Merge branch 'jk/check-connected-with-alternates'

The tips of refs from the alternate object store can be used as
starting point for reachability computation now.

* jk/check-connected-with-alternates:
  check_everything_connected: assume alternate ref tips are valid
  object-store.h: move for_each_alternate_ref() from transport.h

Documentation/rev-list-options.txt

@@ -182,6 +182,14 @@ explicitly.
 	Pretend as if all objects mentioned by reflogs are listed on the
 	command line as `<commit>`.
 
+--alternate-refs::
+	Pretend as if all objects mentioned as ref tips of alternate
+	repositories were listed on the command line. An alternate
+	repository is any repository whose object directory is specified
+	in `objects/info/alternates`.  The set of included objects may
+	be modified by `core.alternateRefsCommand`, etc. See
+	linkgit:git-config[1].
+
 --single-worktree::
 	By default, all working trees will be examined by the
 	following options when there are more than one (see

builtin/receive-pack.c

@@ -12,7 +12,6 @@
 #include "object.h"
 #include "remote.h"
 #include "connect.h"
-#include "transport.h"
 #include "string-list.h"
 #include "sha1-array.h"
 #include "connected.h"

connected.c

@@ -80,6 +80,7 @@ int check_connected(oid_iterate_fn fn, void *cb_data,
 		argv_array_push(&rev_list.args, "--all");
 	}
 	argv_array_push(&rev_list.args, "--quiet");
+	argv_array_push(&rev_list.args, "--alternate-refs");
 	if (opt->progress)
 		argv_array_pushf(&rev_list.args, "--progress=%s",
 				 _("Checking connectivity"));

object-store.h

@@ -33,6 +33,8 @@ void prepare_alt_odb(struct repository *r);
 char *compute_alternate_path(const char *path, struct strbuf *err);
 typedef int alt_odb_fn(struct object_directory *, void *);
 int foreach_alt_odb(alt_odb_fn, void*);
+typedef void alternate_ref_fn(const struct object_id *oid, void *);
+void for_each_alternate_ref(alternate_ref_fn, void *);
 
 /*
  * Add the directory to the on-disk alternates file; the new entry will also

revision.c

@@ -1554,6 +1554,32 @@ void add_index_objects_to_pending(struct rev_info *revs, unsigned int flags)
 	free_worktrees(worktrees);
 }
 
+struct add_alternate_refs_data {
+	struct rev_info *revs;
+	unsigned int flags;
+};
+
+static void add_one_alternate_ref(const struct object_id *oid,
+				  void *vdata)
+{
+	const char *name = ".alternate";
+	struct add_alternate_refs_data *data = vdata;
+	struct object *obj;
+
+	obj = get_reference(data->revs, name, oid, data->flags);
+	add_rev_cmdline(data->revs, obj, name, REV_CMD_REV, data->flags);
+	add_pending_object(data->revs, obj, name);
+}
+
+static void add_alternate_refs_to_pending(struct rev_info *revs,
+					  unsigned int flags)
+{
+	struct add_alternate_refs_data data;
+	data.revs = revs;
+	data.flags = flags;
+	for_each_alternate_ref(add_one_alternate_ref, &data);
+}
+
 static int add_parents_only(struct rev_info *revs, const char *arg_, int flags,
 			    int exclude_parent)
 {
@@ -1956,6 +1982,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	    !strcmp(arg, "--no-walk") || !strcmp(arg, "--do-walk") ||
 	    !strcmp(arg, "--bisect") || starts_with(arg, "--glob=") ||
 	    !strcmp(arg, "--indexed-objects") ||
+	    !strcmp(arg, "--alternate-refs") ||
 	    starts_with(arg, "--exclude=") ||
 	    starts_with(arg, "--branches=") || starts_with(arg, "--tags=") ||
 	    starts_with(arg, "--remotes=") || starts_with(arg, "--no-walk="))
@@ -2442,6 +2469,8 @@ static int handle_revision_pseudo_opt(const char *submodule,
 		add_reflogs_to_pending(revs, *flags);
 	} else if (!strcmp(arg, "--indexed-objects")) {
 		add_index_objects_to_pending(revs, *flags);
+	} else if (!strcmp(arg, "--alternate-refs")) {
+		add_alternate_refs_to_pending(revs, *flags);
 	} else if (!strcmp(arg, "--not")) {
 		*flags ^= UNINTERESTING | BOTTOM;
 	} else if (!strcmp(arg, "--no-walk")) {

sha1-file.c

@@ -743,6 +743,103 @@ out:
 	return ref_git;
 }
 
+static void fill_alternate_refs_command(struct child_process *cmd,
+					const char *repo_path)
+{
+	const char *value;
+
+	if (!git_config_get_value("core.alternateRefsCommand", &value)) {
+		cmd->use_shell = 1;
+
+		argv_array_push(&cmd->args, value);
+		argv_array_push(&cmd->args, repo_path);
+	} else {
+		cmd->git_cmd = 1;
+
+		argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path);
+		argv_array_push(&cmd->args, "for-each-ref");
+		argv_array_push(&cmd->args, "--format=%(objectname)");
+
+		if (!git_config_get_value("core.alternateRefsPrefixes", &value)) {
+			argv_array_push(&cmd->args, "--");
+			argv_array_split(&cmd->args, value);
+		}
+	}
+
+	cmd->env = local_repo_env;
+	cmd->out = -1;
+}
+
+static void read_alternate_refs(const char *path,
+				alternate_ref_fn *cb,
+				void *data)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	struct strbuf line = STRBUF_INIT;
+	FILE *fh;
+
+	fill_alternate_refs_command(&cmd, path);
+
+	if (start_command(&cmd))
+		return;
+
+	fh = xfdopen(cmd.out, "r");
+	while (strbuf_getline_lf(&line, fh) != EOF) {
+		struct object_id oid;
+		const char *p;
+
+		if (parse_oid_hex(line.buf, &oid, &p) || *p) {
+			warning(_("invalid line while parsing alternate refs: %s"),
+				line.buf);
+			break;
+		}
+
+		cb(&oid, data);
+	}
+
+	fclose(fh);
+	finish_command(&cmd);
+}
+
+struct alternate_refs_data {
+	alternate_ref_fn *fn;
+	void *data;
+};
+
+static int refs_from_alternate_cb(struct object_directory *e,
+				  void *data)
+{
+	struct strbuf path = STRBUF_INIT;
+	size_t base_len;
+	struct alternate_refs_data *cb = data;
+
+	if (!strbuf_realpath(&path, e->path, 0))
+		goto out;
+	if (!strbuf_strip_suffix(&path, "/objects"))
+		goto out;
+	base_len = path.len;
+
+	/* Is this a git repository with refs? */
+	strbuf_addstr(&path, "/refs");
+	if (!is_directory(path.buf))
+		goto out;
+	strbuf_setlen(&path, base_len);
+
+	read_alternate_refs(path.buf, cb->fn, cb->data);
+
+out:
+	strbuf_release(&path);
+	return 0;
+}
+
+void for_each_alternate_ref(alternate_ref_fn fn, void *data)
+{
+	struct alternate_refs_data cb;
+	cb.fn = fn;
+	cb.data = data;
+	foreach_alt_odb(refs_from_alternate_cb, &cb);
+}
+
 int foreach_alt_odb(alt_odb_fn fn, void *cb)
 {
 	struct object_directory *ent;

t/perf/p5600-clone-reference.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+
+test_description='speed of clone --reference'
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+test_expect_success 'create shareable repository' '
+	git clone --bare . shared.git
+'
+
+test_expect_success 'advance base repository' '
+	# Do not use test_commit here; its test_tick will
+	# use some ancient hard-coded date. The resulting clock
+	# skew will cause pack-objects to traverse in a very
+	# sub-optimal order, skewing the results.
+	echo content >new-file-that-does-not-exist &&
+	git add new-file-that-does-not-exist &&
+	git commit -m "new commit"
+'
+
+test_perf 'clone --reference' '
+	rm -rf dst.git &&
+	git clone --no-local --bare --reference shared.git . dst.git
+'
+
+test_done

t/t5618-alternate-refs.sh

@@ -0,0 +1,60 @@
+#!/bin/sh
+
+test_description='test handling of --alternate-refs traversal'
+. ./test-lib.sh
+
+# Avoid test_commit because we want a specific and known set of refs:
+#
+#  base -- one
+#      \      \
+#       two -- merged
+#
+# where "one" and "two" are on separate refs, and "merged" is available only in
+# the dependent child repository.
+test_expect_success 'set up local refs' '
+	git checkout -b one &&
+	test_tick &&
+	git commit --allow-empty -m base &&
+	test_tick &&
+	git commit --allow-empty -m one &&
+	git checkout -b two HEAD^ &&
+	test_tick &&
+	git commit --allow-empty -m two
+'
+
+# We'll enter the child repository after it's set up since that's where
+# all of the subsequent tests will want to run (and it's easy to forget a
+# "-C child" and get nonsense results).
+test_expect_success 'set up shared clone' '
+	git clone -s . child &&
+	cd child &&
+	git merge origin/one
+'
+
+test_expect_success 'rev-list --alternate-refs' '
+	git rev-list --remotes=origin >expect &&
+	git rev-list --alternate-refs >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rev-list --not --alternate-refs' '
+	git rev-parse HEAD >expect &&
+	git rev-list HEAD --not --alternate-refs >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'limiting with alternateRefsPrefixes' '
+	test_config core.alternateRefsPrefixes refs/heads/one &&
+	git rev-list origin/one >expect &&
+	git rev-list --alternate-refs >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --source shows .alternate marker' '
+	git log --oneline --source --remotes=origin >expect.orig &&
+	sed "s/origin.* /.alternate /" <expect.orig >expect &&
+	git log --oneline --source --alternate-refs >actual &&
+	test_cmp expect actual
+'
+
+test_done

transport.c

@@ -1380,100 +1380,3 @@ char *transport_anonymize_url(const char *url)
 literal_copy:
 	return xstrdup(url);
 }
-
-static void fill_alternate_refs_command(struct child_process *cmd,
-					const char *repo_path)
-{
-	const char *value;
-
-	if (!git_config_get_value("core.alternateRefsCommand", &value)) {
-		cmd->use_shell = 1;
-
-		argv_array_push(&cmd->args, value);
-		argv_array_push(&cmd->args, repo_path);
-	} else {
-		cmd->git_cmd = 1;
-
-		argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path);
-		argv_array_push(&cmd->args, "for-each-ref");
-		argv_array_push(&cmd->args, "--format=%(objectname)");
-
-		if (!git_config_get_value("core.alternateRefsPrefixes", &value)) {
-			argv_array_push(&cmd->args, "--");
-			argv_array_split(&cmd->args, value);
-		}
-	}
-
-	cmd->env = local_repo_env;
-	cmd->out = -1;
-}
-
-static void read_alternate_refs(const char *path,
-				alternate_ref_fn *cb,
-				void *data)
-{
-	struct child_process cmd = CHILD_PROCESS_INIT;
-	struct strbuf line = STRBUF_INIT;
-	FILE *fh;
-
-	fill_alternate_refs_command(&cmd, path);
-
-	if (start_command(&cmd))
-		return;
-
-	fh = xfdopen(cmd.out, "r");
-	while (strbuf_getline_lf(&line, fh) != EOF) {
-		struct object_id oid;
-		const char *p;
-
-		if (parse_oid_hex(line.buf, &oid, &p) || *p) {
-			warning(_("invalid line while parsing alternate refs: %s"),
-				line.buf);
-			break;
-		}
-
-		cb(&oid, data);
-	}
-
-	fclose(fh);
-	finish_command(&cmd);
-}
-
-struct alternate_refs_data {
-	alternate_ref_fn *fn;
-	void *data;
-};
-
-static int refs_from_alternate_cb(struct object_directory *e,
-				  void *data)
-{
-	struct strbuf path = STRBUF_INIT;
-	size_t base_len;
-	struct alternate_refs_data *cb = data;
-
-	if (!strbuf_realpath(&path, e->path, 0))
-		goto out;
-	if (!strbuf_strip_suffix(&path, "/objects"))
-		goto out;
-	base_len = path.len;
-
-	/* Is this a git repository with refs? */
-	strbuf_addstr(&path, "/refs");
-	if (!is_directory(path.buf))
-		goto out;
-	strbuf_setlen(&path, base_len);
-
-	read_alternate_refs(path.buf, cb->fn, cb->data);
-
-out:
-	strbuf_release(&path);
-	return 0;
-}
-
-void for_each_alternate_ref(alternate_ref_fn fn, void *data)
-{
-	struct alternate_refs_data cb;
-	cb.fn = fn;
-	cb.data = data;
-	foreach_alt_odb(refs_from_alternate_cb, &cb);
-}

transport.h

@@ -262,6 +262,4 @@ int transport_refs_pushed(struct ref *ref);
 void transport_print_push_status(const char *dest, struct ref *refs,
 		  int verbose, int porcelain, unsigned int *reject_reasons);
 
-typedef void alternate_ref_fn(const struct object_id *oid, void *);
-void for_each_alternate_ref(alternate_ref_fn, void *);
 #endif