replace-objects: create wrapper around setting

The 'read_replace_objects' constant is initialized by git_default_config
(if core.useReplaceRefs is disabled) and within setup_git_env (if
GIT_NO_REPLACE_OBJECTS) is set. To ensure that this variable cannot be
set accidentally in other places, wrap it in a replace_refs_enabled()
method.

Since we still assign this global in config.c, we are not able to remove
the global scope of this variable and make it a static within
replace-object.c. This will happen in a later change which will also
prevent the variable from being read before it is initialized.

Centralizing read access to the variable is an important first step.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/replace-object.h b/replace-object.h
index 7786d4152b..3e9c3516c3 100644
--- a/replace-object.h
+++ b/replace-object.h
@@ -28,6 +28,18 @@ const struct object_id *do_lookup_replace_object(struct repository *r,
 						 const struct object_id *oid);
 
 /*
+ * Some commands disable replace-refs unconditionally, and otherwise each
+ * repository could alter the core.useReplaceRefs config value.
+ *
+ * Return 1 if and only if all of the following are true:
+ *
+ *  a. disable_replace_refs() has not been called.
+ *  b. GIT_NO_REPLACE_OBJECTS is unset or zero.
+ *  c. the given repository does not have core.useReplaceRefs=false.
+ */
+int replace_refs_enabled(struct repository *r);
+
+/*
  * If object sha1 should be replaced, return the replacement object's
  * name (replaced recursively, if necessary).  The return value is
  * either sha1 or a pointer to a permanently-allocated value.  When
@@ -41,7 +53,7 @@ const struct object_id *do_lookup_replace_object(struct repository *r,
 static inline const struct object_id *lookup_replace_object(struct repository *r,
 							    const struct object_id *oid)
 {
-	if (!read_replace_refs ||
+	if (!replace_refs_enabled(r) ||
 	    (r->objects->replace_map_initialized &&
 	     r->objects->replace_map->map.tablesize == 0))
 		return oid;