[sbuild::chroot_union] Rework union mounts

Rename from fs_union to union.
Make configuration options more user friendly.
Update documentation to be more clear.

1 files changed, 3 insertions, 0 deletions

diff --git a/TODO b/TODO
index 261afedc..2b3b4be3 100644
--- a/TODO
+++ b/TODO
@@ -91,3 +91,6 @@ have
 
 file: Set full unpack dir with session ID like LVM snapshot.
 
+* Add a read-only mount option for union underlay (both for
+  devices and bind mounts).
+