g:ctrlp_by_filename doesn't work

[12425]

Explanation of g:ctrlp_by_filename:

                                                        *'g:ctrlp_by_filename'*
Set this to 1 to set searching by filename (as opposed to full path) as the
default: >
  let g:ctrlp_by_filename = 0

To match filename only, the regex should

1. End with [^/]$
2. No / matches between input letters

Now I see the code is

    if a:mmode == 'filename-only'
        let s:matchregex .= '[\^\\]*'
    endif

If I input a, the regex will be \v\c[\^\\]*a
This is not correct.
The correct regex should be \v\ca[^/]*$
In Windows it should be \v\ca[^\\]*$

If I input ab, the regex will be \v\c[\^\\]*a[^a]*b
And it should be \v\ca[^a/]*b[^/]*$ to avoid / between a and b.

[12425]

A PR is created at #38.

[tracyone]

I can reproduce this issue