Fix blame window heatmap alignment on resize

[Copilot]

The right-side heatmap indicators (vertical bars) in the blame window stay at their original fixed column when the window is resized with :wincmd >, causing them to appear misaligned in the middle of the expanded window.

Changes

• Add WinResized autocmd to detect blame window resizes and trigger extmark repositioning
• Add update_right_extmarks() to recalculate window width and reposition heatmap extmarks
• Extract set_right_extmark() helper to eliminate duplication between initial render and resize update

Implementation

Extmarks use virt_text_win_col to position at a specific column. On resize:

1. Get actual window width: nvim_win_get_width(blm_win) - 1 (0-indexed)
2. Delete extmarks with virt_text_win_col property
3. Recreate at new position

Pattern follows current_line_blame.lua's WinResized handling.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>blame window: right side extmarks stays untouched at wincmd ></issue_title>
<issue_description>### Description

When increasing the width of the blame window (to see long commit titles) right side extmarks (I'm not sure if it's called heatmap) no longer keep to the right side.

Neovim version

v0.12.0-dev-1050+g9467731865

Operating system and version

Debian Sid

Expected behavior

Right side extmarks are snapped to the right on WinResize.

Actual behavior

See the description

Minimal config

• notice no --depth=1 only - the rest is untouched.

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', 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
}

Steps to reproduce

• nvim --clean -u init.lua gitsigns_issue/gitsigns/lua/gitsigns/signs.lua
• :Gitsigns blame
• :5wincmd >

Gitsigns debug messages

:Gitsigns debug_messages
0.03 D dprintf: Deriving GitSignsAdd from Added
0.16 D derive: Deriving GitSignsChange from Changed
0.21 D derive: Deriving GitSignsDelete from Removed
0.31 D derive: Deriving GitSignsChangedelete from GitSignsChange
0.34 D derive: Deriving GitSignsTopdelete from GitSignsDelete
0.41 D derive: Deriving GitSignsUntracked from GitSignsAdd
0.47 D derive: Deriving GitSignsAddNr from GitSignsAdd
0.50 D derive: Deriving GitSignsChangeNr from GitSignsChange
0.52 D derive: Deriving GitSignsDeleteNr from GitSignsDelete
0.57 D derive: Deriving GitSignsChangedeleteNr from GitSignsChangeNr
0.59 D derive: Deriving GitSignsTopdeleteNr from GitSignsDeleteNr
0.62 D derive: Deriving GitSignsUntrackedNr from GitSignsAddNr
0.64 D derive: Deriving GitSignsAddLn from DiffAdd
0.67 D derive: Deriving GitSignsChangeLn from DiffChange
0.71 D derive: Deriving GitSignsChangedeleteLn from GitSignsChangeLn
0.75 D derive: Deriving GitSignsTopdeleteLn from GitSignsDeleteLn
0.82 D derive: Deriving GitSignsUntrackedLn from GitSignsAddLn
0.84 D derive: Deriving GitSignsAddCul from GitSignsAdd
0.88 D derive: Deriving GitSignsChangeCul from GitSignsChange
0.90 D derive: Deriving GitSignsDeleteCul from GitSignsDelete
0.92 D derive: Deriving GitSignsChangedeleteCul from GitSignsChangeCul
0.95 D derive: Deriving GitSignsTopdeleteCul from GitSignsDeleteCul
0.97 D derive: Deriving GitSignsUntrackedCul from GitSignsAddCul
1.01 D derive: Deriving GitSignsStagedAdd from GitSignsAdd
1.04 D derive: Deriving GitSignsStagedChange from GitSignsChange
1.07 D derive: Deriving GitSignsStagedDelete from GitSignsDelete
1.10 D derive: Deriving GitSignsStagedChangedelete from GitSignsChangedelete
1.12 D derive: Deriving GitSignsStagedTopdelete from GitSignsTopdelete
1.15 D derive: Deriving GitSignsStagedUntracked from GitSignsUntracked
1.23 D derive: Deriving GitSignsStagedAddNr from GitSignsAddNr
1.27 D derive: Deriving GitSignsStagedChangeNr from GitSignsChangeNr
1.30 D derive: Deriving GitSignsStagedDeleteNr from GitSignsDeleteNr
1.33 D derive: Deriving GitSignsStagedChangedeleteNr from GitSignsChangedeleteNr
1.37 D derive: Deriving GitSignsStagedTopdeleteNr from GitSignsTopdeleteNr
1.40 D derive: Deriving GitSignsStagedUntrackedNr from GitSignsUntrackedNr
1.42 D derive: Deriving GitSignsStagedAddLn from GitSignsAddLn
1.45 D derive: Deriving GitSignsStagedChangeLn from GitSignsChangeLn
1.49 D derive: Deriving GitSignsStagedChangedeleteLn from GitSignsChangedeleteLn
1.56 D derive: Could not derive GitSignsStagedTopdeleteLn
1.59 D derive: Deriving GitSignsStagedUntrackedLn from GitSignsUntrackedLn
1.62 D derive: Deriving GitSignsStagedAddCul from GitSignsAddCul
1.64 D derive: Deriving GitSignsStagedChangeCul from GitSignsChangeCul
1.73 D derive: Deriving GitSignsStagedDeleteCul from GitSignsDeleteCul
1.76 D derive: Deriving GitSignsStagedChangedeleteCul from GitSignsChangedeleteCul
1.79 D derive: Deriving GitSignsStagedTopdeleteCul from GitSignsTopdeleteCul
1.84 D derive: Deriving GitSignsStagedUntrackedCul from GitSignsUntrackedCul
1.89 D derive: Deriving GitSignsAddPreview from DiffAdd
1.92 D derive: Deriving GitSignsDeletePreview from DiffDelete
1.96 D derive: Deriving GitSignsCurrentLineBlame from NonText
2.01 D derive: Deriving GitSignsAddInline from TermCursor
2.04 D derive: Deriving GitSignsDeleteInline from TermCursor
2.07 D derive: Deriving GitSignsChangeInline from TermCursor
2.10 D derive: Deriving GitSignsAddLnInline from GitSignsAddInline
2.13 D derive: Deriving GitSignsChangeLnInline from Git...

</details>



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- Fixes lewis6991/gitsigns.nvim#1398

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