tmp-objdir: put quarantine information in the environment

The presence of the GIT_QUARANTINE_PATH variable lets any
called programs know that they're operating in a temporary
object directory (and where that directory is).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

tmp-objdir.c

@@ -147,6 +147,8 @@ struct tmp_objdir *tmp_objdir_create(void)
 	env_append(&t->env, ALTERNATE_DB_ENVIRONMENT,
 		   absolute_path(get_object_directory()));
 	env_replace(&t->env, DB_ENVIRONMENT, absolute_path(t->path.buf));
+	env_replace(&t->env, GIT_QUARANTINE_ENVIRONMENT,
+		    absolute_path(t->path.buf));
 
 	return t;
 }