replace-object: move replace_map to object store

The relationship between an object X and another object Y that
replaces the object X is defined only within the scope of a
single repository.

The exception in reachability rule around these replacement objects
is also local to a repository (i.e. if traversal from refs reaches
X, then both X and Y are reachable and need to be kept from gc).

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object-store.h

@@ -1,6 +1,8 @@
 #ifndef OBJECT_STORE_H
 #define OBJECT_STORE_H
 
+#include "oidmap.h"
+
 struct alternate_object_database {
 	struct alternate_object_database *next;
 
@@ -93,6 +95,12 @@ struct raw_object_store {
 	struct alternate_object_database *alt_odb_list;
 	struct alternate_object_database **alt_odb_tail;
 
+	/*
+	 * Objects that should be substituted by other objects
+	 * (see git-replace(1)).
+	 */
+	struct oidmap replace_map;
+
 	/*
 	 * private data
 	 *

replace-object.h

@@ -0,0 +1,9 @@
+#ifndef REPLACE_OBJECT_H
+#define REPLACE_OBJECT_H
+
+struct replace_object {
+	struct oidmap_entry original;
+	struct object_id replacement;
+};
+
+#endif /* REPLACE_OBJECT_H */

replace_object.c

@@ -1,15 +1,11 @@
 #include "cache.h"
 #include "oidmap.h"
+#include "object-store.h"
+#include "replace-object.h"
 #include "refs.h"
+#include "repository.h"
 #include "commit.h"
 
-struct replace_object {
-	struct oidmap_entry original;
-	struct object_id replacement;
-};
-
-static struct oidmap replace_map = OIDMAP_INIT;
-
 static int register_replace_ref(const char *refname,
 				const struct object_id *oid,
 				int flag, void *cb_data)
@@ -29,7 +25,7 @@ static int register_replace_ref(const char *refname,
 	oidcpy(&repl_obj->replacement, oid);
 
 	/* Register new object */
-	if (oidmap_put(&replace_map, repl_obj))
+	if (oidmap_put(&the_repository->objects->replace_map, repl_obj))
 		die("duplicate replace ref: %s", refname);
 
 	return 0;
@@ -44,7 +40,7 @@ static void prepare_replace_object(void)
 
 	for_each_replace_ref(register_replace_ref, NULL);
 	replace_object_prepared = 1;
-	if (!replace_map.map.tablesize)
+	if (!the_repository->objects->replace_map.map.tablesize)
 		check_replace_refs = 0;
 }
 
@@ -67,7 +63,8 @@ const struct object_id *do_lookup_replace_object(const struct object_id *oid)
 
 	/* Try to recursively replace the object */
 	while (depth-- > 0) {
-		struct replace_object *repl_obj = oidmap_get(&replace_map, cur);
+		struct replace_object *repl_obj =
+			oidmap_get(&the_repository->objects->replace_map, cur);
 		if (!repl_obj)
 			return cur;
 		cur = &repl_obj->replacement;