r->old_oid, &oid);
+				break;
+			}
+		}
+
+		if (!r)
+			die("unexpected wanted-ref: '%s'", reader->line);
+	}
+
+	if (reader->status != PACKET_READ_DELIM)
+		die("error processing wanted refs: %d", reader->status);
+}
+
 enum fetch_state {
 	FETCH_CHECK_LOCAL = 0,
 	FETCH_SEND_REQUEST,
@@ -1409,6 +1439,9 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			if (process_section_header(&reader, "shallow-info", 1))
 				receive_shallow_info(args, &reader);
 
+			if (process_section_header(&reader, "wanted-refs", 1))
+				receive_wanted_refs(&reader, ref);
+
 			/* get the pack */
 			process_section_header(&reader, "packfile", 0);
 			if (get_pack(args, fd, pack_lockfile))
@@ -1471,12 +1504,13 @@ static int remove_duplicates_in_refs(struct ref **ref, int nr)
 }
 
 static void update_shallow(struct fetch_pack_args *args,
-			   struct ref **sought, int nr_sought,
+			   struct ref *refs,
 			   struct shallow_info *si)
 {
 	struct oid_array ref = OID_ARRAY_INIT;
 	int *status;
 	int i;
+	struct ref *r;
 
 	if (args->deepen && alternate_shallow_file) {
 		if (*alternate_shallow_file == '\0') { /* --unshallow */
@@ -1518,8 +1552,8 @@ static void update_shallow(struct fetch_pack_args *args,
 	remove_nonexistent_theirs_shallow(si);
 	if (!si->nr_ours && !si->nr_theirs)
 		return;
-	for (i = 0; i < nr_sought; i++)
+	for (r = refs; r; r = r->next)
-		oid_array_append(&ref, &sought[i]->old_oid);
+		oid_array_append(&ref, &r->old_oid);
 	si->ref = &ref;
 
 	if (args->update_shallow) {
@@ -1553,17 +1587,29 @@ static void update_shallow(struct fetch_pack_args *args,
 	 * remote is also shallow, check what ref is safe to update
 	 * without updating .git/shallow
 	 */
-	status = xcalloc(nr_sought, sizeof(*status));
+	status = xcalloc(ref.nr, sizeof(*status));
 	assign_shallow_commits_to_refs(si, NULL, status);
 	if (si->nr_ours || si->nr_theirs) {
-		for (i = 0; i < nr_sought; i++)
+		for (r = refs, i = 0; r; r = r->next, i++)
 			if (status[i])
-				sought[i]->status = REF_STATUS_REJECT_SHALLOW;
+				r->status = REF_STATUS_REJECT_SHALLOW;
 	}
 	free(status);
 	oid_array_clear(&ref);
 }
 
+static int iterate_ref_map(void *cb_data, struct object_id *oid)
+{
+	struct ref **rm = cb_data;
+	struct ref *ref = *rm;
+
+	if (!ref)
+		return -1; /* end of the list */
+	*rm = ref->next;
+	oidcpy(oid, &ref->old_oid);
+	return 0;
+}
+
 struct ref *fetch_pack(struct fetch_pack_args *args,
 		       int fd[], struct child_process *conn,
 		       const struct ref *ref,
@@ -1592,7 +1638,25 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		ref_cpy = do_fetch_pack(args, fd, ref, sought, nr_sought,
 					&si, pack_lockfile);
 	reprepare_packed_git(the_repository);
-	update_shallow(args, sought, nr_sought, &si);
+
+	if (!args->cloning && args->deepen) {
+		struct check_connected_options opt = CHECK_CONNECTED_INIT;
+		struct ref *iterator = ref_cpy;
+		opt.shallow_file = alternate_shallow_file;
+		if (args->deepen)
+			opt.is_deepening_fetch = 1;
+		if (check_connected(iterate_ref_map, &iterator, &opt)) {
+			error(_("remote did not send all necessary objects"));
+			free_refs(ref_cpy);
+			ref_cpy = NULL;
+			rollback_lock_file(&shallow_lock);
+			goto cleanup;
+		}
+		args->connectivity_checked = 1;
+	}
+
+	update_shallow(args, ref_cpy, &si);
+cleanup:
 	clear_shallow_info(&si);
 	return ref_cpy;
 }

fetch-pack.h

@@ -41,6 +41,21 @@ struct fetch_pack_args {
 	 * regardless of which object flags it uses (if any).
 	 */
 	unsigned no_dependents:1;
+
+	/*
+	 * Because fetch_pack() overwrites the shallow file upon a
+	 * successful deepening non-clone fetch, if this struct
+	 * specifies such a fetch, fetch_pack() needs to perform a
+	 * connectivity check before deciding if a fetch is successful
+	 * (and overwriting the shallow file). fetch_pack() sets this
+	 * field to 1 if such a connectivity check was performed.
+	 *
+	 * This is different from check_self_contained_and_connected
+	 * in that the former allows existing objects in the
+	 * repository to satisfy connectivity needs, whereas the
+	 * latter doesn't.
+	 */
+	unsigned connectivity_checked:1;
 };
 
 /*

remote.c

@@ -1736,6 +1736,7 @@ int get_fetch_map(const struct ref *remote_refs,
 		if (refspec->exact_sha1) {
 			ref_map = alloc_ref(name);
 			get_oid_hex(name, &ref_map->old_oid);
+			ref_map->exact_oid = 1;
 		} else {
 			ref_map = get_remote_ref(remote_refs, name);
 		}

remote.h

@@ -73,6 +73,7 @@ struct ref {
 		force:1,
 		forced_update:1,
 		expect_old_sha1:1,
+		exact_oid:1,
 		deletion:1;
 
 	enum {

t/helper/test-pkt-line.c

@@ -1,3 +1,4 @@
+#include "cache.h"
 #include "pkt-line.h"
 
 static void pack_line(const char *line)
@@ -48,6 +49,36 @@ static void unpack(void)
 	}
 }
 
+static void unpack_sideband(void)
+{
+	struct packet_reader reader;
+	packet_reader_init(&reader, 0, NULL, 0,
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_CHOMP_NEWLINE);
+
+	while (packet_reader_read(&reader) != PACKET_READ_EOF) {
+		int band;
+		int fd;
+
+		switch (reader.status) {
+		case PACKET_READ_EOF:
+			break;
+		case PACKET_READ_NORMAL:
+			band = reader.line[0] & 0xff;
+			if (band < 1 || band > 2)
+				die("unexpected side band %d", band);
+			fd = band;
+
+			write_or_die(fd, reader.line + 1, reader.pktlen - 1);
+			break;
+		case PACKET_READ_FLUSH:
+			return;
+		case PACKET_READ_DELIM:
+			break;
+		}
+	}
+}
+
 int cmd_main(int argc, const char **argv)
 {
 	if (argc < 2)
@@ -57,6 +88,8 @@ int cmd_main(int argc, const char **argv)
 		pack(argc - 2, argv + 2);
 	else if (!strcmp(argv[1], "unpack"))
 		unpack();
+	else if (!strcmp(argv[1], "unpack-sideband"))
+		unpack_sideband();
 	else
 		die("invalid argument '%s'", argv[1]);
 

t/lib-httpd.sh

@@ -132,6 +132,7 @@ prepare_httpd() {
 	cp "$TEST_PATH"/passwd "$HTTPD_ROOT_PATH"
 	install_script broken-smart-http.sh
 	install_script error.sh
+	install_script apply-one-time-sed.sh
 
 	ln -s "$LIB_HTTPD_MODULE_PATH" "$HTTPD_ROOT_PATH/modules"
 

t/lib-httpd/apache.conf

@@ -111,9 +111,14 @@ Alias /auth/dumb/ www/auth/dumb/
 	SetEnv GIT_EXEC_PATH ${GIT_EXEC_PATH}
 	SetEnv GIT_HTTP_EXPORT_ALL
 </LocationMatch>
+<LocationMatch /one_time_sed/>
+	SetEnv GIT_EXEC_PATH ${GIT_EXEC_PATH}
+	SetEnv GIT_HTTP_EXPORT_ALL
+</LocationMatch>
 ScriptAliasMatch /smart_*[^/]*/(.*) ${GIT_EXEC_PATH}/git-http-backend/$1
 ScriptAlias /broken_smart/ broken-smart-http.sh/
 ScriptAlias /error/ error.sh/
+ScriptAliasMatch /one_time_sed/(.*) apply-one-time-sed.sh/$1
 <Directory ${GIT_EXEC_PATH}>
 	Options FollowSymlinks
 </Directory>
@@ -123,6 +128,9 @@ ScriptAlias /error/ error.sh/
 <Files error.sh>
   Options ExecCGI
 </Files>
+<Files apply-one-time-sed.sh>
+	Options ExecCGI
+</Files>
 <Files ${GIT_EXEC_PATH}/git-http-backend>
 	Options ExecCGI
 </Files>

t/lib-httpd/apply-one-time-sed.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+# If "one-time-sed" exists in $HTTPD_ROOT_PATH, run sed on the HTTP response,
+# using the contents of "one-time-sed" as the sed command to be run. If the
+# response was modified as a result, delete "one-time-sed" so that subsequent
+# HTTP responses are no longer modified.
+#
+# This can be used to simulate the effects of the repository changing in
+# between HTTP request-response pairs.
+if [ -e one-time-sed ]; then
+	"$GIT_EXEC_PATH/git-http-backend" >out
+	sed "$(cat one-time-sed)" <out >out_modified
+
+	if diff out out_modified >/dev/null; then
+		cat out
+	else
+		cat out_modified
+		rm one-time-sed
+	fi
+else
+	"$GIT_EXEC_PATH/git-http-backend"
+fi

t/t5537-fetch-shallow.sh

@@ -186,4 +186,47 @@ EOF
 	test_cmp expect actual
 '
 
+. "$TEST_DIRECTORY"/lib-httpd.sh
+start_httpd
+
+REPO="$HTTPD_DOCUMENT_ROOT_PATH/repo"
+
+test_expect_success 'shallow fetches check connectivity before writing shallow file' '
+	rm -rf "$REPO" client &&
+
+	git init "$REPO" &&
+	test_commit -C "$REPO" one &&
+	test_commit -C "$REPO" two &&
+	test_commit -C "$REPO" three &&
+
+	git init client &&
+
+	# Use protocol v2 to ensure that shallow information is sent exactly
+	# once by the server, since we are planning to manipulate it.
+	git -C "$REPO" config protocol.version 2 &&
+	git -C client config protocol.version 2 &&
+
+	git -C client fetch --depth=2 "$HTTPD_URL/one_time_sed/repo" master:a_branch &&
+
+	# Craft a situation in which the server sends back an unshallow request
+	# with an empty packfile. This is done by refetching with a shorter
+	# depth (to ensure that the packfile is empty), and overwriting the
+	# shallow line in the response with the unshallow line we want.
+	printf "s/0034shallow %s/0036unshallow %s/" \
+	       "$(git -C "$REPO" rev-parse HEAD)" \
+	       "$(git -C "$REPO" rev-parse HEAD^)" \
+	       >"$HTTPD_ROOT_PATH/one-time-sed" &&
+	test_must_fail git -C client fetch --depth=1 "$HTTPD_URL/one_time_sed/repo" \
+		master:a_branch &&
+
+	# Ensure that the one-time-sed script was used.
+	! test -e "$HTTPD_ROOT_PATH/one-time-sed" &&
+
+	# Ensure that the resulting repo is consistent, despite our failure to
+	# fetch.
+	git -C client fsck
+'
+
+stop_httpd
+
 test_done

t/t5703-upload-pack-ref-in-want.sh

@@ -0,0 +1,377 @@
+#!/bin/sh
+
+test_description='upload-pack ref-in-want'
+
+. ./test-lib.sh
+
+get_actual_refs () {
+	sed -n -e '/wanted-refs/,/0001/{
+		/wanted-refs/d
+		/0001/d
+		p
+		}' <out | test-pkt-line unpack >actual_refs
+}
+
+get_actual_commits () {
+	sed -n -e '/packfile/,/0000/{
+		/packfile/d
+		p
+		}' <out | test-pkt-line unpack-sideband >o.pack &&
+	git index-pack o.pack &&
+	git verify-pack -v o.idx | grep commit | cut -c-40 | sort >actual_commits
+}
+
+check_output () {
+	get_actual_refs &&
+	test_cmp expected_refs actual_refs &&
+	get_actual_commits &&
+	test_cmp expected_commits actual_commits
+}
+
+# c(o/foo) d(o/bar)
+#        \ /
+#         b   e(baz)  f(master)
+#          \__  |  __/
+#             \ | /
+#               a
+test_expect_success 'setup repository' '
+	test_commit a &&
+	git checkout -b o/foo &&
+	test_commit b &&
+	test_commit c &&
+	git checkout -b o/bar b &&
+	test_commit d &&
+	git checkout -b baz a &&
+	test_commit e &&
+	git checkout master &&
+	test_commit f
+'
+
+test_expect_success 'config controls ref-in-want advertisement' '
+	git serve --advertise-capabilities >out &&
+	! grep -a ref-in-want out &&
+
+	git config uploadpack.allowRefInWant false &&
+	git serve --advertise-capabilities >out &&
+	! grep -a ref-in-want out &&
+
+	git config uploadpack.allowRefInWant true &&
+	git serve --advertise-capabilities >out &&
+	grep -a ref-in-want out
+'
+
+test_expect_success 'invalid want-ref line' '
+	test-pkt-line pack >in <<-EOF &&
+	command=fetch
+	0001
+	no-progress
+	want-ref refs/heads/non-existent
+	done
+	0000
+	EOF
+
+	test_must_fail git serve --stateless-rpc 2>out <in &&
+	grep "unknown ref" out
+'
+
+test_expect_success 'basic want-ref' '
+	cat >expected_refs <<-EOF &&
+	$(git rev-parse f) refs/heads/master
+	EOF
+	git rev-parse f | sort >expected_commits &&
+
+	test-pkt-line pack >in <<-EOF &&
+	command=fetch
+	0001
+	no-progress
+	want-ref refs/heads/master
+	have $(git rev-parse a)
+	done
+	0000
+	EOF
+
+	git serve --stateless-rpc >out <in &&
+	check_output
+'
+
+test_expect_success 'multiple want-ref lines' '
+	cat >expected_refs <<-EOF &&
+	$(git rev-parse c) refs/heads/o/foo
+	$(git rev-parse d) refs/heads/o/bar
+	EOF
+	git rev-parse c d | sort >expected_commits &&
+
+	test-pkt-line pack >in <<-EOF &&
+	command=fetch
+	0001
+	no-progress
+	want-ref refs/heads/o/foo
+	want-ref refs/heads/o/bar
+	have $(git rev-parse b)
+	done
+	0000
+	EOF
+
+	git serve --stateless-rpc >out <in &&
+	check_output
+'
+
+test_expect_success 'mix want and want-ref' '
+	cat >expected_refs <<-EOF &&
+	$(git rev-parse f) refs/heads/master
+	EOF
+	git rev-parse e f | sort >expected_commits &&
+
+	test-pkt-line pack >in <<-EOF &&
+	command=fetch
+	0001
+	no-progress
+	want-ref refs/heads/master
+	want $(git rev-parse e)
+	have $(git rev-parse a)
+	done
+	0000
+	EOF
+
+	git serve --stateless-rpc >out <in &&
+	check_output
+'
+
+test_expect_success 'want-ref with ref we already have commit for' '
+	cat >expected_refs <<-EOF &&
+	$(git rev-parse c) refs/heads/o/foo
+	EOF
+	>expected_commits &&
+
+	test-pkt-line pack >in <<-EOF &&
+	command=fetch
+	0001
+	no-progress
+	want-ref refs/heads/o/foo
+	have $(git rev-parse c)
+	done
+	0000
+	EOF
+
+	git serve --stateless-rpc >out <in &&
+	check_output
+'
+
+. "$TEST_DIRECTORY"/lib-httpd.sh
+start_httpd
+
+REPO="$HTTPD_DOCUMENT_ROOT_PATH/repo"
+LOCAL_PRISTINE="$(pwd)/local_pristine"
+
+test_expect_success 'setup repos for change-while-negotiating test' '
+	(
+		git init "$REPO" &&
+		cd "$REPO" &&
+		>.git/git-daemon-export-ok &&
+		test_commit m1 &&
+		git tag -d m1 &&
+
+		# Local repo with many commits (so that negotiation will take
+		# more than 1 request/response pair)
+		git clone "http://127.0.0.1:$LIB_HTTPD_PORT/smart/repo" "$LOCAL_PRISTINE" &&
+		cd "$LOCAL_PRISTINE" &&
+		git checkout -b side &&
+		for i in $(seq 1 33); do test_commit s$i; done &&
+
+		# Add novel commits to upstream
+		git checkout master &&
+		cd "$REPO" &&
+		test_commit m2 &&
+		test_commit m3 &&
+		git tag -d m2 m3
+	) &&
+	git -C "$LOCAL_PRISTINE" remote set-url origin "http://127.0.0.1:$LIB_HTTPD_PORT/one_time_sed/repo" &&
+	git -C "$LOCAL_PRISTINE" config protocol.version 2
+'
+
+inconsistency () {
+	# Simulate that the server initially reports $2 as the ref
+	# corresponding to $1, and after that, $1 as the ref corresponding to
+	# $1. This corresponds to the real-life situation where the server's
+	# repository appears to change during negotiation, for example, when
+	# different servers in a load-balancing arrangement serve (stateless)
+	# RPCs during a single negotiation.
+	printf "s/%s/%s/" \
+	       $(git -C "$REPO" rev-parse $1 | tr -d "\n") \
+	       $(git -C "$REPO" rev-parse $2 | tr -d "\n") \
+	       >"$HTTPD_ROOT_PATH/one-time-sed"
+}
+
+test_expect_success 'server is initially ahead - no ref in want' '
+	git -C "$REPO" config uploadpack.allowRefInWant false &&
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	inconsistency master 1234567890123456789012345678901234567890 &&
+	test_must_fail git -C local fetch 2>err &&
+	grep "ERR upload-pack: not our ref" err
+'
+
+test_expect_success 'server is initially ahead - ref in want' '
+	git -C "$REPO" config uploadpack.allowRefInWant true &&
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	inconsistency master 1234567890123456789012345678901234567890 &&
+	git -C local fetch &&
+
+	git -C "$REPO" rev-parse --verify master >expected &&
+	git -C local rev-parse --verify refs/remotes/origin/master >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'server is initially behind - no ref in want' '
+	git -C "$REPO" config uploadpack.allowRefInWant false &&
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	inconsistency master "master^" &&
+	git -C local fetch &&
+
+	git -C "$REPO" rev-parse --verify "master^" >expected &&
+	git -C local rev-parse --verify refs/remotes/origin/master >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'server is initially behind - ref in want' '
+	git -C "$REPO" config uploadpack.allowRefInWant true &&
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	inconsistency master "master^" &&
+	git -C local fetch &&
+
+	git -C "$REPO" rev-parse --verify "master" >expected &&
+	git -C local rev-parse --verify refs/remotes/origin/master >actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'server loses a ref - ref in want' '
+	git -C "$REPO" config uploadpack.allowRefInWant true &&
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	echo "s/master/raster/" >"$HTTPD_ROOT_PATH/one-time-sed" &&
+	test_must_fail git -C local fetch 2>err &&
+
+	grep "ERR unknown ref refs/heads/raster" err
+'
+
+stop_httpd
+
+REPO="$(pwd)/repo"
+LOCAL_PRISTINE="$(pwd)/local_pristine"
+
+# $REPO
+# c(o/foo) d(o/bar)
+#        \ /
+#         b   e(baz)  f(master)
+#          \__  |  __/
+#             \ | /
+#               a
+#
+# $LOCAL_PRISTINE
+#		s32(side)
+#		|
+#		.
+#		.
+#		|
+#		a(master)
+test_expect_success 'setup repos for fetching with ref-in-want tests' '
+	(
+		git init "$REPO" &&
+		cd "$REPO" &&
+		test_commit a &&
+
+		# Local repo with many commits (so that negotiation will take
+		# more than 1 request/response pair)
+		rm -rf "$LOCAL_PRISTINE" &&
+		git clone "file://$REPO" "$LOCAL_PRISTINE" &&
+		cd "$LOCAL_PRISTINE" &&
+		git checkout -b side &&
+		for i in $(seq 1 33); do test_commit s$i; done &&
+
+		# Add novel commits to upstream
+		git checkout master &&
+		cd "$REPO" &&
+		git checkout -b o/foo &&
+		test_commit b &&
+		test_commit c &&
+		git checkout -b o/bar b &&
+		test_commit d &&
+		git checkout -b baz a &&
+		test_commit e &&
+		git checkout master &&
+		test_commit f
+	) &&
+	git -C "$REPO" config uploadpack.allowRefInWant true &&
+	git -C "$LOCAL_PRISTINE" config protocol.version 2
+'
+
+test_expect_success 'fetching with exact OID' '
+	test_when_finished "rm -f log" &&
+
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	GIT_TRACE_PACKET="$(pwd)/log" git -C local fetch origin \
+		$(git -C "$REPO" rev-parse d):refs/heads/actual &&
+
+	git -C "$REPO" rev-parse "d" >expected &&
+	git -C local rev-parse refs/heads/actual >actual &&
+	test_cmp expected actual &&
+	grep "want $(git -C "$REPO" rev-parse d)" log
+'
+
+test_expect_success 'fetching multiple refs' '
+	test_when_finished "rm -f log" &&
+
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	GIT_TRACE_PACKET="$(pwd)/log" git -C local fetch origin master baz &&
+
+	git -C "$REPO" rev-parse "master" "baz" >expected &&
+	git -C local rev-parse refs/remotes/origin/master refs/remotes/origin/baz >actual &&
+	test_cmp expected actual &&
+	grep "want-ref refs/heads/master" log &&
+	grep "want-ref refs/heads/baz" log
+'
+
+test_expect_success 'fetching ref and exact OID' '
+	test_when_finished "rm -f log" &&
+
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	GIT_TRACE_PACKET="$(pwd)/log" git -C local fetch origin \
+		master $(git -C "$REPO" rev-parse b):refs/heads/actual &&
+
+	git -C "$REPO" rev-parse "master" "b" >expected &&
+	git -C local rev-parse refs/remotes/origin/master refs/heads/actual >actual &&
+	test_cmp expected actual &&
+	grep "want $(git -C "$REPO" rev-parse b)" log &&
+	grep "want-ref refs/heads/master" log
+'
+
+test_expect_success 'fetching with wildcard that does not match any refs' '
+	test_when_finished "rm -f log" &&
+
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	git -C local fetch origin refs/heads/none*:refs/heads/* >out &&
+	test_must_be_empty out
+'
+
+test_expect_success 'fetching with wildcard that matches multiple refs' '
+	test_when_finished "rm -f log" &&
+
+	rm -rf local &&
+	cp -r "$LOCAL_PRISTINE" local &&
+	GIT_TRACE_PACKET="$(pwd)/log" git -C local fetch origin refs/heads/o*:refs/heads/o* &&
+
+	git -C "$REPO" rev-parse "o/foo" "o/bar" >expected &&
+	git -C local rev-parse "o/foo" "o/bar" >actual &&
+	test_cmp expected actual &&
+	grep "want-ref refs/heads/o/foo" log &&
+	grep "want-ref refs/heads/o/bar" log
+'
+
+test_done

transport-helper.c

@@ -651,14 +651,16 @@ static int connect_helper(struct transport *transport, const char *name,
 }
 
 static int fetch(struct transport *transport,
-		 int nr_heads, struct ref **to_fetch)
+		 int nr_heads, struct ref **to_fetch,
+		 struct ref **fetched_refs)
 {
 	struct helper_data *data = transport->data;
 	int i, count;
 
 	if (process_connect(transport, 0)) {
 		do_take_over(transport);
-		return transport->vtable->fetch(transport, nr_heads, to_fetch);
+		return transport->vtable->fetch(transport, nr_heads, to_fetch,
+						fetched_refs);
 	}
 
 	count = 0;

transport-internal.h

@@ -36,11 +36,18 @@ struct transport_vtable {
 	 * Fetch the objects for the given refs. Note that this gets
 	 * an array, and should ignore the list structure.
 	 *
+	 * The transport *may* provide, in fetched_refs, the list of refs that
+	 * it fetched.  If the transport knows anything about the fetched refs
+	 * that the caller does not know (for example, shallow status), it
+	 * should provide that list of refs and include that information in the
+	 * list.
+	 *
 	 * If the transport did not get hashes for refs in
 	 * get_refs_list(), it should set the old_sha1 fields in the
 	 * provided refs now.
 	 **/
-	int (*fetch)(struct transport *transport, int refs_nr, struct ref **refs);
+	int (*fetch)(struct transport *transport, int refs_nr, struct ref **refs,
+		     struct ref **fetched_refs);
 
 	/**
 	 * Push the objects and refs. Send the necessary objects, and

transport.c

@@ -151,7 +151,8 @@ static struct ref *get_refs_from_bundle(struct transport *transport,
 }
 
 static int fetch_refs_from_bundle(struct transport *transport,
-			       int nr_heads, struct ref **to_fetch)
+			       int nr_heads, struct ref **to_fetch,
+			       struct ref **fetched_refs)
 {
 	struct bundle_transport_data *data = transport->data;
 	return unbundle(&data->header, data->fd,
@@ -287,7 +288,8 @@ static struct ref *get_refs_via_connect(struct transport *transport, int for_pus
 }
 
 static int fetch_refs_via_pack(struct transport *transport,
-			       int nr_heads, struct ref **to_fetch)
+			       int nr_heads, struct ref **to_fetch,
+			       struct ref **fetched_refs)
 {
 	int ret = 0;
 	struct git_transport_data *data = transport->data;
@@ -348,14 +350,19 @@ static int fetch_refs_via_pack(struct transport *transport,
 	data->got_remote_heads = 0;
 	data->options.self_contained_and_connected =
 		args.self_contained_and_connected;
+	data->options.connectivity_checked = args.connectivity_checked;
 
 	if (refs == NULL)
 		ret = -1;
 	if (report_unmatched_refs(to_fetch, nr_heads))
 		ret = -1;
 
-	free_refs(refs_tmp);
+	if (fetched_refs)
+		*fetched_refs = refs;
+	else
 		free_refs(refs);
+
+	free_refs(refs_tmp);
 	free(dest);
 	return ret;
 }
@@ -1215,19 +1222,31 @@ const struct ref *transport_get_remote_refs(struct transport *transport,
 	return transport->remote_refs;
 }
 
-int transport_fetch_refs(struct transport *transport, struct ref *refs)
+int transport_fetch_refs(struct transport *transport, struct ref *refs,
+			 struct ref **fetched_refs)
 {
 	int rc;
 	int nr_heads = 0, nr_alloc = 0, nr_refs = 0;
 	struct ref **heads = NULL;
+	struct ref *nop_head = NULL, **nop_tail = &nop_head;
 	struct ref *rm;
 
 	for (rm = refs; rm; rm = rm->next) {
 		nr_refs++;
 		if (rm->peer_ref &&
 		    !is_null_oid(&rm->old_oid) &&
-		    !oidcmp(&rm->peer_ref->old_oid, &rm->old_oid))
+		    !oidcmp(&rm->peer_ref->old_oid, &rm->old_oid)) {
+			/*
+			 * These need to be reported as fetched, but we don't
+			 * actually need to fetch them.
+			 */
+			if (fetched_refs) {
+				struct ref *nop_ref = copy_ref(rm);
+				*nop_tail = nop_ref;
+				nop_tail = &nop_ref->next;
+			}
 			continue;
+		}
 		ALLOC_GROW(heads, nr_heads + 1, nr_alloc);
 		heads[nr_heads++] = rm;
 	}
@@ -1245,7 +1264,11 @@ int transport_fetch_refs(struct transport *transport, struct ref *refs)
 			heads[nr_heads++] = rm;
 	}
 
-	rc = transport->vtable->fetch(transport, nr_heads, heads);
+	rc = transport->vtable->fetch(transport, nr_heads, heads, fetched_refs);
+	if (fetched_refs && nop_head) {
+		*nop_tail = *fetched_refs;
+		*fetched_refs = nop_head;
+	}
 
 	free(heads);
 	return rc;

transport.h

@@ -18,6 +18,17 @@ struct git_transport_options {
 	unsigned deepen_relative : 1;
 	unsigned from_promisor : 1;
 	unsigned no_dependents : 1;
+
+	/*
+	 * If this transport supports connect or stateless-connect,
+	 * the corresponding field in struct fetch_pack_args is copied
+	 * here after fetching.
+	 *
+	 * See the definition of connectivity_checked in struct
+	 * fetch_pack_args for more information.
+	 */
+	unsigned connectivity_checked:1;
+
 	int depth;
 	const char *deepen_since;
 	const struct string_list *deepen_not;
@@ -218,7 +229,8 @@ int transport_push(struct transport *connection,
 const struct ref *transport_get_remote_refs(struct transport *transport,
 					    const struct argv_array *ref_prefixes);
 
-int transport_fetch_refs(struct transport *transport, struct ref *refs);
+int transport_fetch_refs(struct transport *transport, struct ref *refs,
+			 struct ref **fetched_refs);
 void transport_unlock_pack(struct transport *transport);
 int transport_disconnect(struct transport *transport);
 char *transport_anonymize_url(const char *url);

upload-pack.c

@@ -65,6 +65,7 @@ static const char *pack_objects_hook;
 
 static int filter_capability_requested;
 static int allow_filter;
+static int allow_ref_in_want;
 static struct list_objects_filter_options filter_options;
 
 static void reset_timeout(void)
@@ -1077,6 +1078,8 @@ static int upload_pack_config(const char *var, const char *value, void *unused)
 			return git_config_string(&pack_objects_hook, var, value);
 	} else if (!strcmp("uploadpack.allowfilter", var)) {
 		allow_filter = git_config_bool(var, value);
+	} else if (!strcmp("uploadpack.allowrefinwant", var)) {
+		allow_ref_in_want = git_config_bool(var, value);
 	}
 	return parse_hide_refs_config(var, value, "uploadpack");
 }
@@ -1116,6 +1119,7 @@ void upload_pack(struct upload_pack_options *options)
 
 struct upload_pack_data {
 	struct object_array wants;
+	struct string_list wanted_refs;
 	struct oid_array haves;
 
 	struct object_array shallows;
@@ -1137,12 +1141,14 @@ struct upload_pack_data {
 static void upload_pack_data_init(struct upload_pack_data *data)
 {
 	struct object_array wants = OBJECT_ARRAY_INIT;
+	struct string_list wanted_refs = STRING_LIST_INIT_DUP;
 	struct oid_array haves = OID_ARRAY_INIT;
 	struct object_array shallows = OBJECT_ARRAY_INIT;
 	struct string_list deepen_not = STRING_LIST_INIT_DUP;
 
 	memset(data, 0, sizeof(*data));
 	data->wants = wants;
+	data->wanted_refs = wanted_refs;
 	data->haves = haves;
 	data->shallows = shallows;
 	data->deepen_not = deepen_not;
@@ -1151,6 +1157,7 @@ static void upload_pack_data_init(struct upload_pack_data *data)
 static void upload_pack_data_clear(struct upload_pack_data *data)
 {
 	object_array_clear(&data->wants);
+	string_list_clear(&data->wanted_refs, 1);
 	oid_array_clear(&data->haves);
 	object_array_clear(&data->shallows);
 	string_list_clear(&data->deepen_not, 0);
@@ -1187,6 +1194,34 @@ static int parse_want(const char *line)
 	return 0;
 }
 
+static int parse_want_ref(const char *line, struct string_list *wanted_refs)
+{
+	const char *arg;
+	if (skip_prefix(line, "want-ref ", &arg)) {
+		struct object_id oid;
+		struct string_list_item *item;
+		struct object *o;
+
+		if (read_ref(arg, &oid)) {
+			packet_write_fmt(1, "ERR unknown ref %s", arg);
+			die("unknown ref %s", arg);
+		}
+
+		item = string_list_append(wanted_refs, arg);
+		item->util = oiddup(&oid);
+
+		o = parse_object_or_die(&oid, arg);
+		if (!(o->flags & WANTED)) {
+			o->flags |= WANTED;
+			add_object_array(o, NULL, &want_obj);
+		}
+
+		return 1;
+	}
+
+	return 0;
+}
+
 static int parse_have(const char *line, struct oid_array *haves)
 {
 	const char *arg;
@@ -1212,6 +1247,8 @@ static void process_args(struct packet_reader *request,
 		/* process want */
 		if (parse_want(arg))
 			continue;
+		if (allow_ref_in_want && parse_want_ref(arg, &data->wanted_refs))
+			continue;
 		/* process have line */
 		if (parse_have(arg, &data->haves))
 			continue;
@@ -1354,6 +1391,24 @@ static int process_haves_and_send_acks(struct upload_pack_data *data)
 	return ret;
 }
 
+static void send_wanted_ref_info(struct upload_pack_data *data)
+{
+	const struct string_list_item *item;
+
+	if (!data->wanted_refs.nr)
+		return;
+
+	packet_write_fmt(1, "wanted-refs\n");
+
+	for_each_string_list_item(item, &data->wanted_refs) {
+		packet_write_fmt(1, "%s %s\n",
+				 oid_to_hex(item->util),
+				 item->string);
+	}
+
+	packet_delim(1);
+}
+
 static void send_shallow_info(struct upload_pack_data *data)
 {
 	/* No shallow info needs to be sent */
@@ -1421,6 +1476,7 @@ int upload_pack_v2(struct repository *r, struct argv_array *keys,
 				state = FETCH_DONE;
 			break;
 		case FETCH_SEND_PACK:
+			send_wanted_ref_info(&data);
 			send_shallow_info(&data);
 
 			packet_write_fmt(1, "packfile\n");
@@ -1441,12 +1497,22 @@ int upload_pack_advertise(struct repository *r,
 {
 	if (value) {
 		int allow_filter_value;
+		int allow_ref_in_want;
+
 		strbuf_addstr(value, "shallow");
+
 		if (!repo_config_get_bool(the_repository,
 					 "uploadpack.allowfilter",
 					 &allow_filter_value) &&
 		    allow_filter_value)
 			strbuf_addstr(value, " filter");
+
+		if (!repo_config_get_bool(the_repository,
+					 "uploadpack.allowrefinwant",
+					 &allow_ref_in_want) &&
+		    allow_ref_in_want)
+			strbuf_addstr(value, " ref-in-want");
 	}
+
 	return 1;
 }