This patch adds a new configuration option (overlay_root) specifying 
what mount point opkg should check for available storage space.

Signed-off-by: Nicolas Thill <nico@openwrt.org>


--- a/libopkg/opkg_conf.c
+++ b/libopkg/opkg_conf.c
@@ -58,6 +58,7 @@
 	  { "noaction", OPKG_OPT_TYPE_BOOL, &_conf.noaction },
 	  { "nodeps", OPKG_OPT_TYPE_BOOL, &_conf.nodeps },
 	  { "offline_root", OPKG_OPT_TYPE_STRING, &_conf.offline_root },
+	  { "overlay_root", OPKG_OPT_TYPE_STRING, &_conf.overlay_root },
 	  { "proxy_passwd", OPKG_OPT_TYPE_STRING, &_conf.proxy_passwd },
 	  { "proxy_user", OPKG_OPT_TYPE_STRING, &_conf.proxy_user },
 	  { "query-all", OPKG_OPT_TYPE_BOOL, &_conf.query_all },
--- a/libopkg/opkg_conf.h
+++ b/libopkg/opkg_conf.h
@@ -74,6 +74,7 @@
      int check_signature;
      int nodeps; /* do not follow dependences */
      char *offline_root;
+     char *overlay_root;
      int query_all;
      int verbosity;
      int noaction;
--- a/libopkg/opkg_install.c
+++ b/libopkg/opkg_install.c
@@ -194,8 +194,11 @@
 	if (conf->force_space || pkg->installed_size == 0)
 		return 0;
 
-	root_dir = pkg->dest ? pkg->dest->root_dir :
-						conf->default_dest->root_dir;
+	root_dir = pkg->dest
+		? pkg->dest->root_dir
+		: conf->overlay_root
+			? conf->overlay_root
+			: conf->default_dest->root_dir;
 	kbs_available = get_available_kbytes(root_dir);
 
 	pkg_size_kbs = (pkg->installed_size + 1023)/1024;