on_lines handler reports wrong value for Visual Block

[MIvanchev]

Describe the bug

Create a buffer with some lines. Register an event handler with

local function on_lines(_, bufnr, changedtick, first, last, last_updated, _, _, _)
  print(bufnr .. ' ' .. changedtick .. ' ' .. first .. ' ' .. last .. ' ' .. last_updated)
end

vim.api.nvim_buf_attach(0, false, {
  on_lines = on_lines
})

Go to the beginning of line 1. Go into Visual Block (C-V), insert a space (Shift + I, then space, then Escape). I get <bufnr> <changedtick> 1 1 1. Deleting the space with with x results in <bufnr> <changedtick> 0 1 1 which is the correct result according to https://neovim.io/doc/user/api.html#nvim_buf_attach() (first value zero-indexed, rest probably not)

<bufnr> <changedtick> 1 1 1 is wrong and should be <bufnr> <changedtick> 0 1 1 (zero-based 1st line edited and was the only line edited, line number after edit is still 1.

Steps to reproduce

See description.

Expected behavior

See description.

Neovim version (nvim -v)

0.8.1

Vim (not Nvim) behaves the same?

no, neovim specifics

Operating system/version

Ubuntu 20.04

Terminal name/version

Neovim-qt

$TERM environment variable

n/a

Installation

Self-compiled