This needs a version newer than 0.15 (it's a noop on older versions).
# Close current view like in mutt.
bind diff i view-close
# Close current view like in mutt.
bind diff i view-close
+# Unbind commands which may change the repository. I use tig only as a viewer.
+bind generic u none
+bind generic ! none
+bind generic M none
+bind generic @ none
+bind generic e none
+bind generic G none
+bind generic C none
+bind generic i none
+