Merge branch 'jk/no-optional-locks'

Some commands (most notably "git status") makes an opportunistic
update when performing a read-only operation to help optimize later
operations in the same repository.  The new "--no-optional-locks"
option can be passed to Git to disable them.

* jk/no-optional-locks:
  git: add --no-optional-locks option

environment.c

@@ -338,3 +338,8 @@ void reset_shared_repository(void)
 {
 	need_shared_repository_from_config = 1;
 }
+
+int use_optional_locks(void)
+{
+	return git_env_bool(GIT_OPTIONAL_LOCKS_ENVIRONMENT, 1);
+}