feat: swap tab and btab direction when tmux-popup shows above the cursor

[zyf0330]

Do you think this is a good change?

[Aloxaf]

Quite reasonable.

[tardypad]

I think this commit should be reverted because it doesn't follow the usual behavior of fzf.
fzf doesn't invert the meaning of up and down actions depending on the layout.
So this brings inconsistencies in the usage of fzf.
For example when used in fzf-tab with a default layout (in this tmux popup over the cursor), tab goes up visually but in other instances, it would naturally go down.

Personnally this change broke the usage of fzf-tab because I force fzf to use reverse layout by default.

As a workaround I was trying to find a way via the options to overwrite this change but I couldn't find anything

[Aloxaf]

@tardypad
Thanks for your advice. I add a option named popup-smart-tab to control this behavior.
You can use zstyle ':fzf-tab:complete:*' popup-smart-tab false to disable it now.

[tardypad]

@Aloxaf Thanks for the really quick change.
I can live with this workaround :)