This is a bit different from show-all-if-ambiguous because
show-all-if-unmodified is used when the strings to complete don't have a
common prefix.
# Only one <tab> is necessary to get a list of all possible options.
set show-all-if-ambiguous on
# Only one <tab> is necessary to get a list of all possible options.
set show-all-if-ambiguous on
+set show-all-if-unmodified on
# Activate Vi editing mode.
set editing-mode vi
# Activate Vi editing mode.
set editing-mode vi