odb: get rid of `the_repository` when handling submodule sources

The "--recursive" flag for git-grep(1) allows users to grep for a string
across submodule boundaries. To make this work we add each submodule's
object sources to our own object database so that the objects can be
accessed directly.

The infrastructure for this depends on a global string list of submodule
paths. The caller is expected to call `add_submodule_odb_by_path()` for
each source and the object database will then eventually register all
submodule sources via `do_oid_object_info_extended()` in case it isn't
able to look up a specific object.

This reliance on global state is of course suboptimal with regards to
our libification efforts.

Refactor the logic so that the list of submodule sources is instead
tracked in the object database itself. This allows us to lose the
condition of `r == the_repository` before registering submodule sources
as we only ever add submodule sources to `the_repository` anyway. As
such, behaviour before and after this refactoring should always be the
same.

Rename the functions accordingly.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 31 insertions, 6 deletions

diff --git a/odb.c b/odb.c
index 4f03be7f77..f0b27bd936 100644
--- a/odb.c
+++ b/odb.c
@@ -24,6 +24,7 @@
 #include "strbuf.h"
 #include "strvec.h"
 #include "submodule.h"
+#include "trace2.h"
 #include "write-or-die.h"
 
 KHASH_INIT(odb_path_map, const char * /* key: odb_path */,
@@ -469,6 +470,12 @@ struct odb_source *odb_find_source(struct object_database *odb, const char *obj_
 	return source;
 }
 
+void odb_add_submodule_source_by_path(struct object_database *odb,
+				      const char *path)
+{
+	string_list_insert(&odb->submodule_source_paths, path);
+}
+
 static void fill_alternate_refs_command(struct child_process *cmd,
 					const char *repo_path)
 {
@@ -623,6 +630,23 @@ void disable_obj_read_lock(void)
 
 int fetch_if_missing = 1;
 
+static int register_all_submodule_sources(struct object_database *odb)
+{
+	int ret = odb->submodule_source_paths.nr;
+
+	for (size_t i = 0; i < odb->submodule_source_paths.nr; i++)
+		odb_add_to_alternates_memory(odb,
+					     odb->submodule_source_paths.items[i].string);
+	if (ret) {
+		string_list_clear(&odb->submodule_source_paths, 0);
+		trace2_data_intmax("submodule", odb->repo,
+				   "register_all_submodule_sources/registered", ret);
+		if (git_env_bool("GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB", 0))
+			BUG("register_all_submodule_sources() called");
+	}
+	return ret;
+}
+
 static int do_oid_object_info_extended(struct repository *r,
 				       const struct object_id *oid,
 				       struct object_info *oi, unsigned flags)
@@ -676,13 +700,12 @@ static int do_oid_object_info_extended(struct repository *r,
 		}
 
 		/*
-		 * If r is the_repository, this might be an attempt at
-		 * accessing a submodule object as if it were in the_repository
-		 * (having called add_submodule_odb() on that submodule's ODB).
-		 * If any such ODBs exist, register them and try again.
+		 * This might be an attempt at accessing a submodule object as
+		 * if it were in main object store (having called
+		 * `odb_add_submodule_source_by_path()` on that submodule's
+		 * ODB). If any such ODBs exist, register them and try again.
 		 */
-		if (r == the_repository &&
-		    register_all_submodule_odb_as_alternates())
+		if (register_all_submodule_sources(r->objects))
 			/* We added some alternates; retry */
 			continue;
 
@@ -968,6 +991,7 @@ struct object_database *odb_new(struct repository *repo)
 	INIT_LIST_HEAD(&o->packed_git_mru);
 	hashmap_init(&o->pack_map, pack_map_entry_cmp, NULL, 0);
 	pthread_mutex_init(&o->replace_mutex, NULL);
+	string_list_init_dup(&o->submodule_source_paths);
 	return o;
 }
 
@@ -1017,4 +1041,5 @@ void odb_clear(struct object_database *o)
 	o->packed_git = NULL;
 
 	hashmap_clear(&o->pack_map);
+	string_list_clear(&o->submodule_source_paths, 0);
 }