fix(buffers): select_current not selecting current buffer index

[pirey]

Description

When using builtin.buffers with select_current = true, it is not selecting current buffer.
This is because the current implementation tries to set the default_selection_idx using buffer number instead of buffer index.

The solution is to set default_selection_idx using buffer index.

Fixes #2917

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

:lua require('telescope.builtin').buffers({ select_current = true })

Configuration:

• Neovim version (nvim --version):

NVIM v0.10.0
Build type: Release
LuaJIT 2.1.1713484068

• Operating system and version: Windows 11 / WSL

Checklist:

• My code follows the style guidelines of this project (stylua)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (lua annotations)

[dam9000]

The fix looks good and I tested it. It fixed an issue that I also observed - select_current was working only for the files that were provided through the command line but not for any new files opened afterwards from within nvim. Now that works too.

[jamestrew]

thanks!