merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 386 insertions, 188 deletions

diff --git a/third_party/git/fetch-pack.c b/third_party/git/fetch-pack.c
index 65be043f2a..b10c432315 100644
--- a/third_party/git/fetch-pack.c
+++ b/third_party/git/fetch-pack.c
@@ -15,13 +15,14 @@
 #include "connect.h"
 #include "transport.h"
 #include "version.h"
-#include "sha1-array.h"
+#include "oid-array.h"
 #include "oidset.h"
 #include "packfile.h"
 #include "object-store.h"
 #include "connected.h"
 #include "fetch-negotiator.h"
 #include "fsck.h"
+#include "shallow.h"
 
 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
@@ -34,10 +35,10 @@ static int fetch_fsck_objects = -1;
 static int transfer_fsck_objects = -1;
 static int agent_supported;
 static int server_supports_filtering;
-static struct lock_file shallow_lock;
+static struct shallow_lock shallow_lock;
 static const char *alternate_shallow_file;
-static char *negotiation_algorithm;
 static struct strbuf fsck_msg_types = STRBUF_INIT;
+static struct string_list uri_protocols = STRING_LIST_INIT_DUP;
 
 /* Remember to update object flag allocation in object.h */
 #define COMPLETE	(1U << 0)
@@ -107,24 +108,48 @@ static void for_each_cached_alternate(struct fetch_negotiator *negotiator,
 		cb(negotiator, cache.items[i]);
 }
 
+static struct commit *deref_without_lazy_fetch(const struct object_id *oid,
+					       int mark_tags_complete)
+{
+	enum object_type type;
+	struct object_info info = { .typep = &type };
+
+	while (1) {
+		if (oid_object_info_extended(the_repository, oid, &info,
+					     OBJECT_INFO_SKIP_FETCH_OBJECT | OBJECT_INFO_QUICK))
+			return NULL;
+		if (type == OBJ_TAG) {
+			struct tag *tag = (struct tag *)
+				parse_object(the_repository, oid);
+
+			if (!tag->tagged)
+				return NULL;
+			if (mark_tags_complete)
+				tag->object.flags |= COMPLETE;
+			oid = &tag->tagged->oid;
+		} else {
+			break;
+		}
+	}
+	if (type == OBJ_COMMIT)
+		return (struct commit *) parse_object(the_repository, oid);
+	return NULL;
+}
+
 static int rev_list_insert_ref(struct fetch_negotiator *negotiator,
-			       const char *refname,
 			       const struct object_id *oid)
 {
-	struct object *o = deref_tag(the_repository,
-				     parse_object(the_repository, oid),
-				     refname, 0);
-
-	if (o && o->type == OBJ_COMMIT)
-		negotiator->add_tip(negotiator, (struct commit *)o);
+	struct commit *c = deref_without_lazy_fetch(oid, 0);
 
+	if (c)
+		negotiator->add_tip(negotiator, c);
 	return 0;
 }
 
 static int rev_list_insert_ref_oid(const char *refname, const struct object_id *oid,
 				   int flag, void *cb_data)
 {
-	return rev_list_insert_ref(cb_data, refname, oid);
+	return rev_list_insert_ref(cb_data, oid);
 }
 
 enum ack_type {
@@ -168,16 +193,16 @@ static enum ack_type get_ack(struct packet_reader *reader,
 	if (!strcmp(reader->line, "NAK"))
 		return NAK;
 	if (skip_prefix(reader->line, "ACK ", &arg)) {
-		if (!get_oid_hex(arg, result_oid)) {
-			arg += 40;
-			len -= arg - reader->line;
+		const char *p;
+		if (!parse_oid_hex(arg, result_oid, &p)) {
+			len -= p - reader->line;
 			if (len < 1)
 				return ACK;
-			if (strstr(arg, "continue"))
+			if (strstr(p, "continue"))
 				return ACK_continue;
-			if (strstr(arg, "common"))
+			if (strstr(p, "common"))
 				return ACK_common;
-			if (strstr(arg, "ready"))
+			if (strstr(p, "ready"))
 				return ACK_ready;
 			return ACK;
 		}
@@ -200,7 +225,7 @@ static void send_request(struct fetch_pack_args *args,
 static void insert_one_alternate_object(struct fetch_negotiator *negotiator,
 					struct object *obj)
 {
-	rev_list_insert_ref(negotiator, NULL, &obj->oid);
+	rev_list_insert_ref(negotiator, &obj->oid);
 }
 
 #define INITIAL_FLUSH 16
@@ -229,13 +254,12 @@ static void mark_tips(struct fetch_negotiator *negotiator,
 	int i;
 
 	if (!negotiation_tips) {
-		for_each_ref(rev_list_insert_ref_oid, negotiator);
+		for_each_rawref(rev_list_insert_ref_oid, negotiator);
 		return;
 	}
 
 	for (i = 0; i < negotiation_tips->nr; i++)
-		rev_list_insert_ref(negotiator, NULL,
-				    &negotiation_tips->oid[i]);
+		rev_list_insert_ref(negotiator, &negotiation_tips->oid[i]);
 	return;
 }
 
@@ -261,10 +285,8 @@ static int find_common(struct fetch_negotiator *negotiator,
 			   PACKET_READ_CHOMP_NEWLINE |
 			   PACKET_READ_DIE_ON_ERR_PACKET);
 
-	if (!args->no_dependents) {
-		mark_tips(negotiator, args->negotiation_tips);
-		for_each_cached_alternate(negotiator, insert_one_alternate_object);
-	}
+	mark_tips(negotiator, args->negotiation_tips);
+	for_each_cached_alternate(negotiator, insert_one_alternate_object);
 
 	fetching = 0;
 	for ( ; refs ; refs = refs->next) {
@@ -281,12 +303,8 @@ static int find_common(struct fetch_negotiator *negotiator,
 		 * We use lookup_object here because we are only
 		 * interested in the case we *know* the object is
 		 * reachable and we have already scanned it.
-		 *
-		 * Do this only if args->no_dependents is false (if it is true,
-		 * we cannot trust the object flags).
 		 */
-		if (!args->no_dependents &&
-		    ((o = lookup_object(the_repository, remote)) != NULL) &&
+		if (((o = lookup_object(the_repository, remote)) != NULL) &&
 				(o->flags & COMPLETE)) {
 			continue;
 		}
@@ -339,12 +357,9 @@ static int find_common(struct fetch_negotiator *negotiator,
 		}
 	}
 	if (server_supports_filtering && args->filter_options.choice) {
-		struct strbuf expanded_filter_spec = STRBUF_INIT;
-		expand_list_objects_filter_spec(&args->filter_options,
-						&expanded_filter_spec);
-		packet_buf_write(&req_buf, "filter %s",
-				 expanded_filter_spec.buf);
-		strbuf_release(&expanded_filter_spec);
+		const char *spec =
+			expand_list_objects_filter_spec(&args->filter_options);
+		packet_buf_write(&req_buf, "filter %s", spec);
 	}
 	packet_buf_flush(&req_buf);
 	state_len = req_buf.len;
@@ -386,10 +401,9 @@ static int find_common(struct fetch_negotiator *negotiator,
 		state_len = 0;
 	}
 
+	trace2_region_enter("fetch-pack", "negotiation_v0_v1", the_repository);
 	flushes = 0;
 	retval = -1;
-	if (args->no_dependents)
-		goto done;
 	while ((oid = negotiator->next(negotiator))) {
 		packet_buf_write(&req_buf, "have %s\n", oid_to_hex(oid));
 		print_verbose(args, "have %s", oid_to_hex(oid));
@@ -470,6 +484,7 @@ static int find_common(struct fetch_negotiator *negotiator,
 		}
 	}
 done:
+	trace2_region_leave("fetch-pack", "negotiation_v0_v1", the_repository);
 	if (!got_ready || !no_done) {
 		packet_buf_write(&req_buf, "done\n");
 		send_request(args, fd[1], &req_buf);
@@ -503,21 +518,11 @@ static struct commit_list *complete;
 
 static int mark_complete(const struct object_id *oid)
 {
-	struct object *o = parse_object(the_repository, oid);
-
-	while (o && o->type == OBJ_TAG) {
-		struct tag *t = (struct tag *) o;
-		if (!t->tagged)
-			break; /* broken repository */
-		o->flags |= COMPLETE;
-		o = parse_object(the_repository, &t->tagged->oid);
-	}
-	if (o && o->type == OBJ_COMMIT) {
-		struct commit *commit = (struct commit *)o;
-		if (!(commit->object.flags & COMPLETE)) {
-			commit->object.flags |= COMPLETE;
-			commit_list_insert(commit, &complete);
-		}
+	struct commit *commit = deref_without_lazy_fetch(oid, 1);
+
+	if (commit && !(commit->object.flags & COMPLETE)) {
+		commit->object.flags |= COMPLETE;
+		commit_list_insert(commit, &complete);
 	}
 	return 0;
 }
@@ -653,9 +658,7 @@ struct loose_object_iter {
 
 /*
  * Mark recent commits available locally and reachable from a local ref as
- * COMPLETE. If args->no_dependents is false, also mark COMPLETE remote refs as
- * COMMON_REF (otherwise, we are not planning to participate in negotiation, and
- * thus do not need COMMON_REF marks).
+ * COMPLETE.
  *
  * The cutoff time for recency is determined by this heuristic: it is the
  * earliest commit time of the objects in refs that are commits and that we know
@@ -671,17 +674,20 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 
 	save_commit_buffer = 0;
 
+	trace2_region_enter("fetch-pack", "parse_remote_refs_and_find_cutoff", NULL);
 	for (ref = *refs; ref; ref = ref->next) {
 		struct object *o;
 
 		if (!has_object_file_with_flags(&ref->old_oid,
-						OBJECT_INFO_QUICK))
+						OBJECT_INFO_QUICK |
+							OBJECT_INFO_SKIP_FETCH_OBJECT))
 			continue;
 		o = parse_object(the_repository, &ref->old_oid);
 		if (!o)
 			continue;
 
-		/* We already have it -- which may mean that we were
+		/*
+		 * We already have it -- which may mean that we were
 		 * in sync with the other side at some time after
 		 * that (it is OK if we guess wrong here).
 		 */
@@ -691,31 +697,36 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 				cutoff = commit->date;
 		}
 	}
+	trace2_region_leave("fetch-pack", "parse_remote_refs_and_find_cutoff", NULL);
 
+	/*
+	 * This block marks all local refs as COMPLETE, and then recursively marks all
+	 * parents of those refs as COMPLETE.
+	 */
+	trace2_region_enter("fetch-pack", "mark_complete_local_refs", NULL);
 	if (!args->deepen) {
-		for_each_ref(mark_complete_oid, NULL);
+		for_each_rawref(mark_complete_oid, NULL);
 		for_each_cached_alternate(NULL, mark_alternate_complete);
 		commit_list_sort_by_date(&complete);
 		if (cutoff)
 			mark_recent_complete_commits(args, cutoff);
 	}
+	trace2_region_leave("fetch-pack", "mark_complete_local_refs", NULL);
 
 	/*
 	 * Mark all complete remote refs as common refs.
 	 * Don't mark them common yet; the server has to be told so first.
 	 */
+	trace2_region_enter("fetch-pack", "mark_common_remote_refs", NULL);
 	for (ref = *refs; ref; ref = ref->next) {
-		struct object *o = deref_tag(the_repository,
-					     lookup_object(the_repository,
-					     &ref->old_oid),
-					     NULL, 0);
+		struct commit *c = deref_without_lazy_fetch(&ref->old_oid, 0);
 
-		if (!o || o->type != OBJ_COMMIT || !(o->flags & COMPLETE))
+		if (!c || !(c->object.flags & COMPLETE))
 			continue;
 
-		negotiator->known_common(negotiator,
-					 (struct commit *)o);
+		negotiator->known_common(negotiator, c);
 	}
+	trace2_region_leave("fetch-pack", "mark_common_remote_refs", NULL);
 
 	save_commit_buffer = old_save_commit_buffer;
 }
@@ -758,8 +769,38 @@ static int sideband_demux(int in, int out, void *data)
 	return ret;
 }
 
+static void write_promisor_file(const char *keep_name,
+				struct ref **sought, int nr_sought)
+{
+	struct strbuf promisor_name = STRBUF_INIT;
+	int suffix_stripped;
+	FILE *output;
+	int i;
+
+	strbuf_addstr(&promisor_name, keep_name);
+	suffix_stripped = strbuf_strip_suffix(&promisor_name, ".keep");
+	if (!suffix_stripped)
+		BUG("name of pack lockfile should end with .keep (was '%s')",
+		    keep_name);
+	strbuf_addstr(&promisor_name, ".promisor");
+
+	output = xfopen(promisor_name.buf, "w");
+	for (i = 0; i < nr_sought; i++)
+		fprintf(output, "%s %s\n", oid_to_hex(&sought[i]->old_oid),
+			sought[i]->name);
+	fclose(output);
+
+	strbuf_release(&promisor_name);
+}
+
+/*
+ * Pass 1 as "only_packfile" if the pack received is the only pack in this
+ * fetch request (that is, if there were no packfile URIs provided).
+ */
 static int get_pack(struct fetch_pack_args *args,
-		    int xd[2], char **pack_lockfile)
+		    int xd[2], struct string_list *pack_lockfiles,
+		    int only_packfile,
+		    struct ref **sought, int nr_sought)
 {
 	struct async demux;
 	int do_keep = args->keep_pack;
@@ -797,68 +838,85 @@ static int get_pack(struct fetch_pack_args *args,
 	}
 
 	if (alternate_shallow_file) {
-		argv_array_push(&cmd.args, "--shallow-file");
-		argv_array_push(&cmd.args, alternate_shallow_file);
+		strvec_push(&cmd.args, "--shallow-file");
+		strvec_push(&cmd.args, alternate_shallow_file);
 	}
 
 	if (do_keep || args->from_promisor) {
-		if (pack_lockfile)
+		if (pack_lockfiles)
 			cmd.out = -1;
 		cmd_name = "index-pack";
-		argv_array_push(&cmd.args, cmd_name);
-		argv_array_push(&cmd.args, "--stdin");
+		strvec_push(&cmd.args, cmd_name);
+		strvec_push(&cmd.args, "--stdin");
 		if (!args->quiet && !args->no_progress)
-			argv_array_push(&cmd.args, "-v");
+			strvec_push(&cmd.args, "-v");
 		if (args->use_thin_pack)
-			argv_array_push(&cmd.args, "--fix-thin");
+			strvec_push(&cmd.args, "--fix-thin");
 		if (do_keep && (args->lock_pack || unpack_limit)) {
 			char hostname[HOST_NAME_MAX + 1];
 			if (xgethostname(hostname, sizeof(hostname)))
 				xsnprintf(hostname, sizeof(hostname), "localhost");
-			argv_array_pushf(&cmd.args,
-					"--keep=fetch-pack %"PRIuMAX " on %s",
-					(uintmax_t)getpid(), hostname);
+			strvec_pushf(&cmd.args,
+				     "--keep=fetch-pack %"PRIuMAX " on %s",
+				     (uintmax_t)getpid(), hostname);
 		}
-		if (args->check_self_contained_and_connected)
-			argv_array_push(&cmd.args, "--check-self-contained-and-connected");
+		if (only_packfile && args->check_self_contained_and_connected)
+			strvec_push(&cmd.args, "--check-self-contained-and-connected");
+		else
+			/*
+			 * We cannot perform any connectivity checks because
+			 * not all packs have been downloaded; let the caller
+			 * have this responsibility.
+			 */
+			args->check_self_contained_and_connected = 0;
+
 		if (args->from_promisor)
-			argv_array_push(&cmd.args, "--promisor");
+			/*
+			 * write_promisor_file() may be called afterwards but
+			 * we still need index-pack to know that this is a
+			 * promisor pack. For example, if transfer.fsckobjects
+			 * is true, index-pack needs to know that .gitmodules
+			 * is a promisor object (so that it won't complain if
+			 * it is missing).
+			 */
+			strvec_push(&cmd.args, "--promisor");
 	}
 	else {
 		cmd_name = "unpack-objects";
-		argv_array_push(&cmd.args, cmd_name);
+		strvec_push(&cmd.args, cmd_name);
 		if (args->quiet || args->no_progress)
-			argv_array_push(&cmd.args, "-q");
+			strvec_push(&cmd.args, "-q");
 		args->check_self_contained_and_connected = 0;
 	}
 
 	if (pass_header)
-		argv_array_pushf(&cmd.args, "--pack_header=%"PRIu32",%"PRIu32,
-				 ntohl(header.hdr_version),
+		strvec_pushf(&cmd.args, "--pack_header=%"PRIu32",%"PRIu32,
+			     ntohl(header.hdr_version),
 				 ntohl(header.hdr_entries));
 	if (fetch_fsck_objects >= 0
 	    ? fetch_fsck_objects
 	    : transfer_fsck_objects >= 0
 	    ? transfer_fsck_objects
 	    : 0) {
-		if (args->from_promisor)
+		if (args->from_promisor || !only_packfile)
 			/*
 			 * We cannot use --strict in index-pack because it
 			 * checks both broken objects and links, but we only
 			 * want to check for broken objects.
 			 */
-			argv_array_push(&cmd.args, "--fsck-objects");
+			strvec_push(&cmd.args, "--fsck-objects");
 		else
-			argv_array_pushf(&cmd.args, "--strict%s",
-					 fsck_msg_types.buf);
+			strvec_pushf(&cmd.args, "--strict%s",
+				     fsck_msg_types.buf);
 	}
 
 	cmd.in = demux.out;
 	cmd.git_cmd = 1;
 	if (start_command(&cmd))
 		die(_("fetch-pack: unable to fork off %s"), cmd_name);
-	if (do_keep && pack_lockfile) {
-		*pack_lockfile = index_pack_lockfile(cmd.out);
+	if (do_keep && pack_lockfiles) {
+		string_list_append_nodup(pack_lockfiles,
+					 index_pack_lockfile(cmd.out));
 		close(cmd.out);
 	}
 
@@ -875,6 +933,14 @@ static int get_pack(struct fetch_pack_args *args,
 		die(_("%s failed"), cmd_name);
 	if (use_sideband && finish_async(&demux))
 		die(_("error in sideband demultiplexer"));
+
+	/*
+	 * Now that index-pack has succeeded, write the promisor file using the
+	 * obtained .keep filename if necessary
+	 */
+	if (do_keep && pack_lockfiles && pack_lockfiles->nr && args->from_promisor)
+		write_promisor_file(pack_lockfiles->items[0].string, sought, nr_sought);
+
 	return 0;
 }
 
@@ -890,14 +956,18 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 				 const struct ref *orig_ref,
 				 struct ref **sought, int nr_sought,
 				 struct shallow_info *si,
-				 char **pack_lockfile)
+				 struct string_list *pack_lockfiles)
 {
+	struct repository *r = the_repository;
 	struct ref *ref = copy_ref_list(orig_ref);
 	struct object_id oid;
 	const char *agent_feature;
 	int agent_len;
-	struct fetch_negotiator negotiator;
-	fetch_negotiator_init(&negotiator, negotiation_algorithm);
+	struct fetch_negotiator negotiator_alloc;
+	struct fetch_negotiator *negotiator;
+
+	negotiator = &negotiator_alloc;
+	fetch_negotiator_init(r, negotiator);
 
 	sort_ref_list(&ref, ref_compare_name);
 	QSORT(sought, nr_sought, cmp_ref_by_name);
@@ -911,7 +981,7 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 
 	if (server_supports("shallow"))
 		print_verbose(args, _("Server supports %s"), "shallow");
-	else if (args->depth > 0 || is_repository_shallow(the_repository))
+	else if (args->depth > 0 || is_repository_shallow(r))
 		die(_("Server does not support shallow clients"));
 	if (args->depth > 0 || args->deepen_since || args->deepen_not)
 		args->deepen = 1;
@@ -982,18 +1052,16 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 		print_verbose(args, _("Server supports %s"), "deepen-relative");
 	else if (args->deepen_relative)
 		die(_("Server does not support --deepen"));
+	if (!server_supports_hash(the_hash_algo->name, NULL))
+		die(_("Server does not support this repository's object format"));
 
-	if (!args->no_dependents) {
-		mark_complete_and_common_ref(&negotiator, args, &ref);
-		filter_refs(args, &ref, sought, nr_sought);
-		if (everything_local(args, &ref)) {
-			packet_flush(fd[1]);
-			goto all_done;
-		}
-	} else {
-		filter_refs(args, &ref, sought, nr_sought);
+	mark_complete_and_common_ref(negotiator, args, &ref);
+	filter_refs(args, &ref, sought, nr_sought);
+	if (everything_local(args, &ref)) {
+		packet_flush(fd[1]);
+		goto all_done;
 	}
-	if (find_common(&negotiator, args, fd, &oid, ref) < 0)
+	if (find_common(negotiator, args, fd, &oid, ref) < 0)
 		if (!args->keep_pack)
 			/* When cloning, it is not unusual to have
 			 * no common commit.
@@ -1009,11 +1077,12 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 		alternate_shallow_file = setup_temporary_shallow(si->shallow);
 	else
 		alternate_shallow_file = NULL;
-	if (get_pack(args, fd, pack_lockfile))
+	if (get_pack(args, fd, pack_lockfiles, 1, sought, nr_sought))
 		die(_("git fetch-pack: fetch failed."));
 
  all_done:
-	negotiator.release(&negotiator);
+	if (negotiator)
+		negotiator->release(negotiator);
 	return ref;
 }
 
@@ -1039,7 +1108,7 @@ static void add_shallow_requests(struct strbuf *req_buf,
 		packet_buf_write(req_buf, "deepen-relative\n");
 }
 
-static void add_wants(int no_dependents, const struct ref *wants, 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);
 
@@ -1056,12 +1125,8 @@ static void add_wants(int no_dependents, const struct ref *wants, struct strbuf
 		 * We use lookup_object here because we are only
 		 * interested in the case we *know* the object is
 		 * reachable and we have already scanned it.
-		 *
-		 * Do this only if args->no_dependents is false (if it is true,
-		 * we cannot trust the object flags).
 		 */
-		if (!no_dependents &&
-		    ((o = lookup_object(the_repository, remote)) != NULL) &&
+		if (((o = lookup_object(the_repository, remote)) != NULL) &&
 		    (o->flags & COMPLETE)) {
 			continue;
 		}
@@ -1085,6 +1150,7 @@ static void add_common(struct strbuf *req_buf, struct oidset *common)
 }
 
 static int add_haves(struct fetch_negotiator *negotiator,
+		     int seen_ack,
 		     struct strbuf *req_buf,
 		     int *haves_to_send, int *in_vain)
 {
@@ -1099,7 +1165,7 @@ static int add_haves(struct fetch_negotiator *negotiator,
 	}
 
 	*in_vain += haves_added;
-	if (!haves_added || *in_vain >= MAX_IN_VAIN) {
+	if (!haves_added || (seen_ack && *in_vain >= MAX_IN_VAIN)) {
 		/* Send Done */
 		packet_buf_write(req_buf, "done\n");
 		ret = 1;
@@ -1112,12 +1178,13 @@ static int add_haves(struct fetch_negotiator *negotiator,
 }
 
 static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
-			      const struct fetch_pack_args *args,
+			      struct fetch_pack_args *args,
 			      const struct ref *wants, struct oidset *common,
 			      int *haves_to_send, int *in_vain,
-			      int sideband_all)
+			      int sideband_all, int seen_ack)
 {
 	int ret = 0;
+	const char *hash_name;
 	struct strbuf req_buf = STRBUF_INIT;
 
 	if (server_supports_v2("fetch", 1))
@@ -1132,6 +1199,17 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 					 args->server_options->items[i].string);
 	}
 
+	if (server_feature_v2("object-format", &hash_name)) {
+		int hash_algo = hash_algo_by_name(hash_name);
+		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
+			die(_("mismatched algorithms: client %s; server %s"),
+			    the_hash_algo->name, hash_name);
+		packet_write_fmt(fd_out, "object-format=%s", the_hash_algo->name);
+	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1) {
+		die(_("the server does not support algorithm '%s'"),
+		    the_hash_algo->name);
+	}
+
 	packet_buf_delim(&req_buf);
 	if (args->use_thin_pack)
 		packet_buf_write(&req_buf, "thin-pack");
@@ -1153,31 +1231,44 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	/* Add filter */
 	if (server_supports_feature("fetch", "filter", 0) &&
 	    args->filter_options.choice) {
-		struct strbuf expanded_filter_spec = STRBUF_INIT;
+		const char *spec =
+			expand_list_objects_filter_spec(&args->filter_options);
 		print_verbose(args, _("Server supports filter"));
-		expand_list_objects_filter_spec(&args->filter_options,
-						&expanded_filter_spec);
-		packet_buf_write(&req_buf, "filter %s",
-				 expanded_filter_spec.buf);
-		strbuf_release(&expanded_filter_spec);
+		packet_buf_write(&req_buf, "filter %s", spec);
 	} else if (args->filter_options.choice) {
 		warning("filtering not recognized by server, ignoring");
 	}
 
-	/* add wants */
-	add_wants(args->no_dependents, wants, &req_buf);
+	if (server_supports_feature("fetch", "packfile-uris", 0)) {
+		int i;
+		struct strbuf to_send = STRBUF_INIT;
 
-	if (args->no_dependents) {
-		packet_buf_write(&req_buf, "done");
-		ret = 1;
-	} else {
-		/* Add all of the common commits we've found in previous rounds */
-		add_common(&req_buf, common);
+		for (i = 0; i < uri_protocols.nr; i++) {
+			const char *s = uri_protocols.items[i].string;
 
-		/* Add initial haves */
-		ret = add_haves(negotiator, &req_buf, haves_to_send, in_vain);
+			if (!strcmp(s, "https") || !strcmp(s, "http")) {
+				if (to_send.len)
+					strbuf_addch(&to_send, ',');
+				strbuf_addstr(&to_send, s);
+			}
+		}
+		if (to_send.len) {
+			packet_buf_write(&req_buf, "packfile-uris %s",
+					 to_send.buf);
+			strbuf_release(&to_send);
+		}
 	}
 
+	/* add wants */
+	add_wants(wants, &req_buf);
+
+	/* Add all of the common commits we've found in previous rounds */
+	add_common(&req_buf, common);
+
+	/* Add initial haves */
+	ret = add_haves(negotiator, seen_ack, &req_buf,
+			haves_to_send, in_vain);
+
 	/* Send request */
 	packet_buf_flush(&req_buf);
 	if (write_in_full(fd_out, req_buf.buf, req_buf.len) < 0)
@@ -1213,9 +1304,29 @@ static int process_section_header(struct packet_reader *reader,
 	return ret;
 }
 
-static int process_acks(struct fetch_negotiator *negotiator,
-			struct packet_reader *reader,
-			struct oidset *common)
+enum common_found {
+	/*
+	 * No commit was found to be possessed by both the client and the
+	 * server, and "ready" was not received.
+	 */
+	NO_COMMON_FOUND,
+
+	/*
+	 * At least one commit was found to be possessed by both the client and
+	 * the server, and "ready" was not received.
+	 */
+	COMMON_FOUND,
+
+	/*
+	 * "ready" was received, indicating that the server is ready to send
+	 * the packfile without any further negotiation.
+	 */
+	READY
+};
+
+static enum common_found process_acks(struct fetch_negotiator *negotiator,
+				      struct packet_reader *reader,
+				      struct oidset *common)
 {
 	/* received */
 	int received_ready = 0;
@@ -1230,11 +1341,13 @@ static int process_acks(struct fetch_negotiator *negotiator,
 
 		if (skip_prefix(reader->line, "ACK ", &arg)) {
 			struct object_id oid;
+			received_ack = 1;
 			if (!get_oid_hex(arg, &oid)) {
 				struct commit *commit;
 				oidset_insert(common, &oid);
 				commit = lookup_commit(the_repository, &oid);
-				negotiator->ack(negotiator, commit);
+				if (negotiator)
+					negotiator->ack(negotiator, commit);
 			}
 			continue;
 		}
@@ -1263,8 +1376,8 @@ static int process_acks(struct fetch_negotiator *negotiator,
 	if (!received_ready && reader->status != PACKET_READ_FLUSH)
 		die(_("expected no other sections to be sent after no 'ready'"));
 
-	/* return 0 if no common, 1 if there are common, or 2 if ready */
-	return received_ready ? 2 : (received_ack ? 1 : 0);
+	return received_ready ? READY :
+		(received_ack ? COMMON_FOUND : NO_COMMON_FOUND);
 }
 
 static void receive_shallow_info(struct fetch_pack_args *args,
@@ -1363,6 +1476,21 @@ static void receive_wanted_refs(struct packet_reader *reader,
 		die(_("error processing wanted refs: %d"), reader->status);
 }
 
+static void receive_packfile_uris(struct packet_reader *reader,
+				  struct string_list *uris)
+{
+	process_section_header(reader, "packfile-uris", 0);
+	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
+		if (reader->pktlen < the_hash_algo->hexsz ||
+		    reader->line[the_hash_algo->hexsz] != ' ')
+			die("expected '<hash> <uri>', got: %s\n", reader->line);
+
+		string_list_append(uris, reader->line);
+	}
+	if (reader->status != PACKET_READ_DELIM)
+		die("expected DELIM");
+}
+
 enum fetch_state {
 	FETCH_CHECK_LOCAL = 0,
 	FETCH_SEND_REQUEST,
@@ -1371,22 +1499,37 @@ enum fetch_state {
 	FETCH_DONE,
 };
 
+static void do_check_stateless_delimiter(const struct fetch_pack_args *args,
+					 struct packet_reader *reader)
+{
+	check_stateless_delimiter(args->stateless_rpc, reader,
+				  _("git fetch-pack: expected response end packet"));
+}
+
 static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				    int fd[2],
 				    const struct ref *orig_ref,
 				    struct ref **sought, int nr_sought,
 				    struct oid_array *shallows,
 				    struct shallow_info *si,
-				    char **pack_lockfile)
+				    struct string_list *pack_lockfiles)
 {
+	struct repository *r = the_repository;
 	struct ref *ref = copy_ref_list(orig_ref);
 	enum fetch_state state = FETCH_CHECK_LOCAL;
 	struct oidset common = OIDSET_INIT;
 	struct packet_reader reader;
-	int in_vain = 0;
+	int in_vain = 0, negotiation_started = 0;
 	int haves_to_send = INITIAL_FLUSH;
-	struct fetch_negotiator negotiator;
-	fetch_negotiator_init(&negotiator, negotiation_algorithm);
+	struct fetch_negotiator negotiator_alloc;
+	struct fetch_negotiator *negotiator;
+	int seen_ack = 0;
+	struct string_list packfile_uris = STRING_LIST_INIT_DUP;
+	int i;
+
+	negotiator = &negotiator_alloc;
+	fetch_negotiator_init(r, negotiator);
+
 	packet_reader_init(&reader, fd[0], NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
 			   PACKET_READ_DIE_ON_ERR_PACKET);
@@ -1409,46 +1552,57 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 				args->deepen = 1;
 
 			/* Filter 'ref' by 'sought' and those that aren't local */
-			if (!args->no_dependents) {
-				mark_complete_and_common_ref(&negotiator, args, &ref);
-				filter_refs(args, &ref, sought, nr_sought);
-				if (everything_local(args, &ref))
-					state = FETCH_DONE;
-				else
-					state = FETCH_SEND_REQUEST;
-
-				mark_tips(&negotiator, args->negotiation_tips);
-				for_each_cached_alternate(&negotiator,
-							  insert_one_alternate_object);
-			} else {
-				filter_refs(args, &ref, sought, nr_sought);
+			mark_complete_and_common_ref(negotiator, args, &ref);
+			filter_refs(args, &ref, sought, nr_sought);
+			if (everything_local(args, &ref))
+				state = FETCH_DONE;
+			else
 				state = FETCH_SEND_REQUEST;
-			}
+
+			mark_tips(negotiator, args->negotiation_tips);
+			for_each_cached_alternate(negotiator,
+						  insert_one_alternate_object);
 			break;
 		case FETCH_SEND_REQUEST:
-			if (send_fetch_request(&negotiator, fd[1], args, ref,
+			if (!negotiation_started) {
+				negotiation_started = 1;
+				trace2_region_enter("fetch-pack",
+						    "negotiation_v2",
+						    the_repository);
+			}
+			if (send_fetch_request(negotiator, fd[1], args, ref,
 					       &common,
 					       &haves_to_send, &in_vain,
-					       reader.use_sideband))
+					       reader.use_sideband,
+					       seen_ack))
 				state = FETCH_GET_PACK;
 			else
 				state = FETCH_PROCESS_ACKS;
 			break;
 		case FETCH_PROCESS_ACKS:
 			/* Process ACKs/NAKs */
-			switch (process_acks(&negotiator, &reader, &common)) {
-			case 2:
+			switch (process_acks(negotiator, &reader, &common)) {
+			case READY:
+				/*
+				 * Don't check for response delimiter; get_pack() will
+				 * read the rest of this response.
+				 */
 				state = FETCH_GET_PACK;
 				break;
-			case 1:
+			case COMMON_FOUND:
 				in_vain = 0;
+				seen_ack = 1;
 				/* fallthrough */
-			default:
+			case NO_COMMON_FOUND:
+				do_check_stateless_delimiter(args, &reader);
 				state = FETCH_SEND_REQUEST;
 				break;
 			}
 			break;
 		case FETCH_GET_PACK:
+			trace2_region_leave("fetch-pack",
+					    "negotiation_v2",
+					    the_repository);
 			/* Check for shallow-info section */
 			if (process_section_header(&reader, "shallow-info", 1))
 				receive_shallow_info(args, &reader, shallows, si);
@@ -1456,10 +1610,14 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 			if (process_section_header(&reader, "wanted-refs", 1))
 				receive_wanted_refs(&reader, sought, nr_sought);
 
-			/* get the pack */
+			/* get the pack(s) */
+			if (process_section_header(&reader, "packfile-uris", 1))
+				receive_packfile_uris(&reader, &packfile_uris);
 			process_section_header(&reader, "packfile", 0);
-			if (get_pack(args, fd, pack_lockfile))
+			if (get_pack(args, fd, pack_lockfiles,
+				     !packfile_uris.nr, sought, nr_sought))
 				die(_("git fetch-pack: fetch failed."));
+			do_check_stateless_delimiter(args, &reader);
 
 			state = FETCH_DONE;
 			break;
@@ -1468,7 +1626,55 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 		}
 	}
 
-	negotiator.release(&negotiator);
+	for (i = 0; i < packfile_uris.nr; i++) {
+		struct child_process cmd = CHILD_PROCESS_INIT;
+		char packname[GIT_MAX_HEXSZ + 1];
+		const char *uri = packfile_uris.items[i].string +
+			the_hash_algo->hexsz + 1;
+
+		strvec_push(&cmd.args, "http-fetch");
+		strvec_pushf(&cmd.args, "--packfile=%.*s",
+			     (int) the_hash_algo->hexsz,
+			     packfile_uris.items[i].string);
+		strvec_push(&cmd.args, uri);
+		cmd.git_cmd = 1;
+		cmd.no_stdin = 1;
+		cmd.out = -1;
+		if (start_command(&cmd))
+			die("fetch-pack: unable to spawn http-fetch");
+
+		if (read_in_full(cmd.out, packname, 5) < 0 ||
+		    memcmp(packname, "keep\t", 5))
+			die("fetch-pack: expected keep then TAB at start of http-fetch output");
+
+		if (read_in_full(cmd.out, packname,
+				 the_hash_algo->hexsz + 1) < 0 ||
+		    packname[the_hash_algo->hexsz] != '\n')
+			die("fetch-pack: expected hash then LF at end of http-fetch output");
+
+		packname[the_hash_algo->hexsz] = '\0';
+
+		close(cmd.out);
+
+		if (finish_command(&cmd))
+			die("fetch-pack: unable to finish http-fetch");
+
+		if (memcmp(packfile_uris.items[i].string, packname,
+			   the_hash_algo->hexsz))
+			die("fetch-pack: pack downloaded from %s does not match expected hash %.*s",
+			    uri, (int) the_hash_algo->hexsz,
+			    packfile_uris.items[i].string);
+
+		string_list_append_nodup(pack_lockfiles,
+					 xstrfmt("%s/pack/pack-%s.keep",
+						 get_object_directory(),
+						 packname));
+	}
+	string_list_clear(&packfile_uris, 0);
+
+	if (negotiator)
+		negotiator->release(negotiator);
+
 	oidset_clear(&common);
 	return ref;
 }
@@ -1505,8 +1711,14 @@ static void fetch_pack_config(void)
 	git_config_get_bool("repack.usedeltabaseoffset", &prefer_ofs_delta);
 	git_config_get_bool("fetch.fsckobjects", &fetch_fsck_objects);
 	git_config_get_bool("transfer.fsckobjects", &transfer_fsck_objects);
-	git_config_get_string("fetch.negotiationalgorithm",
-			      &negotiation_algorithm);
+	if (!uri_protocols.nr) {
+		char *str;
+
+		if (!git_config_get_string("fetch.uriprotocols", &str) && str) {
+			string_list_split(&uri_protocols, str, ',', -1);
+			free(str);
+		}
+	}
 
 	git_config(fetch_pack_config_cb, NULL);
 }
@@ -1556,9 +1768,9 @@ static void update_shallow(struct fetch_pack_args *args,
 	if (args->deepen && alternate_shallow_file) {
 		if (*alternate_shallow_file == '\0') { /* --unshallow */
 			unlink_or_warn(git_path_shallow(the_repository));
-			rollback_lock_file(&shallow_lock);
+			rollback_shallow_file(the_repository, &shallow_lock);
 		} else
-			commit_lock_file(&shallow_lock);
+			commit_shallow_file(the_repository, &shallow_lock);
 		alternate_shallow_file = NULL;
 		return;
 	}
@@ -1582,7 +1794,7 @@ static void update_shallow(struct fetch_pack_args *args,
 			setup_alternate_shallow(&shallow_lock,
 						&alternate_shallow_file,
 						&extra);
-			commit_lock_file(&shallow_lock);
+			commit_shallow_file(the_repository, &shallow_lock);
 			alternate_shallow_file = NULL;
 		}
 		oid_array_clear(&extra);
@@ -1620,7 +1832,7 @@ static void update_shallow(struct fetch_pack_args *args,
 		setup_alternate_shallow(&shallow_lock,
 					&alternate_shallow_file,
 					&extra);
-		commit_lock_file(&shallow_lock);
+		commit_shallow_file(the_repository, &shallow_lock);
 		oid_array_clear(&extra);
 		oid_array_clear(&ref);
 		alternate_shallow_file = NULL;
@@ -1659,7 +1871,7 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		       const struct ref *ref,
 		       struct ref **sought, int nr_sought,
 		       struct oid_array *shallow,
-		       char **pack_lockfile,
+		       struct string_list *pack_lockfiles,
 		       enum protocol_version version)
 {
 	struct ref *ref_cpy;
@@ -1670,20 +1882,6 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 	if (nr_sought)
 		nr_sought = remove_duplicates_in_refs(sought, nr_sought);
 
-	if (args->no_dependents && !args->filter_options.choice) {
-		/*
-		 * The protocol does not support requesting that only the
-		 * wanted objects be sent, so approximate this by setting a
-		 * "blob:none" filter if no filter is already set. This works
-		 * for all object types: note that wanted blobs will still be
-		 * sent because they are directly specified as a "want".
-		 *
-		 * NEEDSWORK: Add an option in the protocol to request that
-		 * only the wanted objects be sent, and implement it.
-		 */
-		parse_list_objects_filter(&args->filter_options, "blob:none");
-	}
-
 	if (version != protocol_v2 && !ref) {
 		packet_flush(fd[1]);
 		die(_("no matching remote head"));
@@ -1694,11 +1892,11 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		memset(&si, 0, sizeof(si));
 		ref_cpy = do_fetch_pack_v2(args, fd, ref, sought, nr_sought,
 					   &shallows_scratch, &si,
-					   pack_lockfile);
+					   pack_lockfiles);
 	} else {
 		prepare_shallow_info(&si, shallow);
 		ref_cpy = do_fetch_pack(args, fd, ref, sought, nr_sought,
-					&si, pack_lockfile);
+					&si, pack_lockfiles);
 	}
 	reprepare_packed_git(the_repository);
 
@@ -1712,7 +1910,7 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 			error(_("remote did not send all necessary objects"));
 			free_refs(ref_cpy);
 			ref_cpy = NULL;
-			rollback_lock_file(&shallow_lock);
+			rollback_shallow_file(the_repository, &shallow_lock);
 			goto cleanup;
 		}
 		args->connectivity_checked = 1;