Merge branch 'jt/lazy-fetch'

Updates to on-demand fetching code in lazily cloned repositories.

* jt/lazy-fetch:
  fetch: no FETCH_HEAD display if --no-write-fetch-head
  fetch-pack: remove no_dependents code
  promisor-remote: lazy-fetch objects in subprocess
  fetch-pack: do not lazy-fetch during ref iteration
  fetch: only populate existing_refs if needed
  fetch: avoid reading submodule config until needed
  fetch: allow refspecs specified through stdin
  negotiator/noop: add noop fetch negotiator

Documentation/config/fetch.txt

@@ -60,7 +60,10 @@ fetch.negotiationAlgorithm::
 	sent when negotiating the contents of the packfile to be sent by the
 	server. Set to "skipping" to use an algorithm that skips commits in an
 	effort to converge faster, but may result in a larger-than-necessary
-	packfile; The default is "default" which instructs Git to use the default algorithm
+	packfile; or set to "noop" to not send any information at all, which
+	will almost certainly result in a larger-than-necessary packfile, but
+	will skip the negotiation step.
+	The default is "default" which instructs Git to use the default algorithm
 	that never skips commits (unless the server has acknowledged it or one
 	of its descendants). If `feature.experimental` is enabled, then this
 	setting defaults to "skipping".

Documentation/git-fetch.txt

@@ -48,6 +48,10 @@ include::fetch-options.txt[]
 
 include::pull-fetch-param.txt[]
 
+--stdin::
+	Read refspecs, one per line, from stdin in addition to those provided
+	as arguments. The "tag <name>" format is not supported.
+
 include::urls-remotes.txt[]
 
 

Documentation/technical/partial-clone.txt

@@ -171,20 +171,13 @@ additional flag.
 Fetching Missing Objects
 ------------------------
 
-- Fetching of objects is done using the existing transport mechanism using
-  transport_fetch_refs(), setting a new transport option
-  TRANS_OPT_NO_DEPENDENTS to indicate that only the objects themselves are
-  desired, not any object that they refer to.
-+
-Because some transports invoke fetch_pack() in the same process, fetch_pack()
-has been updated to not use any object flags when the corresponding argument
-(no_dependents) is set.
+- Fetching of objects is done by invoking a "git fetch" subprocess.
 
 - The local repository sends a request with the hashes of all requested
-  objects as "want" lines, and does not perform any packfile negotiation.
+  objects, and does not perform any packfile negotiation.
   It then receives a packfile.
 
-- Because we are reusing the existing fetch-pack mechanism, fetching
+- Because we are reusing the existing fetch mechanism, fetching
   currently fetches all objects referred to by the requested objects, even
   though they are not necessary.
 

Makefile

@@ -908,6 +908,7 @@ LIB_OBJS += mergesort.o
 LIB_OBJS += midx.o
 LIB_OBJS += name-hash.o
 LIB_OBJS += negotiator/default.o
+LIB_OBJS += negotiator/noop.o
 LIB_OBJS += negotiator/skipping.o
 LIB_OBJS += notes-cache.o
 LIB_OBJS += notes-merge.o

builtin/fetch-pack.c

@@ -153,10 +153,6 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 			args.from_promisor = 1;
 			continue;
 		}
-		if (!strcmp("--no-dependents", arg)) {
-			args.no_dependents = 1;
-			continue;
-		}
 		if (skip_prefix(arg, ("--" CL_ARG__FILTER "="), &arg)) {
 			parse_list_objects_filter(&args.filter_options, arg);
 			continue;

builtin/fetch.c

@@ -80,6 +80,7 @@ static struct list_objects_filter_options filter_options;
 static struct string_list server_options = STRING_LIST_INIT_DUP;
 static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
 static int fetch_write_commit_graph = -1;
+static int stdin_refspecs = 0;
 
 static int git_fetch_config(const char *k, const char *v, void *cb)
 {
@@ -205,6 +206,8 @@ static struct option builtin_fetch_options[] = {
 		 N_("check for forced-updates on all updated branches")),
 	OPT_BOOL(0, "write-commit-graph", &fetch_write_commit_graph,
 		 N_("write the commit-graph after fetching")),
+	OPT_BOOL(0, "stdin", &stdin_refspecs,
+		 N_("accept refspecs from stdin")),
 	OPT_END()
 };
 
@@ -442,6 +445,7 @@ static struct ref *get_ref_map(struct remote *remote,
 	struct ref *orefs = NULL, **oref_tail = &orefs;
 
 	struct hashmap existing_refs;
+	int existing_refs_populated = 0;
 
 	if (rs->nr) {
 		struct refspec *fetch_refspec;
@@ -535,15 +539,18 @@ static struct ref *get_ref_map(struct remote *remote,
 
 	ref_map = ref_remove_duplicates(ref_map);
 
-	refname_hash_init(&existing_refs);
-	for_each_ref(add_one_refname, &existing_refs);
-
 	for (rm = ref_map; rm; rm = rm->next) {
 		if (rm->peer_ref) {
 			const char *refname = rm->peer_ref->name;
 			struct refname_hash_entry *peer_item;
 			unsigned int hash = strhash(refname);
 
+			if (!existing_refs_populated) {
+				refname_hash_init(&existing_refs);
+				for_each_ref(add_one_refname, &existing_refs);
+				existing_refs_populated = 1;
+			}
+
 			peer_item = hashmap_get_entry_from_hash(&existing_refs,
 						hash, refname,
 						struct refname_hash_entry, ent);
@@ -553,7 +560,8 @@ static struct ref *get_ref_map(struct remote *remote,
 			}
 		}
 	}
-	hashmap_free_entries(&existing_refs, struct refname_hash_entry, ent);
+	if (existing_refs_populated)
+		hashmap_free_entries(&existing_refs, struct refname_hash_entry, ent);
 
 	return ref_map;
 }
@@ -1015,11 +1023,17 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 				rc |= update_local_ref(ref, what, rm, &note,
 						       summary_width);
 				free(ref);
-			} else
+			} else if (write_fetch_head || dry_run) {
+				/*
+				 * Display fetches written to FETCH_HEAD (or
+				 * would be written to FETCH_HEAD, if --dry-run
+				 * is set).
+				 */
 				format_display(&note, '*',
 					       *kind ? kind : "branch", NULL,
 					       *what ? what : "HEAD",
 					       "FETCH_HEAD", summary_width);
+			}
 			if (note.len) {
 				if (verbosity >= 0 && !shown_url) {
 					fprintf(stderr, _("From %.*s\n"),
@@ -1680,7 +1694,8 @@ static inline void fetch_one_setup_partial(struct remote *remote)
 	return;
 }
 
-static int fetch_one(struct remote *remote, int argc, const char **argv, int prune_tags_ok)
+static int fetch_one(struct remote *remote, int argc, const char **argv,
+		     int prune_tags_ok, int use_stdin_refspecs)
 {
 	struct refspec rs = REFSPEC_INIT_FETCH;
 	int i;
@@ -1737,6 +1752,13 @@ static int fetch_one(struct remote *remote, int argc, const char **argv, int pru
 		}
 	}
 
+	if (use_stdin_refspecs) {
+		struct strbuf line = STRBUF_INIT;
+		while (strbuf_getline_lf(&line, stdin) != EOF)
+			refspec_append(&rs, line.buf);
+		strbuf_release(&line);
+	}
+
 	if (server_options.nr)
 		gtransport->server_options = &server_options;
 
@@ -1771,12 +1793,18 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 		free(anon);
 	}
 
-	fetch_config_from_gitmodules(&submodule_fetch_jobs_config,
-				     &recurse_submodules);
 	git_config(git_fetch_config, NULL);
 
 	argc = parse_options(argc, argv, prefix,
 			     builtin_fetch_options, builtin_fetch_usage, 0);
+	if (recurse_submodules != RECURSE_SUBMODULES_OFF) {
+		int *sfjc = submodule_fetch_jobs_config == -1
+			    ? &submodule_fetch_jobs_config : NULL;
+		int *rs = recurse_submodules == RECURSE_SUBMODULES_DEFAULT
+			  ? &recurse_submodules : NULL;
+
+		fetch_config_from_gitmodules(sfjc, rs);
+	}
 
 	if (deepen_relative) {
 		if (deepen_relative < 0)
@@ -1837,7 +1865,7 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 	if (remote) {
 		if (filter_options.choice || has_promisor_remote())
 			fetch_one_setup_partial(remote);
-		result = fetch_one(remote, argc, argv, prune_tags_ok);
+		result = fetch_one(remote, argc, argv, prune_tags_ok, stdin_refspecs);
 	} else {
 		int max_children = max_jobs;
 
@@ -1845,6 +1873,10 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)
 			die(_("--filter can only be used with the remote "
 			      "configured in extensions.partialclone"));
 
+		if (stdin_refspecs)
+			die(_("--stdin can only be used when fetching "
+			      "from one remote"));
+
 		if (max_children < 0)
 			max_children = fetch_parallel_config;
 

fetch-negotiator.c

@@ -2,6 +2,7 @@
 #include "fetch-negotiator.h"
 #include "negotiator/default.h"
 #include "negotiator/skipping.h"
+#include "negotiator/noop.h"
 #include "repository.h"
 
 void fetch_negotiator_init(struct repository *r,
@@ -13,6 +14,10 @@ void fetch_negotiator_init(struct repository *r,
 		skipping_negotiator_init(negotiator);
 		return;
 
+	case FETCH_NEGOTIATION_NOOP:
+		noop_negotiator_init(negotiator);
+		return;
+
 	case FETCH_NEGOTIATION_DEFAULT:
 	default:
 		default_negotiator_init(negotiator);

fetch-pack.c

@@ -108,24 +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 {
@@ -201,7 +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
@@ -230,13 +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;
 }
 
@@ -262,10 +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) {
@@ -282,12 +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;
 		}
@@ -387,8 +404,6 @@ static int find_common(struct fetch_negotiator *negotiator,
 	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));
@@ -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
@@ -702,7 +705,7 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 	 */
 	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)
@@ -716,16 +719,12 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator,
 	 */
 	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);
 
@@ -967,12 +966,8 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	struct fetch_negotiator negotiator_alloc;
 	struct fetch_negotiator *negotiator;
 
-	if (args->no_dependents) {
-		negotiator = NULL;
-	} else {
-		negotiator = &negotiator_alloc;
-		fetch_negotiator_init(r, negotiator);
-	}
+	negotiator = &negotiator_alloc;
+	fetch_negotiator_init(r, negotiator);
 
 	sort_ref_list(&ref, ref_compare_name);
 	QSORT(sought, nr_sought, cmp_ref_by_name);
@@ -1060,15 +1055,11 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
 	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 (!args->keep_pack)
@@ -1117,7 +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);
 
@@ -1134,12 +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;
 		}
@@ -1273,19 +1260,14 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	}
 
 	/* add wants */
-	add_wants(args->no_dependents, wants, &req_buf);
+	add_wants(wants, &req_buf);
 
-	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);
+	/* 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);
-	}
+	/* Add initial haves */
+	ret = add_haves(negotiator, seen_ack, &req_buf,
+			haves_to_send, in_vain);
 
 	/* Send request */
 	packet_buf_flush(&req_buf);
@@ -1545,12 +1527,8 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	struct string_list packfile_uris = STRING_LIST_INIT_DUP;
 	int i;
 
-	if (args->no_dependents) {
-		negotiator = NULL;
-	} else {
-		negotiator = &negotiator_alloc;
-		fetch_negotiator_init(r, negotiator);
-	}
+	negotiator = &negotiator_alloc;
+	fetch_negotiator_init(r, negotiator);
 
 	packet_reader_init(&reader, fd[0], NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
@@ -1574,21 +1552,16 @@ 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 (!negotiation_started) {
@@ -1909,20 +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"));

fetch-pack.h

@@ -50,20 +50,6 @@ struct fetch_pack_args {
 	 */
 	unsigned from_promisor:1;
 
-	/*
-	 * Attempt to fetch only the wanted objects, and not any objects
-	 * referred to by them. Due to protocol limitations, extraneous
-	 * objects may still be included. (When fetching non-blob
-	 * objects, only blobs are excluded; when fetching a blob, the
-	 * blob itself will still be sent. The client does not need to
-	 * know whether a wanted object is a blob or not.)
-	 *
-	 * If 1, fetch_pack() will also not modify any object flags.
-	 * This allows fetch_pack() to safely be called by any function,
-	 * 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

negotiator/noop.c

@@ -0,0 +1,44 @@
+#include "cache.h"
+#include "noop.h"
+#include "../commit.h"
+#include "../fetch-negotiator.h"
+
+static void known_common(struct fetch_negotiator *n, struct commit *c)
+{
+	/* do nothing */
+}
+
+static void add_tip(struct fetch_negotiator *n, struct commit *c)
+{
+	/* do nothing */
+}
+
+static const struct object_id *next(struct fetch_negotiator *n)
+{
+	return NULL;
+}
+
+static int ack(struct fetch_negotiator *n, struct commit *c)
+{
+	/*
+	 * This negotiator does not emit any commits, so there is no commit to
+	 * be acknowledged. If there is any ack, there is a bug.
+	 */
+	BUG("ack with noop negotiator, which does not emit any commits");
+	return 0;
+}
+
+static void release(struct fetch_negotiator *n)
+{
+	/* nothing to release */
+}
+
+void noop_negotiator_init(struct fetch_negotiator *negotiator)
+{
+	negotiator->known_common = known_common;
+	negotiator->add_tip = add_tip;
+	negotiator->next = next;
+	negotiator->ack = ack;
+	negotiator->release = release;
+	negotiator->data = NULL;
+}

negotiator/noop.h

@@ -0,0 +1,8 @@
+#ifndef NEGOTIATOR_NOOP_H
+#define NEGOTIATOR_NOOP_H
+
+struct fetch_negotiator;
+
+void noop_negotiator_init(struct fetch_negotiator *negotiator);
+
+#endif

promisor-remote.c

@@ -3,6 +3,7 @@
 #include "promisor-remote.h"
 #include "config.h"
 #include "transport.h"
+#include "strvec.h"
 
 static char *repository_format_partial_clone;
 static const char *core_partial_clone_filter_default;
@@ -12,39 +13,34 @@ void set_repository_format_partial_clone(char *partial_clone)
 	repository_format_partial_clone = xstrdup_or_null(partial_clone);
 }
 
-static int fetch_refs(const char *remote_name, struct ref *ref)
-{
-	struct remote *remote;
-	struct transport *transport;
-	int res;
-
-	remote = remote_get(remote_name);
-	if (!remote->url[0])
-		die(_("Remote with no URL"));
-	transport = transport_get(remote, remote->url[0]);
-
-	transport_set_option(transport, TRANS_OPT_FROM_PROMISOR, "1");
-	transport_set_option(transport, TRANS_OPT_NO_DEPENDENTS, "1");
-	res = transport_fetch_refs(transport, ref);
-
-	return res;
-}
-
 static int fetch_objects(const char *remote_name,
 			 const struct object_id *oids,
 			 int oid_nr)
 {
-	struct ref *ref = NULL;
+	struct child_process child = CHILD_PROCESS_INIT;
 	int i;
+	FILE *child_in;
+
+	child.git_cmd = 1;
+	child.in = -1;
+	strvec_pushl(&child.args, "-c", "fetch.negotiationAlgorithm=noop",
+		     "fetch", remote_name, "--no-tags",
+		     "--no-write-fetch-head", "--recurse-submodules=no",
+		     "--filter=blob:none", "--stdin", NULL);
+	if (start_command(&child))
+		die(_("promisor-remote: unable to fork off fetch subprocess"));
+	child_in = xfdopen(child.in, "w");
 
 	for (i = 0; i < oid_nr; i++) {
-		struct ref *new_ref = alloc_ref(oid_to_hex(&oids[i]));
-		oidcpy(&new_ref->old_oid, &oids[i]);
-		new_ref->exact_oid = 1;
-		new_ref->next = ref;
-		ref = new_ref;
+		if (fputs(oid_to_hex(&oids[i]), child_in) < 0)
+			die_errno(_("promisor-remote: could not write to fetch subprocess"));
+		if (fputc('\n', child_in) < 0)
+			die_errno(_("promisor-remote: could not write to fetch subprocess"));
 	}
-	return fetch_refs(remote_name, ref);
+
+	if (fclose(child_in) < 0)
+		die_errno(_("promisor-remote: could not close stdin to fetch subprocess"));
+	return finish_command(&child) ? -1 : 0;
 }
 
 static struct promisor_remote *promisors;

remote-curl.c

@@ -43,7 +43,6 @@ struct options {
 		/* see documentation of corresponding flag in fetch-pack.h */
 		from_promisor : 1,
 
-		no_dependents : 1,
 		atomic : 1,
 		object_format : 1;
 	const struct git_hash_algo *hash_algo;
@@ -193,9 +192,6 @@ static int set_option(const char *name, const char *value)
 	} else if (!strcmp(name, "from-promisor")) {
 		options.from_promisor = 1;
 		return 0;
-	} else if (!strcmp(name, "no-dependents")) {
-		options.no_dependents = 1;
-		return 0;
 	} else if (!strcmp(name, "filter")) {
 		options.filter = xstrdup(value);
 		return 0;
@@ -1178,8 +1174,6 @@ static int fetch_git(struct discovery *heads,
 		strvec_push(&args, "--deepen-relative");
 	if (options.from_promisor)
 		strvec_push(&args, "--from-promisor");
-	if (options.no_dependents)
-		strvec_push(&args, "--no-dependents");
 	if (options.filter)
 		strvec_pushf(&args, "--filter=%s", options.filter);
 	strvec_push(&args, url.buf);

repo-settings.c

@@ -39,6 +39,8 @@ void prepare_repo_settings(struct repository *r)
 	if (!repo_config_get_string(r, "fetch.negotiationalgorithm", &strval)) {
 		if (!strcasecmp(strval, "skipping"))
 			r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_SKIPPING;
+		else if (!strcasecmp(strval, "noop"))
+			r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_NOOP;
 		else
 			r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_DEFAULT;
 	}

repository.h

@@ -23,6 +23,7 @@ enum fetch_negotiation_setting {
 	FETCH_NEGOTIATION_NONE = 0,
 	FETCH_NEGOTIATION_DEFAULT = 1,
 	FETCH_NEGOTIATION_SKIPPING = 2,
+	FETCH_NEGOTIATION_NOOP = 3,
 };
 
 struct repo_settings {

submodule-config.c

@@ -777,10 +777,14 @@ static int gitmodules_fetch_config(const char *var, const char *value, void *cb)
 {
 	struct fetch_config *config = cb;
 	if (!strcmp(var, "submodule.fetchjobs")) {
-		*(config->max_children) = parse_submodule_fetchjobs(var, value);
+		if (config->max_children)
+			*(config->max_children) =
+				parse_submodule_fetchjobs(var, value);
 		return 0;
 	} else if (!strcmp(var, "fetch.recursesubmodules")) {
-		*(config->recurse_submodules) = parse_fetch_recurse_submodules_arg(var, value);
+		if (config->recurse_submodules)
+			*(config->recurse_submodules) =
+				parse_fetch_recurse_submodules_arg(var, value);
 		return 0;
 	}
 

t/t0410-partial-clone.sh

@@ -183,7 +183,7 @@ test_expect_success 'missing CLI object, but promised, passes fsck' '
 '
 
 test_expect_success 'fetching of missing objects' '
-	rm -rf repo &&
+	rm -rf repo err &&
 	test_create_repo server &&
 	test_commit -C server foo &&
 	git -C server repack -a -d --write-bitmap-index &&
@@ -194,7 +194,10 @@ test_expect_success 'fetching of missing objects' '
 
 	git -C repo config core.repositoryformatversion 1 &&
 	git -C repo config extensions.partialclone "origin" &&
-	git -C repo cat-file -p "$HASH" &&
+	git -C repo cat-file -p "$HASH" 2>err &&
+
+	# Ensure that no spurious FETCH_HEAD messages are written
+	! grep FETCH_HEAD err &&
 
 	# Ensure that the .promisor file is written, and check that its
 	# associated packfile contains the object
@@ -214,7 +217,7 @@ test_expect_success 'fetching of missing objects works with ref-in-want enabled'
 	rm -rf repo/.git/objects/* &&
 	rm -f trace &&
 	GIT_TRACE_PACKET="$(pwd)/trace" git -C repo cat-file -p "$HASH" &&
-	grep "git< fetch=.*ref-in-want" trace
+	grep "fetch< fetch=.*ref-in-want" trace
 '
 
 test_expect_success 'fetching of missing objects from another promisor remote' '

t/t4067-diff-partial-clone.sh

@@ -20,7 +20,7 @@ test_expect_success 'git show batches blobs' '
 	# Ensure that there is exactly 1 negotiation by checking that there is
 	# only 1 "done" line sent. ("done" marks the end of negotiation.)
 	GIT_TRACE_PACKET="$(pwd)/trace" git -C client show HEAD &&
-	grep "git> done" trace >done_lines &&
+	grep "fetch> done" trace >done_lines &&
 	test_line_count = 1 done_lines
 '
 
@@ -44,7 +44,7 @@ test_expect_success 'diff batches blobs' '
 	# Ensure that there is exactly 1 negotiation by checking that there is
 	# only 1 "done" line sent. ("done" marks the end of negotiation.)
 	GIT_TRACE_PACKET="$(pwd)/trace" git -C client diff HEAD^ HEAD &&
-	grep "git> done" trace >done_lines &&
+	grep "fetch> done" trace >done_lines &&
 	test_line_count = 1 done_lines
 '
 
@@ -127,7 +127,7 @@ test_expect_success 'diff with rename detection batches blobs' '
 	# only 1 "done" line sent. ("done" marks the end of negotiation.)
 	GIT_TRACE_PACKET="$(pwd)/trace" git -C client diff --raw -M HEAD^ HEAD >out &&
 	grep ":100644 100644.*R[0-9][0-9][0-9].*b.*c" out &&
-	grep "git> done" trace >done_lines &&
+	grep "fetch> done" trace >done_lines &&
 	test_line_count = 1 done_lines
 '
 
@@ -175,7 +175,7 @@ test_expect_success 'diff --break-rewrites fetches only if necessary, and batche
 	# by checking that there is only 1 "done" line sent. ("done" marks the
 	# end of negotiation.)
 	GIT_TRACE_PACKET="$(pwd)/trace" git -C client diff --break-rewrites --raw -M HEAD^ HEAD &&
-	grep "git> done" trace >done_lines &&
+	grep "fetch> done" trace >done_lines &&
 	test_line_count = 1 done_lines
 '
 

t/t5300-pack-object.sh

@@ -528,7 +528,7 @@ test_expect_success 'prefetch objects' '
 	TWO=$(git -C server rev-parse three_branch^) &&
 	git -C client fetch --filter=blob:none origin "$TWO" &&
 	GIT_TRACE_PACKET=$(pwd)/trace git -C client push origin "$TWO":refs/heads/two_branch &&
-	grep "git> done" trace >donelines &&
+	grep "fetch> done" trace >donelines &&
 	test_line_count = 1 donelines
 '
 

t/t5510-fetch.sh

@@ -543,16 +543,18 @@ test_expect_success 'fetch into the current branch with --update-head-ok' '
 
 '
 
-test_expect_success 'fetch --dry-run does not touch FETCH_HEAD' '
-	rm -f .git/FETCH_HEAD &&
-	git fetch --dry-run . &&
-	! test -f .git/FETCH_HEAD
+test_expect_success 'fetch --dry-run does not touch FETCH_HEAD, but still prints what would be written' '
+	rm -f .git/FETCH_HEAD err &&
+	git fetch --dry-run . 2>err &&
+	! test -f .git/FETCH_HEAD &&
+	grep FETCH_HEAD err
 '
 
-test_expect_success '--no-write-fetch-head does not touch FETCH_HEAD' '
-	rm -f .git/FETCH_HEAD &&
-	git fetch --no-write-fetch-head . &&
-	! test -f .git/FETCH_HEAD
+test_expect_success '--no-write-fetch-head does not touch FETCH_HEAD, and does not print what would be written' '
+	rm -f .git/FETCH_HEAD err &&
+	git fetch --no-write-fetch-head . 2>err &&
+	! test -f .git/FETCH_HEAD &&
+	! grep FETCH_HEAD err
 '
 
 test_expect_success '--write-fetch-head gets defeated by --dry-run' '

t/t5554-noop-fetch-negotiator.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+test_description='test noop fetch negotiator'
+. ./test-lib.sh
+
+test_expect_success 'noop negotiator does not emit any "have"' '
+	rm -f trace &&
+
+	test_create_repo server &&
+	test_commit -C server to_fetch &&
+
+	test_create_repo client &&
+	test_commit -C client we_have &&
+
+	test_config -C client fetch.negotiationalgorithm noop &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch "$(pwd)/server" &&
+
+	! grep "fetch> have" trace &&
+	grep "fetch> done" trace
+'
+
+test_done

t/t5601-clone.sh

@@ -704,7 +704,7 @@ test_expect_success 'batch missing blob request during checkout' '
 	# Ensure that there is only one negotiation by checking that there is
 	# only "done" line sent. ("done" marks the end of negotiation.)
 	GIT_TRACE_PACKET="$(pwd)/trace" git -C client checkout HEAD^ &&
-	grep "git> done" trace >done_lines &&
+	grep "fetch> done" trace >done_lines &&
 	test_line_count = 1 done_lines
 '
 

t/t5616-partial-clone.sh

@@ -433,6 +433,26 @@ test_expect_success 'fetch lazy-fetches only to resolve deltas, protocol v2' '
 	grep "want $(cat hash)" trace
 '
 
+test_expect_success 'fetch does not lazy-fetch missing targets of its refs' '
+	rm -rf server client trace &&
+
+	test_create_repo server &&
+	test_config -C server uploadpack.allowfilter 1 &&
+	test_config -C server uploadpack.allowanysha1inwant 1 &&
+	test_commit -C server foo &&
+
+	git clone --filter=blob:none "file://$(pwd)/server" client &&
+	# Make all refs point to nothing by deleting all objects.
+	rm client/.git/objects/pack/* &&
+
+	test_commit -C server bar &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		--no-tags --recurse-submodules=no \
+		origin refs/tags/bar &&
+	FOO_HASH=$(git -C server rev-parse foo) &&
+	! grep "want $FOO_HASH" trace
+'
+
 # The following two tests must be in this order. It is important that
 # the srv.bare repository did not have tags during clone, but has tags
 # in the fetch.

transport.c

@@ -232,9 +232,6 @@ static int set_git_option(struct git_transport_options *opts,
 	} else if (!strcmp(name, TRANS_OPT_FROM_PROMISOR)) {
 		opts->from_promisor = !!value;
 		return 0;
-	} else if (!strcmp(name, TRANS_OPT_NO_DEPENDENTS)) {
-		opts->no_dependents = !!value;
-		return 0;
 	} else if (!strcmp(name, TRANS_OPT_LIST_OBJECTS_FILTER)) {
 		list_objects_filter_die_if_populated(&opts->filter_options);
 		parse_list_objects_filter(&opts->filter_options, value);
@@ -359,7 +356,6 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.cloning = transport->cloning;
 	args.update_shallow = data->options.update_shallow;
 	args.from_promisor = data->options.from_promisor;
-	args.no_dependents = data->options.no_dependents;
 	args.filter_options = data->options.filter_options;
 	args.stateless_rpc = transport->stateless_rpc;
 	args.server_options = transport->server_options;

transport.h

@@ -19,8 +19,6 @@ struct git_transport_options {
 	/* see documentation of corresponding flag in fetch-pack.h */
 	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
@@ -204,12 +202,6 @@ void transport_check_allowed(const char *type);
 /* Indicate that these objects are being fetched by a promisor */
 #define TRANS_OPT_FROM_PROMISOR "from-promisor"
 
-/*
- * Indicate that only the objects wanted need to be fetched, not their
- * dependents
- */
-#define TRANS_OPT_NO_DEPENDENTS "no-dependents"
-
 /* Filter objects for partial clone and fetch */
 #define TRANS_OPT_LIST_OBJECTS_FILTER "filter"