Merge branch 'jt/grep-wo-submodule-odb-as-alternate'

The code to make "git grep" recurse into submodules has been
updated to migrate away from the "add submodule's object store as
an alternate object store" mechanism (which is suboptimal).

* jt/grep-wo-submodule-odb-as-alternate:
  t7814: show lack of alternate ODB-adding
  submodule-config: pass repo upon blob config read
  grep: add repository to OID grep sources
  grep: allocate subrepos on heap
  grep: read submodule entry with explicit repo
  grep: typesafe versions of grep_source_init
  grep: use submodule-ODB-as-alternate lazy-addition
  submodule: lazily add submodule ODBs as alternates

object-file.c

@@ -32,6 +32,7 @@
 #include "packfile.h"
 #include "object-store.h"
 #include "promisor-remote.h"
+#include "submodule.h"
 
 /* The maximum size for an object header. */
 #define MAX_HEADER_LEN 32
@@ -1613,6 +1614,10 @@ static int do_oid_object_info_extended(struct repository *r,
 				break;
 		}
 
+		if (register_all_submodule_odb_as_alternates())
+			/* We added some alternates; retry */
+			continue;
+
 		/* Check if it is a missing object */
 		if (fetch_if_missing && repo_has_promisor_remote(r) &&
 		    !already_retried &&