When scrolling line by line, the blame window does not scroll with the main window

[ofseed]

Description

:Gitsigns blame add gaps to the main window when the diff is smaller than two lines. I found that when scrolling line by line using j or <C-e>, the blame window will not follow the scroll when the one gap is scrolled out of the screen.

_20240625_203753.webm

Neovim version

NVIM v0.11.0-dev-3461+g9e436251d (latest master currently)

Operating system and version

6.9.6-arch1-1

Expected behavior

The two windows should scroll together and be always aligned.

Actual behavior

If it is a gap rather than a line of text be scrolled out the screen, the blame window will not be scroll following the main window.

Minimal config

for name, url in pairs{
  gitsigns = 'https://github.com/lewis6991/gitsigns.nvim',
  -- ADD OTHER PLUGINS _NECESSARY_ TO REPRODUCE THE ISSUE
} do
local install_path = vim.fn.fnamemodify('gitsigns_issue/'..name, ':p')
if vim.fn.isdirectory(install_path) == 0 then
vim.fn.system { 'git', 'clone', '--depth=1', url, install_path }
end
vim.opt.runtimepath:append(install_path)
end

require('gitsigns').setup{
  debug_mode = true, -- You must add this to enable debug messages
  -- ADD GITSIGNS CONFIG THAT IS _NECESSARY_ FOR REPRODUCING THE ISSUE
}

-- ADD INIT.LUA SETTINGS THAT IS _NECESSARY_ FOR REPRODUCING THE ISSUE

Steps to reproduce

1. Clone gitsigns.nvim
2. Create minimal.lua in place and save it after copying its content
3. Open a file of the gitsigns.nvim repo by nvim -u minimal.lua lua/gitsigns.lua
4. Scroll line by line

Gitsigns debug messages

No response

Gitsigns cache

No response

[lewis6991]

Gitsigns just uses set scrollbind in each window. This is probably a limitation of virtual_lines in Neovim. I don't think we can fix that here.

[ofseed]

I also guessed that it might be an upstream problem, but there will not be this issue when just using diff-mode, which utilizes set scrollbind too. I have no idea how to make it work properly.

[lewis6991]

Diff mode doesn't use extmarks and injects filler lines directly.

[lewis6991]

Raised neovim/neovim#29751 . Not sure what we can do to mitigate this in the meantime other than removing the virtual lines.

[ofseed]

The upstream fix works well, thank you for your great work!