filter duplicates on g:ctrlp_lines while preserving order

[timfeirg]

This closes #314, #168

This may not be the best implementation, but it should only affect performance when refreshing a very large :CtrlPMixed lists.

I have very little experience with vimL, the project code hasn't been easy for me to understand, I'm not very sure where and how to implement this at all, I'll be glad to take any advises and fix up my commit.

@mattn

[tacahiroy]

hmm - i still don't reproduce the issue actually

[timfeirg]

This would appear when one file appears in both files and MRU files at the same time.

steps to reproduce:

• navigate to a brand new directory with some files, not cached by ctrlp (or simply :CtrlPClearAllCaches)
• open up vim with ctrlp loaded
• :CtrlpMixed and open up one of the files
• re-open vim and launch :CtrlpMixed again, the file from the previous step will be duplicated, one from MRU, one from buffer.

I can firmly reproduce using the above steps.

@tacahiroy

[mattn]

Current implementation doesn't remove duplicates.

[timfeirg]

I've been using my own fork without a problem, didn't notice any performance regression, would you be interested in merging this PR? I mean, until a better implementation is introduced? @mattn

I think it's probably best to filter out duplicates just before the ctrlp pane is rendered, but I haven't been able to pinpoint the code that does this.

[mattn]

I want to look your diff. And figure out what is problem.

[timfeirg]

Dear developers, since #370 couldn't resolve this issue, would you be interested in merging this PR for the time being? We can, of course, revert this PR when a better implementation can be introduced.

Without duplicate filtering, :CtrlPMixed could display quite a lot of useless information, considering the default ctrlp pane is only 10 lines long, this behavior is very much wanted.

@mattn

[mattn]

Before merging, I want to reproduce this.

[timfeirg]

I'm on e66b5b5 and I can still reproduce this following the steps in #367 (comment)