menu-complete gets stuck when new match dir is same length as previous match dir

[chrisant996]

menu-complete gets stuck when a previous match dir and new match dir are the same length.

REPRO:

• For example, in the clink repo, where clink\lib\ and clink\lua\ both exist.
• Type dir cli,menu-complete,l,menu-complete,menu-complete,s,menu-complete.

EXPECTED: completion is clink\lua\scripts\.
ACTUAL: nothing happens, because clink\lib\s* doesn't exist ("lib\s*" is used by mistake instead of "lua\s*").

This regression was introduced in the v1.0.0 rewrite, as part of the match_pipeline stuff.