Merge branch 'tb/midx-avoid-cruft-packs' into jch

"pack-objects" has been taught to avoid pointing into objects in
cruft packs from midx.

Ready?

* tb/midx-avoid-cruft-packs:
  repack: exclude cruft pack(s) from the MIDX where possible
  pack-objects: introduce '--stdin-packs=follow'
  pack-objects: swap 'show_{object,commit}_pack_hint'
  pack-objects: fix typo in 'show_object_pack_hint()'
  pack-objects: perform name-hash traversal for unpacked objects
  pack-objects: declare 'rev_info' for '--stdin-packs' earlier
  pack-objects: factor out handling '--stdin-packs'
  pack-objects: limit scope in 'add_object_entry_from_pack()'
  pack-objects: use standard option incompatibility functions

Author: gitster

Documentation/config/repack.adoc

@@ -39,3 +39,10 @@ repack.cruftThreads::
 	a cruft pack and the respective parameters are not given over
 	the command line. See similarly named `pack.*` configuration
 	variables for defaults and meaning.
+
+repack.midxMustContainCruft::
+	When set to true, linkgit:git-repack[1] will unconditionally include
+	cruft pack(s), if any, in the multi-pack index when invoked with
+	`--write-midx`. When false, cruft packs are only included in the MIDX
+	when necessary (e.g., because they might be required to form a
+	reachability closure with MIDX bitmaps). Defaults to true.

Documentation/git-pack-objects.adoc

@@ -87,13 +87,21 @@ base-name::
 	reference was included in the resulting packfile.  This
 	can be useful to send new tags to native Git clients.
 
---stdin-packs::
+--stdin-packs[=<mode>]::
 	Read the basenames of packfiles (e.g., `pack-1234abcd.pack`)
 	from the standard input, instead of object names or revision
 	arguments. The resulting pack contains all objects listed in the
 	included packs (those not beginning with `^`), excluding any
 	objects listed in the excluded packs (beginning with `^`).
 +
+When `mode` is "follow", objects from packs not listed on stdin receive
+special treatment. Objects within unlisted packs will be included if
+those objects are (1) reachable from the included packs, and (2) not
+found in any excluded packs. This mode is useful, for example, to
+resurrect once-unreachable objects found in cruft packs to generate
+packs which are closed under reachability up to the boundary set by the
+excluded packs.
++
 Incompatible with `--revs`, or options that imply `--revs` (such as
 `--all`), with the exception of `--unpacked`, which is compatible.
 

builtin/pack-objects.c

@@ -284,6 +284,12 @@ static struct oidmap configured_exclusions;
 static struct oidset excluded_by_config;
 static int name_hash_version = -1;
 
+enum stdin_packs_mode {
+	STDIN_PACKS_MODE_NONE,
+	STDIN_PACKS_MODE_STANDARD,
+	STDIN_PACKS_MODE_FOLLOW,
+};
+
 /**
  * Check whether the name_hash_version chosen by user input is appropriate,
  * and also validate whether it is compatible with other features.
@@ -3725,14 +3731,14 @@ static int add_object_entry_from_pack(const struct object_id *oid,
 		return 0;
 
 	if (p) {
-		struct rev_info *revs = _data;
 		struct object_info oi = OBJECT_INFO_INIT;
 
 		oi.typep = &type;
 		if (packed_object_info(the_repository, p, ofs, &oi) < 0) {
 			die(_("could not get type of object %s in pack %s"),
 			    oid_to_hex(oid), p->pack_name);
 		} else if (type == OBJ_COMMIT) {
+			struct rev_info *revs = _data;
 			/*
 			 * commits in included packs are used as starting points for the
 			 * subsequent revision walk
@@ -3748,32 +3754,45 @@ static int add_object_entry_from_pack(const struct object_id *oid,
 	return 0;
 }
 
-static void show_commit_pack_hint(struct commit *commit UNUSED,
-				  void *data UNUSED)
+static void show_object_pack_hint(struct object *object, const char *name,
+				  void *data)
 {
-	/* nothing to do; commits don't have a namehash */
+	enum stdin_packs_mode mode = *(enum stdin_packs_mode *)data;
+	if (mode == STDIN_PACKS_MODE_FOLLOW) {
+		add_object_entry(&object->oid, object->type, name, 0);
+	} else {
+		struct object_entry *oe = packlist_find(&to_pack, &object->oid);
+		if (!oe)
+			return;
+
+		/*
+		 * Our 'to_pack' list was constructed by iterating all
+		 * objects packed in included packs, and so doesn't have
+		 * a non-zero hash field that you would typically pick
+		 * up during a reachability traversal.
+		 *
+		 * Make a best-effort attempt to fill in the ->hash and
+		 * ->no_try_delta fields here in order to perhaps
+		 * improve the delta selection process.
+		 */
+		oe->hash = pack_name_hash_fn(name);
+		oe->no_try_delta = name && no_try_delta(name);
+
+		stdin_packs_hints_nr++;
+	}
 }
 
-static void show_object_pack_hint(struct object *object, const char *name,
-				  void *data UNUSED)
+static void show_commit_pack_hint(struct commit *commit, void *data)
 {
-	struct object_entry *oe = packlist_find(&to_pack, &object->oid);
-	if (!oe)
+	enum stdin_packs_mode mode = *(enum stdin_packs_mode *)data;
+
+	if (mode == STDIN_PACKS_MODE_FOLLOW) {
+		show_object_pack_hint((struct object *)commit, "", data);
 		return;
+	}
 
-	/*
-	 * Our 'to_pack' list was constructed by iterating all objects packed in
-	 * included packs, and so doesn't have a non-zero hash field that you
-	 * would typically pick up during a reachability traversal.
-	 *
-	 * Make a best-effort attempt to fill in the ->hash and ->no_try_delta
-	 * here using a now in order to perhaps improve the delta selection
-	 * process.
-	 */
-	oe->hash = pack_name_hash_fn(name);
-	oe->no_try_delta = name && no_try_delta(name);
+	/* nothing to do; commits don't have a namehash */
 
-	stdin_packs_hints_nr++;
 }
 
 static int pack_mtime_cmp(const void *_a, const void *_b)
@@ -3793,32 +3812,14 @@ static int pack_mtime_cmp(const void *_a, const void *_b)
 		return 0;
 }
 
-static void read_packs_list_from_stdin(void)
+static void read_packs_list_from_stdin(struct rev_info *revs)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct string_list include_packs = STRING_LIST_INIT_DUP;
 	struct string_list exclude_packs = STRING_LIST_INIT_DUP;
 	struct string_list_item *item = NULL;
 
 	struct packed_git *p;
-	struct rev_info revs;
-
-	repo_init_revisions(the_repository, &revs, NULL);
-	/*
-	 * Use a revision walk to fill in the namehash of objects in the include
-	 * packs. To save time, we'll avoid traversing through objects that are
-	 * in excluded packs.
-	 *
-	 * That may cause us to avoid populating all of the namehash fields of
-	 * all included objects, but our goal is best-effort, since this is only
-	 * an optimization during delta selection.
-	 */
-	revs.no_kept_objects = 1;
-	revs.keep_pack_cache_flags |= IN_CORE_KEEP_PACKS;
-	revs.blob_objects = 1;
-	revs.tree_objects = 1;
-	revs.tag_objects = 1;
-	revs.ignore_missing_links = 1;
 
 	while (strbuf_getline(&buf, stdin) != EOF) {
 		if (!buf.len)
@@ -3888,25 +3889,55 @@ static void read_packs_list_from_stdin(void)
 		struct packed_git *p = item->util;
 		for_each_object_in_pack(p,
 					add_object_entry_from_pack,
-					&revs,
+					revs,
 					FOR_EACH_OBJECT_PACK_ORDER);
 	}
 
+	strbuf_release(&buf);
+	string_list_clear(&include_packs, 0);
+	string_list_clear(&exclude_packs, 0);
+}
+
+static void add_unreachable_loose_objects(struct rev_info *revs);
+
+static void read_stdin_packs(enum stdin_packs_mode mode, int rev_list_unpacked)
+{
+	struct rev_info revs;
+
+	repo_init_revisions(the_repository, &revs, NULL);
+	/*
+	 * Use a revision walk to fill in the namehash of objects in the include
+	 * packs. To save time, we'll avoid traversing through objects that are
+	 * in excluded packs.
+	 *
+	 * That may cause us to avoid populating all of the namehash fields of
+	 * all included objects, but our goal is best-effort, since this is only
+	 * an optimization during delta selection.
+	 */
+	revs.no_kept_objects = 1;
+	revs.keep_pack_cache_flags |= IN_CORE_KEEP_PACKS;
+	revs.blob_objects = 1;
+	revs.tree_objects = 1;
+	revs.tag_objects = 1;
+	revs.ignore_missing_links = 1;
+
+	/* avoids adding objects in excluded packs */
+	ignore_packed_keep_in_core = 1;
+	read_packs_list_from_stdin(&revs);
+	if (rev_list_unpacked)
+		add_unreachable_loose_objects(&revs);
+
 	if (prepare_revision_walk(&revs))
 		die(_("revision walk setup failed"));
 	traverse_commit_list(&revs,
 			     show_commit_pack_hint,
 			     show_object_pack_hint,
-			     NULL);
+			     &mode);
 
 	trace2_data_intmax("pack-objects", the_repository, "stdin_packs_found",
 			   stdin_packs_found_nr);
 	trace2_data_intmax("pack-objects", the_repository, "stdin_packs_hints",
 			   stdin_packs_hints_nr);
-
-	strbuf_release(&buf);
-	string_list_clear(&include_packs, 0);
-	string_list_clear(&exclude_packs, 0);
 }
 
 static void add_cruft_object_entry(const struct object_id *oid, enum object_type type,
@@ -4004,7 +4035,6 @@ static void mark_pack_kept_in_core(struct string_list *packs, unsigned keep)
 	}
 }
 
-static void add_unreachable_loose_objects(void);
 static void add_objects_in_unpacked_packs(void);
 
 static void enumerate_cruft_objects(void)
@@ -4014,7 +4044,7 @@ static void enumerate_cruft_objects(void)
 						_("Enumerating cruft objects"), 0);
 
 	add_objects_in_unpacked_packs();
-	add_unreachable_loose_objects();
+	add_unreachable_loose_objects(NULL);
 
 	stop_progress(&progress_state);
 }
@@ -4292,8 +4322,9 @@ static void add_objects_in_unpacked_packs(void)
 }
 
 static int add_loose_object(const struct object_id *oid, const char *path,
-			    void *data UNUSED)
+			    void *data)
 {
+	struct rev_info *revs = data;
 	enum object_type type = oid_object_info(the_repository, oid, NULL);
 
 	if (type < 0) {
@@ -4314,6 +4345,10 @@ static int add_loose_object(const struct object_id *oid, const char *path,
 	} else {
 		add_object_entry(oid, type, "", 0);
 	}
+
+	if (revs && type == OBJ_COMMIT)
+		add_pending_oid(revs, NULL, oid, 0);
+
 	return 0;
 }
 
@@ -4322,11 +4357,10 @@ static int add_loose_object(const struct object_id *oid, const char *path,
  * add_object_entry will weed out duplicates, so we just add every
  * loose object we find.
  */
-static void add_unreachable_loose_objects(void)
+static void add_unreachable_loose_objects(struct rev_info *revs)
 {
 	for_each_loose_file_in_objdir(repo_get_object_directory(the_repository),
-				      add_loose_object,
-				      NULL, NULL, NULL);
+				      add_loose_object, NULL, NULL, revs);
 }
 
 static int has_sha1_pack_kept_or_nonlocal(const struct object_id *oid)
@@ -4673,7 +4707,7 @@ static void get_object_list(struct rev_info *revs, int ac, const char **av)
 	if (keep_unreachable)
 		add_objects_in_unpacked_packs();
 	if (pack_loose_unreachable)
-		add_unreachable_loose_objects();
+		add_unreachable_loose_objects(NULL);
 	if (unpack_unreachable)
 		loosen_unused_packed_objects();
 
@@ -4780,6 +4814,23 @@ static int is_not_in_promisor_pack(struct commit *commit, void *data) {
 	return is_not_in_promisor_pack_obj((struct object *) commit, data);
 }
 
+static int parse_stdin_packs_mode(const struct option *opt, const char *arg,
+				  int unset)
+{
+	enum stdin_packs_mode *mode = opt->value;
+
+	if (unset)
+		*mode = STDIN_PACKS_MODE_NONE;
+	else if (!arg || !*arg)
+		*mode = STDIN_PACKS_MODE_STANDARD;
+	else if (!strcmp(arg, "follow"))
+		*mode = STDIN_PACKS_MODE_FOLLOW;
+	else
+		die(_("invalid value for '%s': '%s'"), opt->long_name, arg);
+
+	return 0;
+}
+
 int cmd_pack_objects(int argc,
 		     const char **argv,
 		     const char *prefix,
@@ -4790,7 +4841,7 @@ int cmd_pack_objects(int argc,
 	struct strvec rp = STRVEC_INIT;
 	int rev_list_unpacked = 0, rev_list_all = 0, rev_list_reflog = 0;
 	int rev_list_index = 0;
-	int stdin_packs = 0;
+	enum stdin_packs_mode stdin_packs = STDIN_PACKS_MODE_NONE;
 	struct string_list keep_pack_list = STRING_LIST_INIT_NODUP;
 	struct list_objects_filter_options filter_options =
 		LIST_OBJECTS_FILTER_INIT;
@@ -4845,6 +4896,9 @@ int cmd_pack_objects(int argc,
 		OPT_SET_INT_F(0, "indexed-objects", &rev_list_index,
 			      N_("include objects referred to by the index"),
 			      1, PARSE_OPT_NONEG),
+		OPT_CALLBACK_F(0, "stdin-packs", &stdin_packs, N_("mode"),
+			     N_("read packs from stdin"),
+			     PARSE_OPT_OPTARG, parse_stdin_packs_mode),
 		OPT_BOOL(0, "stdin-packs", &stdin_packs,
 			 N_("read packs from stdin")),
 		OPT_BOOL(0, "stdout", &pack_to_stdout,
@@ -5010,9 +5064,10 @@ int cmd_pack_objects(int argc,
 		strvec_push(&rp, "--unpacked");
 	}
 
-	if (exclude_promisor_objects && exclude_promisor_objects_best_effort)
-		die(_("options '%s' and '%s' cannot be used together"),
-		    "--exclude-promisor-objects", "--exclude-promisor-objects-best-effort");
+	die_for_incompatible_opt2(exclude_promisor_objects,
+				  "--exclude-promisor-objects",
+				  exclude_promisor_objects_best_effort,
+				  "--exclude-promisor-objects-best-effort");
 	if (exclude_promisor_objects) {
 		use_internal_rev_list = 1;
 		fetch_if_missing = 0;
@@ -5050,22 +5105,23 @@ int cmd_pack_objects(int argc,
 	if (!pack_to_stdout && thin)
 		die(_("--thin cannot be used to build an indexable pack"));
 
-	if (keep_unreachable && unpack_unreachable)
-		die(_("options '%s' and '%s' cannot be used together"), "--keep-unreachable", "--unpack-unreachable");
+	die_for_incompatible_opt2(keep_unreachable, "--keep-unreachable",
+				  unpack_unreachable, "--unpack-unreachable");
 	if (!rev_list_all || !rev_list_reflog || !rev_list_index)
 		unpack_unreachable_expiration = 0;
 
-	if (stdin_packs && filter_options.choice)
-		die(_("cannot use --filter with --stdin-packs"));
+	die_for_incompatible_opt2(stdin_packs, "--stdin-packs",
+				  filter_options.choice, "--filter");
+
 
 	if (stdin_packs && use_internal_rev_list)
 		die(_("cannot use internal rev list with --stdin-packs"));
 
 	if (cruft) {
 		if (use_internal_rev_list)
 			die(_("cannot use internal rev list with --cruft"));
-		if (stdin_packs)
-			die(_("cannot use --stdin-packs with --cruft"));
+		die_for_incompatible_opt2(stdin_packs, "--stdin-packs",
+					  cruft, "--cruft");
 	}
 
 	/*
@@ -5133,11 +5189,7 @@ int cmd_pack_objects(int argc,
 		progress_state = start_progress(the_repository,
 						_("Enumerating objects"), 0);
 	if (stdin_packs) {
-		/* avoids adding objects in excluded packs */
-		ignore_packed_keep_in_core = 1;
-		read_packs_list_from_stdin();
-		if (rev_list_unpacked)
-			add_unreachable_loose_objects();
+		read_stdin_packs(stdin_packs, rev_list_unpacked);
 	} else if (cruft) {
 		read_cruft_objects();
 	} else if (!use_internal_rev_list) {