f() { COMPREPLY=(aaaaaaaaaaaaaa bbbbbbbbbbbbbb cccccccccccccc); }
complete -F f f
bind 'set completion-prefix-display-length 2'
$ f dddd [TAB][TAB]
...aaaaaaaaaa ...bbbbbbbbbb ...cccccccccc
None of the completion entries share a common prefix, though the docs
suggest that only common prefixes are removed:
The length in characters of the common prefix of a list of
possible completions
that is displayed without modification. When set to a value
greater than zero,
common prefixes longer than this value are replaced with an ellipsis when
displaying possible completions.
colored-completion-prefix has the same issue, in that it colors the
first n characters, where n is the length of the word being completed.
On a related note, colored-completion-prefix has no effect if
completion-prefix-display-length is greater than 0.