fix(vim.fs): joinpath() should ignore empty items #38077

Problem:
vim.fs.joinpath treats empty string as a path segment
(it adds a path separator for each empty item):

    print(vim.fs.joinpath('', 'after/lsp', '')) -- '/after/lsp/'
    print(vim.fs.joinpath('', '')) -- '/'

Especially problematic if the empty segment is the first segment, as
that converts the path to an absolute path.

Solution:
Ignore empty (length of 0) path segments.

Benchmark:

    local function test(func)
      local t = vim.uv.hrtime()
      for _ = 1, 100000, 1 do
        func('', 'this/is', 'a/very/long/path', '', 'it', 'really', 'is')
      end
      print(math.floor((vim.uv.hrtime() - t) / 1e6), 'ms')
    end

- with Iter():filter() --> 370 ms
- building new segments table --> 208 ms
- with vim.tbl_filter --> 232 ms
- Instead of gsub split on `/` in all parts --> 1870 ms

0 files changed, 0 insertions, 0 deletions