Make completion for debugindex<tab><tab> show debugindexdot, too. The special handling for commands with names that are substrings of other commands (e.g. with st and strip) wasn't used with debug commands before.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m "test" -d "1000000 0"
hg verify
hg parents
hg status
hg undo
hg verify
hg parents
hg status